Use of a portable field-adapted liquid chromatographic system (C-Vue machine) to estimate the quantity of deltamethrin on insecticide-treated nets paired with WHO cone bioassays to determine ITN bioefficacy as part of three-year durability monitoring in Mali

Use of a portable field-adapted liquid chromatographic system (C-Vue machine) to estimate the quantity of deltamethrin on insecticide-treated nets paired with WHO cone bioassays to determine ITN bioefficacy as part of three-year durability monitoring in Mali | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Use of a portable field-adapted liquid chromatographic system (C-Vue machine) to estimate the quantity of deltamethrin on insecticide-treated nets paired with WHO cone bioassays to determine ITN bioefficacy as part of three-year durability monitoring in Mali Moussa BM Cisse, Ibrahim Troare, Mamadou Sow, Yacouba Dansoko, and 14 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4749503/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background Monitoring insecticide levels and physical integrity over time is essential for assessing the durability of insecticide-treated nets (ITNs), which largely depends on the net handling habits of users. This study aimed to determine the insecticide content and effectiveness of ITNs (Yorkool and PermaNet 2.0) at 6, 12, 24 and 36 months after mass distribution in Mali. Methods At 12, 24 and 36 months postdistribution from 2018 to 2020, 30 nets were randomly collected from households in the districts of Kenieba and Kita in the southern part of Mali, together with information about ITN use and washing practices. The insecticidal effectiveness of the ITNs was assessed with the World Health Organization (WHO) cone test using a laboratory-reared susceptible colony of Anopheles coluzzii . The residual insecticide content was measured by a nondestructive sampling technique with a portable field-adapted liquid chromatographic system (C-Vue®) validated by running samples in parallel with standardized WHO HPLC methods. Results At each time point, nets were washed an average of three times over the previous 6 months, most commonly using detergent or bleach. For Yorkool nets, the average deltamethrin concentration was 55 mg/m 2 at 6 months and gradually decreased to 14 mg/m 2 at 36 months. The values for the PermaNet 2.0 nets were 45 mg/m 2 at 6 months and 6 mg/m 2 at 36 months. Until the 24-month evaluation, the proportion of nets with minimal effectiveness (at least 75% Knock Down "K.D." or 50% 24 h mortality) was greater than 80% for both net types and sites. According to the WHO criteria, the proportion of net who met the WHO optimal effectiveness criteria (at least 95% K.D. or 80% mortality) was less than 80%. The WHO standardized cone test and C-Vue evaluation demonstrated that net type effectiveness and insecticide content were consistently lower than expected at 3 years. Conclusion The nets did not meet the WHO criteria of optimal effectiveness for the efficacy of ITNs in this 3-year survey, and users washed nets with local soap containing detergent or bleach. The C-Vue portable chromatographic device was used successfully for the first time in Mali to measure the insecticide concentration of ITNs. These results were consistent with those of cone bioassays. Entomology Insecticide-treated nets minimal effectiveness optimal effectiveness insecticide content field-adapted liquid chromatographic system C-Vue® Figures Figure 1 Figure 2 Figure 3 Background Insecticide-treated nets (ITNs) play a significant role in preventing and controlling vector-borne diseases, especially malaria. They provide personal protection and can reduce transmission and protect an entire community (i.e., a mass effect) in settings with sustained high levels of coverage and anthropophilic vectors [ 1 , 2 ]. ITNs provide both a physical barrier and repellent protection through insecticides. For malaria control with ITNs, the World Health Organization (WHO) currently recommends universal coverage of one ITN for every two people in a household [ 3 ]. In many current ITN distribution programs, it is assumed that ITNs have a relatively uniform lifespan of approximately 3 years. Thus, it is often assumed that mass distribution campaigns at 3-year intervals are sufficient to maintain adequate net coverage levels throughout the 3-year interval [ 4 ]. Distributing additional nets through routine immunization programs or prenatal services is also recommended. However, recent longitudinal studies and surveys have revealed that this assumption of a uniform 3-year lifespan may be overly optimistic and that the rate at which net coverage declines after a campaign may be substantially more variable and more rapid than previously assumed. Therefore, the WHO now recommends that the delivery of ITNs through immunization and antenatal services be given as much priority as delivery through periodic campaigns [ 3 ]. ITNs are a key component of the malaria vector control strategy in Mali, where donors such as the U.S. President's Malaria Initiative (PMI) and Global Fund (G.F.) have distributed millions of nets since program implementation began in 2007 [ 5 ]. ITN distribution strategies in Mali are based on providing access through mass distribution campaigns to the entire target population at a rate of 2 people per net, as well as routine distribution to pregnant women and children under one year of age during prenatal consultations for women and the Expanded Program on Immunization for Children [ 4 , 6 ]. These strategies are reinforced by educational communication encouraging net care and use at the community level. Mali began with the ITN mass distribution campaign in 2011. Due to the difficulties in mobilizing the resources to cover all countries in one campaign in 2011, the National Malaria Control Program (NMCP) organized a region-by-region mass campaign distribution according to the national strategic plan. The NMCP organized at least one campaign in each region and Bamako District from 2011 to 2018 [ 7 ], and an interval of 3 years was established between campaigns in each region. Progress has been particularly impressive in increasing ITN coverage, as 90% of households in Mali have at least one ITN, and 55% of households have one ITN for two persons [ 7 ]. The first ITN durability monitoring in Mali was undertaken from 2014 to 2016 with four types of ITNs (PermaNet 2.0, PermaNet 3.0, Olyset Net, and OlysetPlus Net) in two districts: Sélingué and Bougouni, which are located in the southern Mali region of Sikasso. Among the results of that study, the proportionate hole index 36 months after the net distribution was much lower in PermaNet 2.0 and PermaNet 3.0 than in Olyset Net and OlysetPlus Net [ 8 ]. Mali’s NMCP planning for long-term coverage with ITNs requires information on the durability of different ITN products in local settings to choose which products to procure and to determine whether particular products are likely to perform best over time in a given setting. This also informs the necessary rate of replacement in continuous distribution systems, the appropriate interval between campaigns and, when necessary, plans for disposal or recycling of old nets. Monitoring the durability of nets may lead to a better understanding of the factors that determine ITN durability and the laboratory indicators that correlate with these net qualities. It can also provide an opportunity to improve behavior and communication messages so that users can take better care of their ITNs [ 3 ]. The WHO and Vector Control Technical Expert Group (VCTEG) guidelines describe methods for assessing ITN durability based on net attrition, insecticide content, insecticidal activity, and physical integrity [ 9 , 10 ]. Insecticide levels on ITNs are typically analyzed using a straight-phase high-performance liquid chromatography (HPLC) technique recommended by the Collaborative International Pesticides Analytical Council (CIPAC). The expense of the instrument and the reagents required for the analysis precludes many malaria-endemic resource-limited countries from carrying out proper monitoring of deltamethrin levels. Therefore, there is a need to develop a method that uses a portable and inexpensive liquid chromatographic device along with a nondestructive sampling technique to measure deltamethrin levels on deltamethrin-coated polyester nets. The importance of physical and insecticidal net durability is recognized as a critical factor, and a malaria control program needs to know how to determine the frequency at which nets should be replaced and the type of nets to be procured. This study assessed the insecticidal (bioefficacy and insecticide content) durability of ITNs (Yorkool and PermaNet 2.0) in two villages at 6, 12, 24, and 36 months after a net mass distribution was carried out in December 2017. The objectives of this study were to 1) determine the net use and washing practices within the communities, 2) assess the insecticidal effectiveness using the WHO cone bioassays test method, and 3) estimate the insecticidal content using the C-Vue HPLC method. Method Study sites and period The ITN mass campaign in the Kayes Region was conducted in December 2017, and data collection was conducted between March and May 2018 at an average of 6 months postdistribution as a baseline, at 12 months (December 2018), 24 months (November-December 2019) and 36 months (November-December 2020). The study was carried out in the districts of Kenieba and Kita, located in the Kayes Region, at sites with similar malaria epidemiological, climatic and socioecological profiles. For the selection of clusters, the campaign ITN distribution registries were used at both sites. A cluster was defined as a community, and the selection was performed with probability proportionate to size, with the number of ITNs distributed per community as the measure of size. In each of the districts, 15 clusters (village) were selected, and a grape (group of 5 households) was selected in each (Fig. 1 ). ITN Brands Yorkool nets were monitored in Kenieba, and PermaNet 2.0 nets were monitored in Kita, as those were the brands procured and distributed in each region. The technical specifications of the ITNs (material, textile specific, insecticide with concentration) are the same for the two brands, except that Yorkool nets are 75-denier and PermaNet 2.0 is 100-denier (a measure of fabric thickness). Both nets are made of knitted polyfilament polyester fibers and are treated with deltamethrin to a target concentration of 55 mg/m2 (WHO, 2021). Study Design This study is a part of the ITN durability monitoring project [ 12 ], and it is a prospective longitudinal study of a cohort of nets distributed in December 2017 as part of a mass distribution campaign. Sampling was carried out in 15 clusters (from villages) per study site (Heath District), and each cluster contained 1 grape (5 households). Within a few months following distribution (from March to May 2018), a household survey was carried out at each study site to identify representative households that received campaign nets and request that owners consent to participate in the study. Campaign nets from consenting households were selected to constitute the cohorts of nets for the three-year study period. These nets were labeled with a unique code at baseline (within 6 months postdistribution). At each period (baseline, 12, 24, and 36 months) (Fig. 2), 30 campaign nets per site (Health District) were selected for insecticide effectiveness testing (bioassays and chemical residue). Figure 2. Study design from 2017 to 2020 Nets Sampling At baseline, a cohort of ten (15) nets per cluster was tagged for eventual follow-up and removal at the 12-24- and 36-month assessments. Using a separate group of two-digit tags (A1-A6, B1-B6, etc.), households were selected randomly at baseline. One net in each of these households was tagged for follow-up at 6, 12, and 24 months, and the GPS location of the household was recorded. Following the WHO recommendation for phase III testing of ITNs (WHO, 2013b), random samples of 30 campaign nets per site (a total of 60) were selected at each annual assessment. Households were given a new ITN as a replacement. The collected nets were labeled and stored in separate plastic bags for transportation. Determination of net use and washing practices within communities Following the WHO [ 10 ] and U.S. President Malaria Initiative [ 12 ] guidelines, a one-page questionnaire confirming that the net was received during the campaign and obtaining basic information on net use, storage and washing patterns was administered to each participating household at the 6-month (baseline), 12-month, 24-month and 36-month assessments. Electronic data captured using Samsung Galaxy Tab A devices with ODK questionnaires were used to allow detailed programming of skip patterns and internal controls to ensure that the necessary data were consistent and complete. Determination of insecticidal effectiveness using the WHO Cone Following WHO guidelines [ 10 ], the insecticidal activity (biological efficacy) of the ITNs was determined with WHO cone tests using the susceptible mosquito Anopheles coluzzii Ngousso reared in a local insectary at LBMA. For each assessment period, 6-, 12-, 24- and 36-month bioassays were conducted with five pieces of netting measuring 25 × 25 cm, with 10 mosquitoes exposed on each piece of netting (total = 50 mosquitoes per net). Mortality and knockdown (KD) rates were used to evaluate the bioefficacy of the nets. Determination of insecticidal content using HPLC The same pieces of nets from the 6-, 12-, 24- and 36-month assessments of insecticidal activity were used for the determination of insecticide surface levels with the portable HPLC C-Vue (C-Vue® Portable Liquid Chromatograph Model CH2B) following the method described by [ 13 ]. Briefly, values generated by C-Vue chromatography are surface levels (S.L.) of deltamethrin obtained by rubbing the net with filter paper, which is nondestructive to the nets, and analyzing the residue through liquid chromatography. This method allows us to estimate the mean and median levels of active ingredients (insecticides) in mg/m2 across the net samples. These values are later compared with manufacturer specifications for the insecticide content of each net brand. A conversion equation was used to estimate the total level (T.L.) of insecticide from the mean surface level (S.L.): T.L. = (Log(SL) + 1.37)/0.0232). This equation was obtained through laboratory replication and 2 independent C-values and validated with gold standard HPLC [ 13 ]. Data analysis Once data collection for 6-, 12-, 24-, and 36-month rounds were completed and the data were verified, the data were transferred to a statistical software package (STATA for Windows, Version 14.0) for further consistency checks and preparation for analysis. The data analysis was conducted by using Stata do files (macros). The chi-square test was used for the comparison of proportions and mean values between the two sites. According to the World Health Organization Pesticide Evaluation Scheme (WHOPES) Phase III evaluation criteria, at least 80% of recommended ITN brands should achieve optimal effectiveness 36 months postdistribution. The following criteria were used to determine the optimal effectiveness of the nets: KD 60 mn ≥ 95% or mortality ≥ 80% and minimal effectiveness: KD60 mn ≥ 75% or mortality ≥ 50%. The surface level and the total level of insecticides from each assessment period were compared by using a t test. Results Net use practices The patter nets of users, storage place, type of sleeping place, and type of washing are among the critical factors that contribute to physical deterioration of bednets. The locations of nets (hanging loose and folded/tied and not hanging) were the same at both sites (> 20.0%) at 12 months ( p = 0.0660 ) and 36 months ( p = 0.2136 ) but differed between Kenieba and Kita ( p = 0.0012 ) at 24 months (Table 1 ). The proportion of net hanging loose decreased from 12 months to 36 months in Kenieba (30–10.3%) and Kita (60–6.6%) (Table 1 ). The main type of sleeping place was a bed at both sites at all sampling times (Table 1 ). The nets were mainly used by older children (> 13 years old) and adults in Kenieba at all times in both locations, except for the first year postdistribution, which was used by younger kids or kids/adults in Kita (Table 1 ). Table 1 Variables related to the use and handling of postdistribution campaign bednets in Mali, 2018–2020 Variable 12 months 24 months 36 months Kenieba/Yorkool N = 30 N = 30 N = 29 Location found hanging loose hanging folded/tied Not hanging 30.0% 36.6% 33.4% 16.6% 46.6% 36.6% 10.3% 34.4% 55.1% Type of sleeping place bed mattress mat/ground 63.3% 20.0% 3.3% 63.3% 0.0% 6.6% 72.4% 3.4% 10.3% Net users young child only young child + adult older child, adult only 26.6% 0.0% 73.3% 7.1% 28.5% 64.2% 0.0% 0.0% 100% Kita/PermaNet 2.0 N = 30 N = 30 N = 30 Location found hanging loose hanging folded/tied Not hanging 60.0% 30.0% 10.0% 70.0% 23.3% 6.6% 6.6% 56.6% 36.6% Type of sleeping place bed mattress mat/ground 86.6% 0.0% 0.0% 83.3% 10.0% 6.6% 73.3% 0.0% 26.6% Net users young child only young child + adult older child, adult only 50.0% 50.0% 0.0% 5.0% 20.0% 75.5% 8.3% 16.6% 75.0% The variables related to net use for the nets sampled throughout the time cohorts are shown in Table 2 . The proportion of nets used the previous night was lower in Kenieba (56.6–53.3%) than in Kita (93.3–90.0%) from 12 ( p = 0.0068) to 24 months (p = 0.0012) , but it was similar ( p = 0.0959 ) at both sites at 36 months (Table 2 ). The proportion of nets used the last week every night was also lower in Kenieba (56.6–27.5%) than in Kita (83.3–50%) at 12 months ( p = 0.008 ) and 24 months ( p = 0.0029 ) at 36 months ( p = 0.055 ) (Table 2 ). Overall, a greater proportion of ‘net use’ was observed in Kita throughout the study. Although the proportion of net ‘not use’ increased for both sites, the proportion of no use remained at 30% in Kita at the 36-month point but increased to 69% in Kenieba. Nets were used equally in the rainy and dry seasons at both sites (Table 2 ). Table 2 Variables related to the use of bioassay test nets, Mali, 2018–2020 Variable 12 months 24 months 36 months Kenieba/Yorkool N = 30 N = 30 N = 29 Used last night 56.6% 53.3% 31.0% Use last week every night most (5–6) some (1–4) not used do not know 56.6% 0.0% 6.6% 36.6% 0.0% 50.0% 10.0% 10.0% 30.0% 0.0% 27.5% 3.4% 0.0% 68.9% 0.0% Seasonal use equally rain and dry mainly rain rain only 53.3% 36.6% 10.0% 56.6% 10.0% 33.3% 44.8% 37.9% 17.2% Kita/PermaNet 2.0 N = 30 N = 30 N = 30 Used last night 90.0% 93.3% 53.3% Use last week every night most (5–6) some (1–4) not used do not know 83.3% 6.6% 6.6% 3.3% 0.0% 93.3% 0.0% 3.3% 3.3% 0.0% 50.0% 3.3% 6.6% 30.0% 10.0% Seasonal use equally rain and dry mainly rain rain only 73.3% 23.3% 3.3% 100.0% 0.0% 0.0% 86.6% 6.6% 6.6% The variables related to the washing of the sampled nets were also assessed. The proportion of nets washed was high (≥ 70%) at both sites at 12, 24 and 36 months (Table 3 ). The mean number of washes in the last six months (all/if washed) was approximately 3.0 at both sites at 12, 24 and 36 months. The main soap used was a local soap bar, detergent or bleach at both sites at 12, 24 and 36 months. Table 3 Variables Related to the Washing of Bioassay Test Nets, Mali, 2018–2020 Variable 12 months 24 months 36 months* Kenieba/Yorkool N = 30 N = 30 N = 29 Ever washed 70.0% 93.3% 79.3% Washes last 6 months (all) Mean Median 3.2 1 2.8 2 2.0 2 Washes last 6 months (if washed) Mean Median 4.5 2 3 2 2.6 2 Soap used country soap bar detergent or bleach mix 38.1% 52.3% 9.5% 32.1% 57.1% 10.7% 21.7% 43.4% 26.0% Kita/PermaNet 2.0 N = 30 N = 30 N = 30 Ever washed 83.3% 96.6% 93.3% Washes last 6 months (all) Mean Median 2.4 2 3.1 2 3.0 3 Washes last 6 months (if washed) Mean Median 2.9 2 3.2 2 3.2 3 Soap used country soap bar detergent or bleach mix 36.0% 64.0% 0.0% 37.9% 27.5% 34.4% 25.0% 50.0% 3.5% Insecticidal activity The results for the determination of insecticide bioefficacy for Yorkool nets collected in Kenieba nets and PermaNet 2.0 nets collected in Kita 6, 12, 24 and 36 months are shown in Table 4 . At each point in time, the proportion of nets with optimal effectiveness (at least 95% K.D. or 80% mortality) was 80% at 6, 12, and 24 months, but at 36 months, it decreased with both types of nets and at both sites (Table 4 ). The proportions of nets with optimal and minimal effectiveness were similar ( p > 0.05 ) for both types of nets during the 36-month survey (Table 4 ). Minimal effectiveness was acceptable at both sites until the 24-month assessment but decreased dramatically at 36 months to 51.7% and 60%, respectively, with Yorkool nets in Kenieba and PermaNet 2.0 in Kita (Table 4 ). Table 4 Cone bioassay results using a susceptible colony of An. coluzzii on Yorkool and PermaNet 2.0 ITNs, Mali, 2018–2020 Site/Net 6 months (Baseline) 12 months 24 months 36 months Kenieba/Yorkool N = 30 N = 30 N = 30 N = 29 KD60 Mean (95% CI) Median (IQR) 94.6% (90.5–98.6) 98% (94.0-99.7) 85.6% (78.2–93.5) 94% (82-99.7) 90.5% (83.5–97.5) 96% (96.0-100.0) 67.3% (55.2–79.5) 78.0% (38.0–96.0) Mortality 24 hours Mean (95% CI) Median (IQR) 54.4% (47.8–60.9) 54.0% (42.0–66.0) 74.1% (63.5–84.7) 79% (72-89.7) 54.2% (44.3–64.2) 57.0% (44.2–72.4) 42.4% (29.7–55.1) 36.0% (22.0–60.0) Optimal effectiveness Estimate (95% CI) 66.6% (45.8–82.5) 70.0% (47.9–85.5) 70.0% (47.9–85.5) 31.0% (15.1–53.1) Minimal effectiveness Estimate (95% CI) 96.6% (77.7–99.5) 100% 93.3% (75.8–98.4) 51.7%(32.7–70.1) Kita/PermaNet 2.0 N = 30 N = 30 N = 30 N = 30 KD60 Mean (95% CI) Median (IQR) 94.9% (92.8–96.9) 97.0% (94.0-100.0) 93.7% (89.4–98.1) 98% (94.2–100) 84.2% (76.5–91.8) 95% (78.0-99.7) 64.5% (53.7–75.3) 66.0% (42.0–94.0) Mortality 24 hours Mean (95% CI) Median (IQR) 62.0% (53.6–70.5) 59.0% (48.0–72.0) 71.2% (63.8–78.6) 69% (64.2–77.7) 65.2% (57.2–73.3) 62.0% (58.2–74.0) 39.8% (33.8–45.8) 40.0% (28.0–54.0) Optimal effectiveness Estimate (95% CI) 66.6% (53.1–77.8) 76.6% (48.9–91.8) 56.6% (37.0-74.3) 20.0% (8.0-41.5) Minimal effectiveness Estimate (95% CI) 100.0% 100% 96.6% (77.7–99.5) 60.0% (38.9–77.8) Insecticide surface level The mean surface concentrations of insecticide residue on ITNs collected at 6 (baseline), 12, 24 and 36 months and measured by C-Vue are presented in Table 5 . The surface concentration of insecticide residue was greater in Yorkool nets (0.69 mg/m 2 ) than in PermaNet 2.0 nets (0.46 mg/m 2 ) ( p = 0.0211) at 6 months, but it was approximately the same in Yorkool nets (0.20 mg/m 2 ) and in PermaNet 2.0 nets (0.24 mg/m 2 ) ( p = 0.1907) at 12 months. The estimated contents remained similar for both types of nets across the survey: Yorkool nets (0.19 mg/m 2 ) and PermaNet 2.0 nets (0.17 mg/m 2 ) ( p = 0.7901 ) at 24 months and at 36 months (0.08 and 0.06 mg/m 2 - Yorkool-PermaNet 2.0, respectively—p = 0.1808 ) (Fig. 3). By converting surface levels to total levels of deltamethrin, the mean concentration decreased from 55 mg/m 2 (100.0%) to 29 mg/m 2 (71.0%), 28 mg/m 2 (72.5%) and 14 mg/m 2 (88.6%) at 6, 12, 24 and 36 months, respectively, for Yorkool nets. It decreased from 55 mg/m 2 (100.0%) to 29 mg/m 2 (47.8%), 28 mg/m 2 (63.0%), and 14 mg/m 2 (87.0%) at 6, 12, 24 and 36 months, respectively, for the PermaNet 2.0 nets (Table 5 ). By the end of the survey (36 months after distribution), the mean concentrations of available insecticide residue represented 11% (Yorkool nets) and 13% (PermaNet 2.0 nets) of the baseline insecticide concentration. Figure 3. Surface insecticide concentrations of the ITNs in Mali, 2018–2020: (a) Kenieba/Yorkool and (b) Kita/PermaNet 2.0 Table 5 Chemical Content Results on Yorkool and PermaNet 2.0 ITNs, Mali, 2018–2020 Variable 6 months (Baseline) 12 months 24 months 36 months Kenieba/Yorkool N = 30 N = 30 N = 30 N = 29 Converted total levels of insecticide (mg/m 2 ) 55 29 28 14 % Decrease compared to baseline - 71.0% 72.5% 88.4% Kita/PermaNet 2.0 N = 30 N = 30 N = 30 N = 30 Converted total levels of insecticide (mg/m 2 ) 45 32 26 6 % Decrease compared to baseline - 47.8% 63.0% 87.0% Discussion This ITN durability study aimed to compare the use practices and insecticidal durability of two communities following their distribution through a mass campaign. The nets distributed were multifilament polyester-based ITNs treated with 75-denier deltamethrin (Yorkool) or 100-denier deltamethrin (PermaNet 2.0). To assess the influence of the net use environment and behavioral factors, this study was conducted in two health districts, Kenieba and Kita, located in the Kayes Region, which have similar malaria epidemiological, climatic, and socioecological profiles. Net use practices The locations where nets were found (Hanging loose, hanging folded/tied, and not hanging) were similar at 12 and 36 months. However, the location of the net was different at 24 months, with a greater proportion of net hanging loose in Kita than in Kenieba. The risk of net physical damage increases when hanging loose or not hanging after use. This risk was high at each survey time at both sites. The main type of sleeping place was a bed frame (bamboo sticks) at both sites at the 12-, 24- and 36-month surveys. A similar result was found with the Magnet and PermaNet 2.0 study in Ethiopia [ 14 ] and in the Democratic Republic of Congo with DawaPlus 2.0 and DuraNet study [ 15 ]. This type of sleeping place increases the risk of net physical damage because some holes that form in the ITN are mechanical (such as sharp materials and bed edges) [ 4 ]. In most instances, the primary users of nets were older children (> 13 years old) and adults. This was unexpected because the primary users of nets are young children only and young children and adults. Similar results were observed in a study on Olyset and PermaNet 2.0 in Tanzania [ 16 ]. The proportion of nets used last night was lower in Kenieba (where the nets were Yoorkol) than in Kita (where the nets were PermaNet 2.0) at 12 and 24 months but similar at 36 months. However, the net use decreased between 12 and 36 months at both sites. The same results were observed for the proportion of nets used in the last week. There was no evidence of seasonal variation in net use, with nets used equally in both sites during the rainy and dry seasons. The proportion of nets washed was high (> 70%) at both sites at 12, 24 and 36 months. The mean number of washes in the last six months (all/if washed) was moderate, at approximately 3.0 at both sites at 12, 24, and 36 months. Similar results were observed in the Democratic Republic of the Congo with DawaPlus 2.0 in the DuraNet study [ 15 ]. The main soap used was country soap bar, detergent, or bleach at both sites at 12, 24, and 36 months. One factor that could have contributed to the rapid decrease in insecticide use is the use of detergent or bleach [ 17 , 18 ]. Insecticidal effectiveness using the WHO Cone Based on the WHO [ 10 ] criteria at each survey, the proportion of Yorkool and PermaNet 2.0 nets with optimal effectiveness (at least 95% K.D. or 80% mortality) was 80% at 6, 12, and 24 months but decreased radically at 36 months, decreasing to 52% with Yorkool and 60% with PermaNet 2.0. The proportions of nets with optimal and minimal effectiveness were similar for both types of nets during the entire study period, despite the differences in handling and use patterns observed in the sampled sites. These results contrast with those of studies conducted in Ethiopia, where MAGNET and PermaNet 2.0 retained their optimal effectiveness for up to 24 months [ 14 , 19 ]. Likewise, in Tanzania, the insecticidal durability of PermaNet 2.0 was excellent, with mean 60-min knockdown rates greater than 95% in WHO cone bioassay tests at all time points and a moderate decline in mean 24-h mortality rates from 93% at 12 months to 72% at 33 months (Haji et al., 2020). In the Democratic Republic of the Congo, the insecticidal effectiveness of DuraNet remained high throughout the follow-up and exceeded 80% of the optimal effectiveness at the 31-month assessment [ 15 ]. Similar results have also been reported for DuraNet from northern Tanzania, where these nets still had 94% mortality in bioassays after 20 washes [ 20 ], and at two sites in Nigeria where there was 97% optimal effectiveness after 36 months [ 21 ]. The insecticidal performance of Royal Sentry and MAGNet in Mozambique was also good up to the 24-month follow-up but declined at 36 months when only 3% of the samples showed optimal effectiveness in Inhambane, 11% in Tete, and 29% in Nampula. However, 96% of ITNs still had minimal effectiveness at 36 months [ 22 ]. Based on the PMI [ 12 ] guidelines, if less than 80% of the nets meet the optimal effectiveness criteria, the PMI recommends checking whether at least 80% of the nets meet the minimal effectiveness criteria. This is not an official WHO-established threshold, but it can provide a good assessment of how badly the efficiency of the nets is failing. If more than 80% of ITNs meet the minimal effectiveness evaluation criteria (75% K.D. or 50% 24-hour mortality), then there is a potential problem with the bioefficacy of ITNs, and further investigation of likely causes should be performed. If less than 80% of nets meet minimal effectiveness evaluation criteria, then a significant problem with the bioefficacy of the nets is very likely, and urgent investigation related to the possible causes should be performed. This study revealed that potential causes could include the use of country soap, a detergent, or bleach. Insecticidal effectiveness using HPLC The HPLC C-VUE method [ 13 ] showed that the mean deltamethrin concentration in Yorkool and PermaNet 2.0 nets decreased significantly over the study period. This value was below the WHO specification (WHO, 2021). At the end of the survey (36 months after distribution), the mean concentrations of available insecticide residue represented 11% (Yorkool nets) and 13% (PermaNet 2.0 nets) of the baseline insecticide concentration. Similar results were found in Ethiopia with MAGNet and PermaNet 2.0 using the Collaborative International Pesticide Analytical Council (CIPAC) method 454/LN/M/3.2 [ 11 ]. After 24 and 36 months, the mean chemical concentrations of alphacypermethrin and deltamethrin were 23.86% and 24.64% of the baseline concentration, respectively [ 14 ]. In Mozambique, with MAGNet and Royal Sentry nets, chemical testing of 36-month samples following the CIPAC method 454/LN/M/3.2 (WHO, 2021) revealed that the alphacypermethrin concentrations were 81%, 42% and 32% of the target dose [ 22 ]. In Nigeria, with DawaPlus net, following the CIPAC method 454/LN/M/3.2(WHO, 2021), the chemical residue of deltamethrin after 12 months was 55% and 46% of the initial loading dose [ 21 ]. In Kenya, at the end of years 1, 2 and 3 of Olyset Plus net usage, the permethrin content decreased by 36%, 40% and 52%, respectively, and the PBO content markedly decreased by 66%, 81%, and 87%, respectively. The loss of permethrin in Olyset Net was 16% in year one and did not change much in years 2 and 3 (19% and 24%, respectively) [ 23 ]. Conclusion Yorkool and Permanent 2.0 nets did not meet the WHO criteria of optimal effectiveness for the bioefficacy of ITNs in this 3-year survey, which could have resulted from the rapid loss of deltamethrin, as users did not follow the manufacturer's recommendations to not wash nets with local soap, detergent or bleach. Better community education is therefore essential to ensure the appropriate use and care of nets in areas with ITN-based interventions to maximize the operational impact on the prevention, control, and elimination of malaria. Failure to preserve the efficacy of nets would have operational implications, requiring early replenishment with new nets to ensure that such an ITN-based malaria intervention remains effective. The C-Vue portable chromatographic device was used successfully for the first time in Mali to measure the surface-level insecticide concentration of ITNs. These results were consistent with those of cone bioassays. This new technology allows for an affordable and locally available, nondestructive method to monitor the insecticide content of ITN in malaria-endemic countries. List Of Abbreviations ITN Insecticide Treated Net PMI President Malaria Initiative WHO World Health Organization CIPAC Collaborative International Pesticide Analytical Council HPLC High-Performance Liquid Chromatography WHOPES World Health Organization Pesticide Evaluation Scheme KD Knock Down CE Comite Ethique INRSP Institut National de Recherche en Sante Publique SL Surface Level TL Total Level Declarations Ethical clearance The study protocol was translated into French and presented to the Mali National Institute of Public Health Research ethical committee for review. The clearance data were obtained on January 22, 2018, under reference number 02/2018/CE-INRSP. The staff implementing this study complied with all the policies and procedures of both the PMI and the local ethics board. Informed oral consent was obtained from all participants in this study prior to conducting the interviews. Consent for publication Not applicable. Availability of data and materials The datasets used and analyzed during the current study are available from the corresponding author upon reasonable request. Competing interests The authors declare that they have no competing interests. Funding This work was made possible by the support of the American people through the United States Agency for International Development (USAID) and the U.S. President's Malaria Initiative (PMI) under contract No: AID-OAA-I-17-00008. The contents do not necessarily reflect the views of USAID, PMI, or the United States Government. Authors' contributions Design of the study and tools: MBMC; I.T.; PM implementation and supervision: MBMC; I.T., MS, Y.D., A.D., JMS, S.S., A.D. and OK; bioassay: MBMC, I.T., MS, Y.D., A.D., JMS; and L.K.; chemical testing: MBMC; IT and Y.D., L.K.; analysis and interpretation: MBM, TSA; I.T and L.S., manuscript: all. Acknowledgments We want to thank all the staff involved in this study and support it at the international, national, regional, and community levels. Special thanks go to the chief medical officer of the Kenieba and Kita health districts and VectorLink Mali staff. References Lengeler C (2000) Insecticide-treated bednets and curtains for preventing malaria. Cochrane Database Syst Rev. ;(2):CD000363 Randriamaherijaona S, Briët OJT, Boyer S, Bouraima A, N’Guessan R, Rogier C et al (2015) Do holes in long-lasting insecticidal nets compromise their efficacy against pyrethroid resistant Anopheles gambiae and Culex quinquefasciatus? Results from a release-recapture study in experimental huts. Malar J. 28 août. ;14:332 WHO Guidelines for monitoring the durability of long-lasting insecticidal mosquito nets under operational conditions [Internet]. 2011 [cité 15 mars 2024]. Disponible sur: https://www.who.int/publications-detail-redirect/9789241501705 WHO (2015) Stratégie technique mondiale de lutte contre le paludisme 2016–2030 [Internet]. Genève: Organisation mondiale de la Santé; [cité 15 mars 2024]. 33 p. Disponible sur: https://iris.who.int/handle/10665/176720 PMI (2023) U.S. President’s Malaria Initiative - Mali PMI (2013) President’s Malaria Initiative: Mali Malaria Operational Plan FY 2015 INSTAT (2018) Mali Demographic and Health Surveys. Bamako, Mali et Rockville Maryland, USA African IRS, Project (2017) p Impact of New Combination LLIN Products on Entomological Measures of Malaria Transmission in Southern Mali. Bethesda, MD, USA; WHO (2013) WHO Guidance Note for Estimating the Longevity of Long-Lasting Insecticidal Nets in Malaria Control September 2013 WHO (2013) Guidelines for laboratory and field-testing of long-lasting insecticidal nets [Internet]. [cité 15 mars 2024]. Disponible sur: https://www.who.int/publications-detail-redirect/WHO-HTM-NTD-WHOPES-2013.1 WHO. WHO SPECIFICATIONS AND EVALUATIONS FOR PUBLIC HEALTH PESTICIDES, (2021) DELTAMETHRIN LONG-LASTING (INCORPORATED INTO FILAMENTS) INSECTICIDAL NET PMI (2017) LLIN Durability Monitoring | Toolkit and Data Repository for PMI-funded LLIN durability monitoring studies [Internet]. [cité 15 mars 2024]. Disponible sur: https://www.durabilitymonitoring.org/ Traore I, Cisse M, Sow M, Swamidoss I, Dansoko Y, Dembele A et al (2014) Evaluation of a Portable, Field-adapted, Spring-driven Chromatographic Device and Sampling Technique for Rapid Measurement of Deltamethrin Surface Levels on Insecticide-treated Nets Hiruy HN, Irish SR, Abdelmenan S, Wuletaw Y, Zewde A, Woyessa A et al Durability of long-lasting insecticidal nets (LLINs) in Ethiopia. Malar J [Internet]. 26 mars 2023 [cité 18 oct 2023];22(1):109. Disponible sur: https://doi.org/10.1186/s12936-023-04540-3 Mansiangi P, Umesumbu S, Etewa I, Zandibeni J, Bafwa N, Blaufuss S et al (2020) Comparing the durability of the long-lasting insecticidal nets DawaPlus® 2.0 and DuraNet© in northwest Democratic Republic of Congo. Malar J. 24 mai. ;19(1):189 Haji KA, Khatib BO, Obi E, Dimoso K, Koenker H, Babalola S et al (2020) Monitoring the durability of the long-lasting insecticidal nets Olyset® and PermaNet® 2.0 in similar use environments in Zanzibar. Malar J. 24 mai. ;19(1):187 Atieli FK, Munga SO, Ofulla AV, Vulule JM (2010) Wash durability and optimal drying regimen of four brands of long-lasting insecticide-treated nets after repeated washing under tropical conditions. Malar J 30 août 9:248 Kayedi MH, Lines JD, Haghdoost AA, Vatandoost MH, Rassi Y, Khamisabady K (2008) Evaluation of the effects of repeated hand washing, sunlight, smoke and dirt on the persistence of deltamethrin on insecticide-treated nets. Trans R Soc Trop Med Hyg août 102(8):811–816 Solomon T, Loha E, Deressa W, Balkew M, Gari T, Overgaard HJ et al (2018) Bed nets used to protect against malaria do not last long in a semi-arid area of Ethiopia: a cohort study. Malar J. 20 juin. ;17(1):239 Mahande AM, Msangi S, Lyaruu LJ, Kweka EJ (2018) Bio-efficacy of DuraNet® long-lasting insecticidal nets against wild populations of Anopheles arabiensis in experimental huts. Trop Med Health 46:36 E O FO, Oo SBBOJA O, Monitoring the physical and insecticidal durability of the long-lasting insecticidal net DawaPlus® 2.0 in three States in Nigeria. Malar J [Internet]. 30 mars 2020 [cité 15 mars 2024];19(1). Disponible sur: https://pubmed.ncbi.nlm.nih.gov/32228592/ Abílio AP, Obi E, Koenker H, Babalola S, Saifodine A, Zulliger R et al (2020) Monitoring the durability of the long-lasting insecticidal nets MAGNet and Royal Sentry in three ecological zones of Mozambique. Malar J. 17 juin. ;19(1):209 Gichuki PM, Kamau L, Njagi K, Karoki S, Muigai N, Matoke-Muhia D et al (2021) Bioefficacy and durability of Olyset® Plus, a permethrin and piperonyl butoxide-treated insecticidal net in a 3-year long trial in Kenya. Infect Dis Poverty. 20 déc. ;10(1):135 Additional Declarations The authors declare no competing interests. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4749503","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":327711618,"identity":"d8111bb5-bdc1-46aa-b470-60c3615e8c02","order_by":0,"name":"Moussa BM Cisse","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA7ElEQVRIiWNgGAWjYDADNhDxoeAAmCMBxDJEaWGcYYDQwkOUTcw8xGjRbe8x/vijhkGej//4w8c2Bnei+RuYD97mYdiGU4vZmTNm0jzHGAzbJHKMjXMMnuXOOMCWbM3DcBu3lhs5ZsxAjySwSfCwSecYHM5tOMADNAS/FqDD/gG18B9//tsCqGX+Af5vhLQYSPC2AbUwJACtA2rZcABoHV4tZ46VSfP2SYD9ItkD9MvGw2zGlnMM8Gg53rz5449vNvLy/ccffvhRcSd33vHmhzfeVNyWw6UFCiSQ2MwgwoCAhlEwCkbBKBgFeAEAAjpQj5U7lN4AAAAASUVORK5CYII=","orcid":"","institution":"USAID PMI ITN durability monitoring project, Bamako-Mali/ Laboratoire de Biologie Moléculaire Appliquée, Université des Sciences, Techniques et Technologies de Bamako, Bamako-Mali","correspondingAuthor":true,"prefix":"","firstName":"Moussa","middleName":"BM","lastName":"Cisse","suffix":""},{"id":327711619,"identity":"ca760f58-23cd-4d0c-9085-4b8219c494ab","order_by":1,"name":"Ibrahim Troare","email":"","orcid":"","institution":"USAID PMI ITN durability monitoring project, Bamako-Mali/ Laboratoire de Biologie Moléculaire Appliquée, Université des Sciences, Techniques et Technologies de Bamako, Bamako-Mali","correspondingAuthor":false,"prefix":"","firstName":"Ibrahim","middleName":"","lastName":"Troare","suffix":""},{"id":327711620,"identity":"24fdbd02-942d-40f5-a944-2418751abcac","order_by":2,"name":"Mamadou Sow","email":"","orcid":"","institution":"Laboratoire de Biologie Moléculaire Appliquée, Université des Sciences, Techniques et Technologies de Bamako, Bamako-Mali","correspondingAuthor":false,"prefix":"","firstName":"Mamadou","middleName":"","lastName":"Sow","suffix":""},{"id":327712549,"identity":"8b482fd5-cdb7-4aa3-bc85-a43058d446d9","order_by":3,"name":"Yacouba Dansoko","email":"","orcid":"","institution":"USAID PMI ITN durability monitoring project, Bamako-Mali/ Laboratoire de Biologie Moléculaire Appliquée, Université des Sciences, Techniques et Technologies de Bamako, Bamako-Mali","correspondingAuthor":false,"prefix":"","firstName":"Yacouba","middleName":"","lastName":"Dansoko","suffix":""},{"id":327712550,"identity":"70a4a5d0-d68d-4cd1-8da1-7f3e38e80dcb","order_by":4,"name":"Alice Dembele","email":"","orcid":"","institution":"USAID PMI ITN durability monitoring project, Bamako-Mali/ Laboratoire de Biologie Moléculaire Appliquée, Université des Sciences, Techniques et Technologies de Bamako, Bamako-Mali","correspondingAuthor":false,"prefix":"","firstName":"Alice","middleName":"","lastName":"Dembele","suffix":""},{"id":327712551,"identity":"3a964978-115e-4490-b0eb-d00c83e94d39","order_by":5,"name":"Lazeni Konate","email":"","orcid":"","institution":"Laboratoire de Biologie Moléculaire Appliquée, Université des Sciences, Techniques et Technologies de Bamako, Bamako-Mali","correspondingAuthor":false,"prefix":"","firstName":"Lazeni","middleName":"","lastName":"Konate","suffix":""},{"id":327714252,"identity":"efd21b8d-f7dc-40cf-b5ed-80f05177b6b0","order_by":6,"name":"Jean Marie Sanou","email":"","orcid":"","institution":"USAID PMI ITN durability monitoring project, Bamako-Mali/ Laboratoire de Biologie Moléculaire Appliquée, Université des Sciences, Techniques et Technologies de Bamako, Bamako-Mali","correspondingAuthor":false,"prefix":"","firstName":"Jean","middleName":"Marie","lastName":"Sanou","suffix":""},{"id":327714253,"identity":"fb47dd04-eeec-46c1-9c95-4f26aa4ebea0","order_by":7,"name":"Youssouf Diarra","email":"","orcid":"","institution":"Laboratoire de Biologie Moléculaire Appliquée, Université des Sciences, Techniques et Technologies de Bamako, Bamako-Mali","correspondingAuthor":false,"prefix":"","firstName":"Youssouf","middleName":"","lastName":"Diarra","suffix":""},{"id":327714254,"identity":"7bd279a1-651e-418c-86c8-56922746a103","order_by":8,"name":"Samah Sissoko","email":"","orcid":"","institution":"Programme National de Lutte contre le Paludisme, Bamako-Mali","correspondingAuthor":false,"prefix":"","firstName":"Samah","middleName":"","lastName":"Sissoko","suffix":""},{"id":327714255,"identity":"3bb711c1-157f-4c5f-944a-a9a625f4453f","order_by":9,"name":"Abdourhamane Dicko","email":"","orcid":"","institution":"Programme National de Lutte contre le Paludisme, Bamako-Mali","correspondingAuthor":false,"prefix":"","firstName":"Abdourhamane","middleName":"","lastName":"Dicko","suffix":""},{"id":327714256,"identity":"ac132f7f-18fe-49e6-9600-35e78e0d5de8","order_by":10,"name":"Mahamadou Magassa","email":"","orcid":"","institution":"Programme National de Lutte contre le Paludisme, Bamako-Mali","correspondingAuthor":false,"prefix":"","firstName":"Mahamadou","middleName":"","lastName":"Magassa","suffix":""},{"id":327743738,"identity":"34ef8950-9c20-4181-b798-87d7e7745159","order_by":11,"name":"Lansana Sangare","email":"","orcid":"","institution":"President's Malaria Initiative, U.S. Agency for International Development, Bamako, Mali","correspondingAuthor":false,"prefix":"","firstName":"Lansana","middleName":"","lastName":"Sangare","suffix":""},{"id":327743739,"identity":"37deacf4-c5b9-4f89-ba2c-4c91373424ea","order_by":12,"name":"Celestin Kouambeng","email":"","orcid":"","institution":"President's Malaria Initiative, U.S. Agency for International Development, Bamako, Mali","correspondingAuthor":false,"prefix":"","firstName":"Celestin","middleName":"","lastName":"Kouambeng","suffix":""},{"id":327743740,"identity":"08547815-15ef-401d-a170-371da5a217f8","order_by":13,"name":"Jules Mihigo","email":"","orcid":"","institution":"President's Malaria Initiative, U.S. Agency for International Development, Bamako, Mali","correspondingAuthor":false,"prefix":"","firstName":"Jules","middleName":"","lastName":"Mihigo","suffix":""},{"id":327743741,"identity":"180a1402-463c-4485-b2db-ba2b3a1b578d","order_by":14,"name":"Phillipe Mutwa","email":"","orcid":"","institution":"President's Malaria Initiative, U.S. Agency for International Development, Bamako, Mali","correspondingAuthor":false,"prefix":"","firstName":"Phillipe","middleName":"","lastName":"Mutwa","suffix":""},{"id":327743742,"identity":"fa4a446a-3e19-42e7-8c00-45c21bc7b5bf","order_by":15,"name":"Taiwo Samson Awolola","email":"","orcid":"","institution":"PMI/USAID, Washington, DC, USA /Entomology Branch, US Centers for Disease Control and Prevention, Atlanta, GA, USA.","correspondingAuthor":false,"prefix":"","firstName":"Taiwo","middleName":"Samson","lastName":"Awolola","suffix":""},{"id":327743743,"identity":"a43d230a-aab6-40ec-8688-392ac74e738c","order_by":16,"name":"Paula Marcet","email":"","orcid":"","institution":"PMI/USAID, Washington, DC, USA /Entomology Branch, US Centers for Disease Control and Prevention, Atlanta, GA, USA.","correspondingAuthor":false,"prefix":"","firstName":"Paula","middleName":"","lastName":"Marcet","suffix":""},{"id":327743744,"identity":"8cc9a2e5-cc1a-4c4c-a9c7-f9534e61e900","order_by":17,"name":"Ousmane Koita","email":"","orcid":"","institution":"USAID PMI ITN durability monitoring project, Bamako-Mali/ Laboratoire de Biologie Moléculaire Appliquée, Université des Sciences, Techniques et Technologies de Bamako, Bamako-Mali","correspondingAuthor":false,"prefix":"","firstName":"Ousmane","middleName":"","lastName":"Koita","suffix":""}],"badges":[],"createdAt":"2024-07-16 11:56:06","currentVersionCode":1,"declarations":{"humanSubjects":true,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":true,"humanSubjectConsent":true,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-4749503/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4749503/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":60564029,"identity":"1a579823-d66f-4ea3-9146-602e2ee0b4b1","added_by":"auto","created_at":"2024-07-18 08:10:29","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":151944,"visible":true,"origin":"","legend":"\u003cp\u003eNet collection sites in Mali, 2018-2020\u003c/p\u003e","description":"","filename":"Figure1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4749503/v1/793f0c70e43dc79ba64008b7.jpg"},{"id":60564041,"identity":"d0d9e4f5-8b48-486b-89bb-d56be1f1d99a","added_by":"auto","created_at":"2024-07-18 08:10:35","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":35042,"visible":true,"origin":"","legend":"\u003cp\u003eStudy design from 2017 to 2020\u003c/p\u003e","description":"","filename":"Figure2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4749503/v1/fc22b0ec081810b8e5cd722b.jpg"},{"id":60564040,"identity":"d88eaa47-2429-46fb-8410-c3c40220b1f2","added_by":"auto","created_at":"2024-07-18 08:10:34","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":38222,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSurface insecticide concentrations of the ITNs in Mali, 2018-2020, (a) Kenieba/Yorkool and (b) Kita/PermaNet 2.0\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"Figure3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4749503/v1/6b57a2a8ab25b96ab07c50bf.jpg"},{"id":60564051,"identity":"864a0e61-3cf4-4de0-81f8-79904463712a","added_by":"auto","created_at":"2024-07-18 08:10:41","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1121837,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4749503/v1/67083d27-e751-4c11-9985-f6fff309e316.pdf"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003eUse of a portable field-adapted liquid chromatographic system (C-Vue machine) to estimate the quantity of deltamethrin on insecticide-treated nets paired with WHO cone bioassays to determine ITN bioefficacy as part of three-year durability monitoring in Mali\u003c/p\u003e","fulltext":[{"header":"Background","content":"\u003cp\u003eInsecticide-treated nets (ITNs) play a significant role in preventing and controlling vector-borne diseases, especially malaria. They provide personal protection and can reduce transmission and protect an entire community (i.e., a mass effect) in settings with sustained high levels of coverage and anthropophilic vectors [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. ITNs provide both a physical barrier and repellent protection through insecticides. For malaria control with ITNs, the World Health Organization (WHO) currently recommends universal coverage of one ITN for every two people in a household [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. In many current ITN distribution programs, it is assumed that ITNs have a relatively uniform lifespan of approximately 3 years. Thus, it is often assumed that mass distribution campaigns at 3-year intervals are sufficient to maintain adequate net coverage levels throughout the 3-year interval [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Distributing additional nets through routine immunization programs or prenatal services is also recommended. However, recent longitudinal studies and surveys have revealed that this assumption of a uniform 3-year lifespan may be overly optimistic and that the rate at which net coverage declines after a campaign may be substantially more variable and more rapid than previously assumed. Therefore, the WHO now recommends that the delivery of ITNs through immunization and antenatal services be given as much priority as delivery through periodic campaigns [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eITNs are a key component of the malaria vector control strategy in Mali, where donors such as the U.S. President's Malaria Initiative (PMI) and Global Fund (G.F.) have distributed millions of nets since program implementation began in 2007 [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. ITN distribution strategies in Mali are based on providing access through mass distribution campaigns to the entire target population at a rate of 2 people per net, as well as routine distribution to pregnant women and children under one year of age during prenatal consultations for women and the Expanded Program on Immunization for Children [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. These strategies are reinforced by educational communication encouraging net care and use at the community level. Mali began with the ITN mass distribution campaign in 2011. Due to the difficulties in mobilizing the resources to cover all countries in one campaign in 2011, the National Malaria Control Program (NMCP) organized a region-by-region mass campaign distribution according to the national strategic plan. The NMCP organized at least one campaign in each region and Bamako District from 2011 to 2018 [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e], and an interval of 3 years was established between campaigns in each region. Progress has been particularly impressive in increasing ITN coverage, as 90% of households in Mali have at least one ITN, and 55% of households have one ITN for two persons [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. The first ITN durability monitoring in Mali was undertaken from 2014 to 2016 with four types of ITNs (PermaNet 2.0, PermaNet 3.0, Olyset Net, and OlysetPlus Net) in two districts: S\u0026eacute;lingu\u0026eacute; and Bougouni, which are located in the southern Mali region of Sikasso. Among the results of that study, the proportionate hole index 36 months after the net distribution was much lower in PermaNet 2.0 and PermaNet 3.0 than in Olyset Net and OlysetPlus Net [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eMali\u0026rsquo;s NMCP planning for long-term coverage with ITNs requires information on the durability of different ITN products in local settings to choose which products to procure and to determine whether particular products are likely to perform best over time in a given setting. This also informs the necessary rate of replacement in continuous distribution systems, the appropriate interval between campaigns and, when necessary, plans for disposal or recycling of old nets. Monitoring the durability of nets may lead to a better understanding of the factors that determine ITN durability and the laboratory indicators that correlate with these net qualities. It can also provide an opportunity to improve behavior and communication messages so that users can take better care of their ITNs [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe WHO and Vector Control Technical Expert Group (VCTEG) guidelines describe methods for assessing ITN durability based on net attrition, insecticide content, insecticidal activity, and physical integrity [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Insecticide levels on ITNs are typically analyzed using a straight-phase high-performance liquid chromatography (HPLC) technique recommended by the Collaborative International Pesticides Analytical Council (CIPAC). The expense of the instrument and the reagents required for the analysis precludes many malaria-endemic resource-limited countries from carrying out proper monitoring of deltamethrin levels. Therefore, there is a need to develop a method that uses a portable and inexpensive liquid chromatographic device along with a nondestructive sampling technique to measure deltamethrin levels on deltamethrin-coated polyester nets.\u003c/p\u003e \u003cp\u003eThe importance of physical and insecticidal net durability is recognized as a critical factor, and a malaria control program needs to know how to determine the frequency at which nets should be replaced and the type of nets to be procured. This study assessed the insecticidal (bioefficacy and insecticide content) durability of ITNs (Yorkool and PermaNet 2.0) in two villages at 6, 12, 24, and 36 months after a net mass distribution was carried out in December 2017. The objectives of this study were to 1) determine the net use and washing practices within the communities, 2) assess the insecticidal effectiveness using the WHO cone bioassays test method, and 3) estimate the insecticidal content using the C-Vue HPLC method.\u003c/p\u003e"},{"header":"Method","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy sites and period\u003c/h2\u003e \u003cp\u003eThe ITN mass campaign in the Kayes Region was conducted in December 2017, and data collection was conducted between March and May 2018 at an average of 6 months postdistribution as a baseline, at 12 months (December 2018), 24 months (November-December 2019) and 36 months (November-December 2020). The study was carried out in the districts of Kenieba and Kita, located in the Kayes Region, at sites with similar malaria epidemiological, climatic and socioecological profiles. For the selection of clusters, the campaign ITN distribution registries were used at both sites. A cluster was defined as a community, and the selection was performed with probability proportionate to size, with the number of ITNs distributed per community as the measure of size. In each of the districts, 15 clusters (village) were selected, and a grape (group of 5 households) was selected in each (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eITN Brands\u003c/h2\u003e \u003cp\u003eYorkool nets were monitored in Kenieba, and PermaNet 2.0 nets were monitored in Kita, as those were the brands procured and distributed in each region. The technical specifications of the ITNs (material, textile specific, insecticide with concentration) are the same for the two brands, except that Yorkool nets are 75-denier and PermaNet 2.0 is 100-denier (a measure of fabric thickness). Both nets are made of knitted polyfilament polyester fibers and are treated with deltamethrin to a target concentration of 55 mg/m2 (WHO, 2021).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eStudy Design\u003c/h2\u003e \u003cp\u003eThis study is a part of the ITN durability monitoring project [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e], and it is a prospective longitudinal study of a cohort of nets distributed in December 2017 as part of a mass distribution campaign. Sampling was carried out in 15 clusters (from villages) per study site (Heath District), and each cluster contained 1 grape (5 households). Within a few months following distribution (from March to May 2018), a household survey was carried out at each study site to identify representative households that received campaign nets and request that owners consent to participate in the study. Campaign nets from consenting households were selected to constitute the cohorts of nets for the three-year study period. These nets were labeled with a unique code at baseline (within 6 months postdistribution). At each period (baseline, 12, 24, and 36 months) (Fig.\u0026nbsp;2), 30 campaign nets per site (Health District) were selected for insecticide effectiveness testing (bioassays and chemical residue).\u003c/p\u003e \u003cp\u003eFigure 2. Study design from 2017 to 2020\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eNets Sampling\u003c/h2\u003e \u003cp\u003eAt baseline, a cohort of ten (15) nets per cluster was tagged for eventual follow-up and removal at the 12-24- and 36-month assessments. Using a separate group of two-digit tags (A1-A6, B1-B6, etc.), households were selected randomly at baseline. One net in each of these households was tagged for follow-up at 6, 12, and 24 months, and the GPS location of the household was recorded. Following the WHO recommendation for phase III testing of ITNs (WHO, 2013b), random samples of 30 campaign nets per site (a total of 60) were selected at each annual assessment. Households were given a new ITN as a replacement. The collected nets were labeled and stored in separate plastic bags for transportation.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eDetermination of net use and washing practices within communities\u003c/h2\u003e \u003cp\u003eFollowing the WHO [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] and U.S. President Malaria Initiative [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] guidelines, a one-page questionnaire confirming that the net was received during the campaign and obtaining basic information on net use, storage and washing patterns was administered to each participating household at the 6-month (baseline), 12-month, 24-month and 36-month assessments. Electronic data captured using Samsung Galaxy Tab A devices with ODK questionnaires were used to allow detailed programming of skip patterns and internal controls to ensure that the necessary data were consistent and complete.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eDetermination of insecticidal effectiveness using the WHO Cone\u003c/h2\u003e \u003cp\u003eFollowing WHO guidelines [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e], the insecticidal activity (biological efficacy) of the ITNs was determined with WHO cone tests using the susceptible mosquito \u003cem\u003eAnopheles coluzzii\u003c/em\u003e Ngousso reared in a local insectary at LBMA. For each assessment period, 6-, 12-, 24- and 36-month bioassays were conducted with five pieces of netting measuring 25 \u0026times; 25 cm, with 10 mosquitoes exposed on each piece of netting (total\u0026thinsp;=\u0026thinsp;50 mosquitoes per net). Mortality and knockdown (KD) rates were used to evaluate the bioefficacy of the nets.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eDetermination of insecticidal content using HPLC\u003c/h2\u003e \u003cp\u003eThe same pieces of nets from the 6-, 12-, 24- and 36-month assessments of insecticidal activity were used for the determination of insecticide surface levels with the portable HPLC C-Vue (C-Vue\u0026reg; Portable Liquid Chromatograph Model CH2B) following the method described by [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Briefly, values generated by C-Vue chromatography are surface levels (S.L.) of deltamethrin obtained by rubbing the net with filter paper, which is nondestructive to the nets, and analyzing the residue through liquid chromatography. This method allows us to estimate the mean and median levels of active ingredients (insecticides) in mg/m2 across the net samples. These values are later compared with manufacturer specifications for the insecticide content of each net brand. A conversion equation was used to estimate the total level (T.L.) of insecticide from the mean surface level (S.L.): T.L. = (Log(SL)\u0026thinsp;+\u0026thinsp;1.37)/0.0232). This equation was obtained through laboratory replication and 2 independent C-values and validated with gold standard HPLC [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003eData analysis\u003c/h2\u003e \u003cp\u003eOnce data collection for 6-, 12-, 24-, and 36-month rounds were completed and the data were verified, the data were transferred to a statistical software package (STATA for Windows, Version 14.0) for further consistency checks and preparation for analysis. The data analysis was conducted by using Stata do files (macros). \u003cem\u003eThe chi-square\u003c/em\u003e test was used for the comparison of proportions and mean values between the two sites. According to the World Health Organization Pesticide Evaluation Scheme (WHOPES) Phase III evaluation criteria, at least 80% of recommended ITN brands should achieve optimal effectiveness 36 months postdistribution. The following criteria were used to determine the optimal effectiveness of the nets: KD 60 mn\u0026thinsp;\u0026ge;\u0026thinsp;95% or mortality\u0026thinsp;\u0026ge;\u0026thinsp;80% and minimal effectiveness: KD60 mn\u0026thinsp;\u0026ge;\u0026thinsp;75% or mortality\u0026thinsp;\u0026ge;\u0026thinsp;50%. The surface level and the total level of insecticides from each assessment period were compared by using a t test.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eNet use practices\u003c/h2\u003e \u003cp\u003eThe patter nets of users, storage place, type of sleeping place, and type of washing are among the critical factors that contribute to physical deterioration of bednets.\u003c/p\u003e \u003cp\u003eThe locations of nets (hanging loose and folded/tied and not hanging) were the same at both sites (\u0026gt;\u0026thinsp;20.0%) at 12 months (\u003cem\u003ep\u0026thinsp;=\u0026thinsp;0.0660\u003c/em\u003e) and 36 months (\u003cem\u003ep\u0026thinsp;=\u0026thinsp;0.2136\u003c/em\u003e) but differed between Kenieba and Kita (\u003cem\u003ep\u0026thinsp;=\u0026thinsp;0.0012\u003c/em\u003e) at 24 months (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The proportion of net hanging loose decreased from 12 months to 36 months in Kenieba (30\u0026ndash;10.3%) and Kita (60\u0026ndash;6.6%) (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The main type of sleeping place was a bed at both sites at all sampling times (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The nets were mainly used by older children (\u0026gt;\u0026thinsp;13 years old) and adults in Kenieba at all times in both locations, except for the first year postdistribution, which was used by younger kids or kids/adults in Kita (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eVariables related to the use and handling of postdistribution campaign bednets in Mali, 2018\u0026ndash;2020\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12 months\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e24 months\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e36 months\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKenieba/Yorkool\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;29\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLocation found\u003c/p\u003e \u003cp\u003ehanging loose\u003c/p\u003e \u003cp\u003ehanging folded/tied\u003c/p\u003e \u003cp\u003eNot hanging\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e30.0%\u003c/p\u003e \u003cp\u003e36.6%\u003c/p\u003e \u003cp\u003e33.4%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e16.6%\u003c/p\u003e \u003cp\u003e46.6%\u003c/p\u003e \u003cp\u003e36.6%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10.3%\u003c/p\u003e \u003cp\u003e34.4%\u003c/p\u003e \u003cp\u003e55.1%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eType of sleeping place\u003c/p\u003e \u003cp\u003ebed\u003c/p\u003e \u003cp\u003emattress\u003c/p\u003e \u003cp\u003emat/ground\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e63.3%\u003c/p\u003e \u003cp\u003e20.0%\u003c/p\u003e \u003cp\u003e3.3%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e63.3%\u003c/p\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003cp\u003e6.6%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e72.4%\u003c/p\u003e \u003cp\u003e3.4%\u003c/p\u003e \u003cp\u003e10.3%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNet users\u003c/p\u003e \u003cp\u003eyoung child only\u003c/p\u003e \u003cp\u003eyoung child\u0026thinsp;+\u0026thinsp;adult\u003c/p\u003e \u003cp\u003eolder child, adult only\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e26.6%\u003c/p\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003cp\u003e73.3%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.1%\u003c/p\u003e \u003cp\u003e28.5%\u003c/p\u003e \u003cp\u003e64.2%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003cp\u003e100%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKita/PermaNet 2.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLocation found\u003c/p\u003e \u003cp\u003ehanging loose\u003c/p\u003e \u003cp\u003ehanging folded/tied\u003c/p\u003e \u003cp\u003eNot hanging\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e60.0%\u003c/p\u003e \u003cp\u003e30.0%\u003c/p\u003e \u003cp\u003e10.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e70.0%\u003c/p\u003e \u003cp\u003e23.3%\u003c/p\u003e \u003cp\u003e6.6%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e6.6%\u003c/p\u003e \u003cp\u003e56.6%\u003c/p\u003e \u003cp\u003e36.6%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eType of sleeping place\u003c/p\u003e \u003cp\u003ebed\u003c/p\u003e \u003cp\u003emattress\u003c/p\u003e \u003cp\u003emat/ground\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e86.6%\u003c/p\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e83.3%\u003c/p\u003e \u003cp\u003e10.0%\u003c/p\u003e \u003cp\u003e6.6%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e73.3%\u003c/p\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003cp\u003e26.6%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNet users\u003c/p\u003e \u003cp\u003eyoung child only\u003c/p\u003e \u003cp\u003eyoung child\u0026thinsp;+\u0026thinsp;adult\u003c/p\u003e \u003cp\u003eolder child, adult only\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e50.0%\u003c/p\u003e \u003cp\u003e50.0%\u003c/p\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.0%\u003c/p\u003e \u003cp\u003e20.0%\u003c/p\u003e \u003cp\u003e75.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e8.3%\u003c/p\u003e \u003cp\u003e16.6%\u003c/p\u003e \u003cp\u003e75.0%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe variables related to net use for the nets sampled throughout the time cohorts are shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The proportion of nets used the previous night was lower in Kenieba (56.6\u0026ndash;53.3%) than in Kita (93.3\u0026ndash;90.0%) from 12 (\u003cem\u003ep\u0026thinsp;=\u0026thinsp;0.0068)\u003c/em\u003e to 24 months \u003cem\u003e(p\u0026thinsp;=\u0026thinsp;0.0012)\u003c/em\u003e, but it was similar (\u003cem\u003ep\u0026thinsp;=\u0026thinsp;0.0959\u003c/em\u003e) at both sites at 36 months (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe proportion of nets used the last week every night was also lower in Kenieba (56.6\u0026ndash;27.5%) than in Kita (83.3\u0026ndash;50%) at 12 months (\u003cem\u003ep\u0026thinsp;=\u0026thinsp;0.008\u003c/em\u003e) and 24 months (\u003cem\u003ep\u0026thinsp;=\u0026thinsp;0.0029\u003c/em\u003e) at 36 months (\u003cem\u003ep\u0026thinsp;=\u0026thinsp;0.055\u003c/em\u003e) (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Overall, a greater proportion of \u0026lsquo;net use\u0026rsquo; was observed in Kita throughout the study. Although the proportion of net \u0026lsquo;not use\u0026rsquo; increased for both sites, the proportion of no use remained at 30% in Kita at the 36-month point but increased to 69% in Kenieba. Nets were used equally in the rainy and dry seasons at both sites (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eVariables related to the use of bioassay test nets, Mali, 2018\u0026ndash;2020\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12 months\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e24 months\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e36 months\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKenieba/Yorkool\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;29\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUsed last night\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e56.6%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e53.3%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e31.0%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUse last week\u003c/p\u003e \u003cp\u003eevery night\u003c/p\u003e \u003cp\u003emost (5\u0026ndash;6)\u003c/p\u003e \u003cp\u003esome (1\u0026ndash;4)\u003c/p\u003e \u003cp\u003enot used\u003c/p\u003e \u003cp\u003edo not know\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e56.6%\u003c/p\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003cp\u003e6.6%\u003c/p\u003e \u003cp\u003e36.6%\u003c/p\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e50.0%\u003c/p\u003e \u003cp\u003e10.0%\u003c/p\u003e \u003cp\u003e10.0%\u003c/p\u003e \u003cp\u003e30.0%\u003c/p\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e27.5%\u003c/p\u003e \u003cp\u003e3.4%\u003c/p\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003cp\u003e68.9%\u003c/p\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSeasonal use\u003c/p\u003e \u003cp\u003eequally rain and dry\u003c/p\u003e \u003cp\u003emainly rain\u003c/p\u003e \u003cp\u003erain only\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e53.3%\u003c/p\u003e \u003cp\u003e36.6%\u003c/p\u003e \u003cp\u003e10.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e56.6%\u003c/p\u003e \u003cp\u003e10.0%\u003c/p\u003e \u003cp\u003e33.3%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e44.8%\u003c/p\u003e \u003cp\u003e37.9%\u003c/p\u003e \u003cp\u003e17.2%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKita/PermaNet 2.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUsed last night\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e90.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e93.3%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e53.3%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUse last week\u003c/p\u003e \u003cp\u003eevery night\u003c/p\u003e \u003cp\u003emost (5\u0026ndash;6)\u003c/p\u003e \u003cp\u003esome (1\u0026ndash;4)\u003c/p\u003e \u003cp\u003enot used\u003c/p\u003e \u003cp\u003edo not know\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e83.3%\u003c/p\u003e \u003cp\u003e6.6%\u003c/p\u003e \u003cp\u003e6.6%\u003c/p\u003e \u003cp\u003e3.3%\u003c/p\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e93.3%\u003c/p\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003cp\u003e3.3%\u003c/p\u003e \u003cp\u003e3.3%\u003c/p\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e50.0%\u003c/p\u003e \u003cp\u003e3.3%\u003c/p\u003e \u003cp\u003e6.6%\u003c/p\u003e \u003cp\u003e30.0%\u003c/p\u003e \u003cp\u003e10.0%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSeasonal use\u003c/p\u003e \u003cp\u003eequally rain and dry\u003c/p\u003e \u003cp\u003emainly rain\u003c/p\u003e \u003cp\u003erain only\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e73.3%\u003c/p\u003e \u003cp\u003e23.3%\u003c/p\u003e \u003cp\u003e3.3%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e100.0%\u003c/p\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e86.6%\u003c/p\u003e \u003cp\u003e6.6%\u003c/p\u003e \u003cp\u003e6.6%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe variables related to the washing of the sampled nets were also assessed. The proportion of nets washed was high (\u0026ge;\u0026thinsp;70%) at both sites at 12, 24 and 36 months (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). The mean number of washes in the last six months (all/if washed) was approximately 3.0 at both sites at 12, 24 and 36 months. The main soap used was a local soap bar, detergent or bleach at both sites at 12, 24 and 36 months.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eVariables Related to the Washing of Bioassay Test Nets, Mali, 2018\u0026ndash;2020\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12 months\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e24 months\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e36 months*\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKenieba/Yorkool\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;29\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEver washed\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e70.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e93.3%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e79.3%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWashes last 6 months (all)\u003c/p\u003e \u003cp\u003eMean\u003c/p\u003e \u003cp\u003eMedian\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.2\u003c/p\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.8\u003c/p\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.0\u003c/p\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWashes last 6 months (if washed)\u003c/p\u003e \u003cp\u003eMean\u003c/p\u003e \u003cp\u003eMedian\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4.5\u003c/p\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3\u003c/p\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.6\u003c/p\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSoap used\u003c/p\u003e \u003cp\u003ecountry soap bar\u003c/p\u003e \u003cp\u003edetergent or bleach\u003c/p\u003e \u003cp\u003emix\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e38.1%\u003c/p\u003e \u003cp\u003e52.3%\u003c/p\u003e \u003cp\u003e9.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e32.1%\u003c/p\u003e \u003cp\u003e57.1%\u003c/p\u003e \u003cp\u003e10.7%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e21.7%\u003c/p\u003e \u003cp\u003e43.4%\u003c/p\u003e \u003cp\u003e26.0%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKita/PermaNet 2.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEver washed\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e83.3%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e96.6%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e93.3%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWashes last 6 months (all)\u003c/p\u003e \u003cp\u003eMean\u003c/p\u003e \u003cp\u003eMedian\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.4\u003c/p\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.1\u003c/p\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.0\u003c/p\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWashes last 6 months (if washed)\u003c/p\u003e \u003cp\u003eMean\u003c/p\u003e \u003cp\u003eMedian\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.9\u003c/p\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.2\u003c/p\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.2\u003c/p\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSoap used\u003c/p\u003e \u003cp\u003ecountry soap bar\u003c/p\u003e \u003cp\u003edetergent or bleach\u003c/p\u003e \u003cp\u003emix\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e36.0%\u003c/p\u003e \u003cp\u003e64.0%\u003c/p\u003e \u003cp\u003e0.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e37.9%\u003c/p\u003e \u003cp\u003e27.5%\u003c/p\u003e \u003cp\u003e34.4%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e25.0%\u003c/p\u003e \u003cp\u003e50.0%\u003c/p\u003e \u003cp\u003e3.5%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eInsecticidal activity\u003c/h2\u003e \u003cp\u003eThe results for the determination of insecticide bioefficacy for Yorkool nets collected in Kenieba nets and PermaNet 2.0 nets collected in Kita 6, 12, 24 and 36 months are shown in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. At each point in time, the proportion of nets with optimal effectiveness (at least 95% K.D. or 80% mortality) was \u0026lt;\u0026thinsp;80% with both types of nets and at both sites (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The proportion of nets reaching minimal effectiveness (75% K.D. or 50% 24-h mortality) was \u0026gt;\u0026thinsp;80% at 6, 12, and 24 months, but at 36 months, it decreased with both types of nets and at both sites (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The proportions of nets with optimal and minimal effectiveness were similar (\u003cem\u003ep\u0026thinsp;\u0026gt;\u0026thinsp;0.05\u003c/em\u003e) for both types of nets during the 36-month survey (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Minimal effectiveness was acceptable at both sites until the 24-month assessment but decreased dramatically at 36 months to 51.7% and 60%, respectively, with Yorkool nets in Kenieba and PermaNet 2.0 in Kita (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCone bioassay results using a susceptible colony of \u003cem\u003eAn. coluzzii\u003c/em\u003e on Yorkool and PermaNet 2.0 ITNs, Mali, 2018\u0026ndash;2020\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSite/Net\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6 months (Baseline)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12 months\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e24 months\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e36 months\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKenieba/Yorkool\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003eN\u0026thinsp;=\u0026thinsp;29\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKD60\u003c/p\u003e \u003cp\u003eMean (95% CI)\u003c/p\u003e \u003cp\u003eMedian (IQR)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e94.6% (90.5\u0026ndash;98.6)\u003c/p\u003e \u003cp\u003e98% (94.0-99.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e85.6% (78.2\u0026ndash;93.5)\u003c/p\u003e \u003cp\u003e94% (82-99.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e90.5% (83.5\u0026ndash;97.5)\u003c/p\u003e \u003cp\u003e96% (96.0-100.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e67.3% (55.2\u0026ndash;79.5)\u003c/p\u003e \u003cp\u003e78.0% (38.0\u0026ndash;96.0)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMortality 24 hours\u003c/p\u003e \u003cp\u003eMean (95% CI)\u003c/p\u003e \u003cp\u003eMedian (IQR)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e54.4% (47.8\u0026ndash;60.9)\u003c/p\u003e \u003cp\u003e54.0% (42.0\u0026ndash;66.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e74.1% (63.5\u0026ndash;84.7)\u003c/p\u003e \u003cp\u003e79% (72-89.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e54.2% (44.3\u0026ndash;64.2)\u003c/p\u003e \u003cp\u003e57.0% (44.2\u0026ndash;72.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e42.4% (29.7\u0026ndash;55.1)\u003c/p\u003e \u003cp\u003e36.0% (22.0\u0026ndash;60.0)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOptimal effectiveness\u003c/p\u003e \u003cp\u003eEstimate (95% CI)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e66.6% (45.8\u0026ndash;82.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e70.0% (47.9\u0026ndash;85.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e70.0% (47.9\u0026ndash;85.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e31.0% (15.1\u0026ndash;53.1)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMinimal effectiveness\u003c/p\u003e \u003cp\u003eEstimate (95% CI)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e96.6% (77.7\u0026ndash;99.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e100%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e93.3% (75.8\u0026ndash;98.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e51.7%(32.7\u0026ndash;70.1)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKita/PermaNet 2.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKD60\u003c/p\u003e \u003cp\u003eMean (95% CI)\u003c/p\u003e \u003cp\u003eMedian (IQR)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e94.9% (92.8\u0026ndash;96.9)\u003c/p\u003e \u003cp\u003e97.0% (94.0-100.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e93.7% (89.4\u0026ndash;98.1)\u003c/p\u003e \u003cp\u003e98% (94.2\u0026ndash;100)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e84.2% (76.5\u0026ndash;91.8)\u003c/p\u003e \u003cp\u003e95% (78.0-99.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e64.5% (53.7\u0026ndash;75.3)\u003c/p\u003e \u003cp\u003e66.0% (42.0\u0026ndash;94.0)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMortality 24 hours\u003c/p\u003e \u003cp\u003eMean (95% CI)\u003c/p\u003e \u003cp\u003eMedian (IQR)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e62.0% (53.6\u0026ndash;70.5)\u003c/p\u003e \u003cp\u003e59.0% (48.0\u0026ndash;72.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e71.2% (63.8\u0026ndash;78.6)\u003c/p\u003e \u003cp\u003e69% (64.2\u0026ndash;77.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e65.2% (57.2\u0026ndash;73.3)\u003c/p\u003e \u003cp\u003e62.0% (58.2\u0026ndash;74.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e39.8% (33.8\u0026ndash;45.8)\u003c/p\u003e \u003cp\u003e40.0% (28.0\u0026ndash;54.0)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOptimal effectiveness\u003c/p\u003e \u003cp\u003eEstimate (95% CI)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e66.6% (53.1\u0026ndash;77.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e76.6% (48.9\u0026ndash;91.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e56.6% (37.0-74.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e20.0% (8.0-41.5)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMinimal effectiveness\u003c/p\u003e \u003cp\u003eEstimate (95% CI)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e100.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e100%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e96.6% (77.7\u0026ndash;99.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e60.0% (38.9\u0026ndash;77.8)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eInsecticide surface level\u003c/h2\u003e \u003cp\u003eThe mean surface concentrations of insecticide residue on ITNs collected at 6 (baseline), 12, 24 and 36 months and measured by C-Vue are presented in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. The surface concentration of insecticide residue was greater in Yorkool nets (0.69 mg/m\u003csup\u003e2\u003c/sup\u003e) than in PermaNet 2.0 nets (0.46 mg/m\u003csup\u003e2\u003c/sup\u003e) (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.0211) at 6 months, but it was approximately the same in Yorkool nets (0.20 mg/m\u003csup\u003e2\u003c/sup\u003e) and in PermaNet 2.0 nets (0.24 mg/m\u003csup\u003e2\u003c/sup\u003e) (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.1907) at 12 months. The estimated contents remained similar for both types of nets across the survey: Yorkool nets (0.19 mg/m\u003csup\u003e2\u003c/sup\u003e) and PermaNet 2.0 nets (0.17 mg/m\u003csup\u003e2\u003c/sup\u003e) (\u003cem\u003ep\u0026thinsp;=\u0026thinsp;0.7901\u003c/em\u003e) at 24 months and at 36 months (0.08 and 0.06 mg/m\u003csup\u003e2\u003c/sup\u003e - Yorkool-PermaNet 2.0, \u003cem\u003erespectively\u0026mdash;p\u0026thinsp;=\u0026thinsp;0.1808\u003c/em\u003e) (Fig.\u0026nbsp;3).\u003c/p\u003e \u003cp\u003eBy converting surface levels to total levels of deltamethrin, the mean concentration decreased from 55 mg/m\u003csup\u003e2\u003c/sup\u003e (100.0%) to 29 mg/m\u003csup\u003e2\u003c/sup\u003e (71.0%), 28 mg/m\u003csup\u003e2\u003c/sup\u003e (72.5%) and 14 mg/m\u003csup\u003e2\u003c/sup\u003e (88.6%) at 6, 12, 24 and 36 months, respectively, for Yorkool nets. It decreased from 55 mg/m\u003csup\u003e2\u003c/sup\u003e (100.0%) to 29 mg/m\u003csup\u003e2\u003c/sup\u003e (47.8%), 28 mg/m\u003csup\u003e2\u003c/sup\u003e (63.0%), and 14 mg/m\u003csup\u003e2\u003c/sup\u003e (87.0%) at 6, 12, 24 and 36 months, respectively, for the PermaNet 2.0 nets (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eBy the end of the survey (36 months after distribution), the mean concentrations of available insecticide residue represented 11% (Yorkool nets) and 13% (PermaNet 2.0 nets) of the baseline insecticide concentration.\u003c/p\u003e \u003cp\u003e \u003cb\u003eFigure 3. Surface insecticide concentrations of the ITNs in Mali, 2018\u0026ndash;2020: (a) Kenieba/Yorkool and (b) Kita/PermaNet 2.0\u003c/b\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003e\u003cb\u003eChemical Content Results on Yorkool and PermaNet 2.0 ITNs, Mali, 2018\u0026ndash;2020\u003c/b\u003e\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6 months (Baseline)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12 months\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e24 months\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e36 months\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKenieba/Yorkool\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003eN\u0026thinsp;=\u0026thinsp;29\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eConverted total levels of insecticide (mg/m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e% Decrease compared to baseline\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e71.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e72.5%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e88.4%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKita/PermaNet 2.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003eN\u0026thinsp;=\u0026thinsp;30\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eConverted total levels of insecticide (mg/m\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e% Decrease compared to baseline\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e47.8%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e63.0%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e87.0%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis ITN durability study aimed to compare the use practices and insecticidal durability of two communities following their distribution through a mass campaign. The nets distributed were multifilament polyester-based ITNs treated with 75-denier deltamethrin (Yorkool) or 100-denier deltamethrin (PermaNet 2.0). To assess the influence of the net use environment and behavioral factors, this study was conducted in two health districts, Kenieba and Kita, located in the Kayes Region, which have similar malaria epidemiological, climatic, and socioecological profiles.\u003c/p\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003eNet use practices\u003c/h2\u003e \u003cp\u003eThe locations where nets were found (Hanging loose, hanging folded/tied, and not hanging) were similar at 12 and 36 months. However, the location of the net was different at 24 months, with a greater proportion of net hanging loose in Kita than in Kenieba. The risk of net physical damage increases when hanging loose or not hanging after use. This risk was high at each survey time at both sites. The main type of sleeping place was a bed frame (bamboo sticks) at both sites at the 12-, 24- and 36-month surveys. A similar result was found with the Magnet and PermaNet 2.0 study in Ethiopia [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] and in the Democratic Republic of Congo with DawaPlus 2.0 and DuraNet study [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. This type of sleeping place increases the risk of net physical damage because some holes that form in the ITN are mechanical (such as sharp materials and bed edges) [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. In most instances, the primary users of nets were older children (\u0026gt;\u0026thinsp;13 years old) and adults. This was unexpected because the primary users of nets are young children only and young children and adults. Similar results were observed in a study on Olyset and PermaNet 2.0 in Tanzania [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe proportion of nets used last night was lower in Kenieba (where the nets were Yoorkol) than in Kita (where the nets were PermaNet 2.0) at 12 and 24 months but similar at 36 months. However, the net use decreased between 12 and 36 months at both sites. The same results were observed for the proportion of nets used in the last week. There was no evidence of seasonal variation in net use, with nets used equally in both sites during the rainy and dry seasons.\u003c/p\u003e \u003cp\u003eThe proportion of nets washed was high (\u0026gt;\u0026thinsp;70%) at both sites at 12, 24 and 36 months. The mean number of washes in the last six months (all/if washed) was moderate, at approximately 3.0 at both sites at 12, 24, and 36 months. Similar results were observed in the Democratic Republic of the Congo with DawaPlus 2.0 in the DuraNet study [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. The main soap used was country soap bar, detergent, or bleach at both sites at 12, 24, and 36 months. One factor that could have contributed to the rapid decrease in insecticide use is the use of detergent or bleach [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003eInsecticidal effectiveness using the WHO Cone\u003c/h2\u003e \u003cp\u003eBased on the WHO [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] criteria at each survey, the proportion of Yorkool and PermaNet 2.0 nets with optimal effectiveness (at least 95% K.D. or 80% mortality) was \u0026lt;\u0026thinsp;80%. The proportion of both types of nets reaching minimal effectiveness (75% K.D. or 50% 24 h mortality) was \u0026gt;\u0026thinsp;80% at 6, 12, and 24 months but decreased radically at 36 months, decreasing to 52% with Yorkool and 60% with PermaNet 2.0. The proportions of nets with optimal and minimal effectiveness were similar for both types of nets during the entire study period, despite the differences in handling and use patterns observed in the sampled sites. These results contrast with those of studies conducted in Ethiopia, where MAGNET and PermaNet 2.0 retained their optimal effectiveness for up to 24 months [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Likewise, in Tanzania, the insecticidal durability of PermaNet 2.0 was excellent, with mean 60-min knockdown rates greater than 95% in WHO cone bioassay tests at all time points and a moderate decline in mean 24-h mortality rates from 93% at 12 months to 72% at 33 months (Haji et al., 2020). In the Democratic Republic of the Congo, the insecticidal effectiveness of DuraNet remained high throughout the follow-up and exceeded 80% of the optimal effectiveness at the 31-month assessment [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Similar results have also been reported for DuraNet from northern Tanzania, where these nets still had 94% mortality in bioassays after 20 washes [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], and at two sites in Nigeria where there was 97% optimal effectiveness after 36 months [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. The insecticidal performance of Royal Sentry and MAGNet in Mozambique was also good up to the 24-month follow-up but declined at 36 months when only 3% of the samples showed optimal effectiveness in Inhambane, 11% in Tete, and 29% in Nampula. However, 96% of ITNs still had minimal effectiveness at 36 months [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eBased on the PMI [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] guidelines, if less than 80% of the nets meet the optimal effectiveness criteria, the PMI recommends checking whether at least 80% of the nets meet the minimal effectiveness criteria. This is not an official WHO-established threshold, but it can provide a good assessment of how badly the efficiency of the nets is failing. If more than 80% of ITNs meet the minimal effectiveness evaluation criteria (75% K.D. or 50% 24-hour mortality), then there is a potential problem with the bioefficacy of ITNs, and further investigation of likely causes should be performed. If less than 80% of nets meet minimal effectiveness evaluation criteria, then a significant problem with the bioefficacy of the nets is very likely, and urgent investigation related to the possible causes should be performed. This study revealed that potential causes could include the use of country soap, a detergent, or bleach.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003eInsecticidal effectiveness using HPLC\u003c/h2\u003e \u003cp\u003eThe HPLC C-VUE method [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] showed that the mean deltamethrin concentration in Yorkool and PermaNet 2.0 nets decreased significantly over the study period. This value was below the WHO specification (WHO, 2021). At the end of the survey (36 months after distribution), the mean concentrations of available insecticide residue represented 11% (Yorkool nets) and 13% (PermaNet 2.0 nets) of the baseline insecticide concentration. Similar results were found in Ethiopia with MAGNet and PermaNet 2.0 using the Collaborative International Pesticide Analytical Council (CIPAC) method 454/LN/M/3.2 [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. After 24 and 36 months, the mean chemical concentrations of alphacypermethrin and deltamethrin were 23.86% and 24.64% of the baseline concentration, respectively [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. In Mozambique, with MAGNet and Royal Sentry nets, chemical testing of 36-month samples following the CIPAC method 454/LN/M/3.2 (WHO, 2021) revealed that the alphacypermethrin concentrations were 81%, 42% and 32% of the target dose [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. In Nigeria, with DawaPlus net, following the CIPAC method 454/LN/M/3.2(WHO, 2021), the chemical residue of deltamethrin after 12 months was 55% and 46% of the initial loading dose [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. In Kenya, at the end of years 1, 2 and 3 of Olyset Plus net usage, the permethrin content decreased by 36%, 40% and 52%, respectively, and the PBO content markedly decreased by 66%, 81%, and 87%, respectively. The loss of permethrin in Olyset Net was 16% in year one and did not change much in years 2 and 3 (19% and 24%, respectively) [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eYorkool and Permanent 2.0 nets did not meet the WHO criteria of optimal effectiveness for the bioefficacy of ITNs in this 3-year survey, which could have resulted from the rapid loss of deltamethrin, as users did not follow the manufacturer's recommendations to not wash nets with local soap, detergent or bleach. Better community education is therefore essential to ensure the appropriate use and care of nets in areas with ITN-based interventions to maximize the operational impact on the prevention, control, and elimination of malaria. Failure to preserve the efficacy of nets would have operational implications, requiring early replenishment with new nets to ensure that such an ITN-based malaria intervention remains effective. The C-Vue portable chromatographic device was used successfully for the first time in Mali to measure the surface-level insecticide concentration of ITNs. These results were consistent with those of cone bioassays. This new technology allows for an affordable and locally available, nondestructive method to monitor the insecticide content of ITN in malaria-endemic countries.\u003c/p\u003e"},{"header":"List Of Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eITN\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eInsecticide Treated Net\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003ePMI\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003ePresident Malaria Initiative\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eWHO\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eWorld Health Organization\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eCIPAC\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eCollaborative International Pesticide Analytical Council\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eHPLC\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eHigh-Performance Liquid Chromatography\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eWHOPES\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eWorld Health Organization Pesticide Evaluation Scheme\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eKD\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eKnock Down\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eCE\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eComite Ethique\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eINRSP\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eInstitut National de Recherche en Sante Publique\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eSL\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eSurface Level\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eTL\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eTotal Level\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthical clearance\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study protocol was translated into French and presented to the Mali National Institute of Public Health Research ethical committee for review. The clearance data were obtained on January 22, 2018, under reference number 02/2018/CE-INRSP. The staff implementing this study complied with all the policies and procedures of both the PMI and the local ethics board. Informed oral consent was obtained from all participants in this study prior to conducting the interviews.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and analyzed during the current study are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was made possible by the support of the American people through the United States Agency for International Development (USAID) and the U.S. President's Malaria Initiative (PMI) under contract No: AID-OAA-I-17-00008. The contents do not necessarily reflect the views of USAID, PMI, or the United States Government.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors' contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDesign of the study and tools: MBMC; I.T.; PM implementation and supervision: MBMC; I.T., MS, Y.D., A.D., JMS, S.S., A.D. and OK; bioassay: MBMC, I.T., MS, Y.D., A.D., JMS; and L.K.; chemical testing: MBMC; IT and Y.D., L.K.; analysis and interpretation: MBM, TSA; I.T and L.S., manuscript: all.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe want to thank all the staff involved in this study and support it at the international, national, regional, and community levels. Special thanks go to the chief medical officer of the Kenieba and Kita health districts and VectorLink Mali staff.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eLengeler C (2000) Insecticide-treated bednets and curtains for preventing malaria. Cochrane Database Syst Rev. ;(2):CD000363\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRandriamaherijaona S, Bri\u0026euml;t OJT, Boyer S, Bouraima A, N\u0026rsquo;Guessan R, Rogier C et al (2015) Do holes in long-lasting insecticidal nets compromise their efficacy against pyrethroid resistant Anopheles gambiae and Culex quinquefasciatus? Results from a release-recapture study in experimental huts. Malar J. 28 ao\u0026ucirc;t. ;14:332\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWHO Guidelines for monitoring the durability of long-lasting insecticidal mosquito nets under operational conditions [Internet]. 2011 [cit\u0026eacute; 15 mars 2024]. Disponible sur: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.who.int/publications-detail-redirect/9789241501705\u003c/span\u003e\u003cspan address=\"https://www.who.int/publications-detail-redirect/9789241501705\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWHO (2015) Strat\u0026eacute;gie technique mondiale de lutte contre le paludisme 2016\u0026ndash;2030 [Internet]. Gen\u0026egrave;ve: Organisation mondiale de la Sant\u0026eacute;; [cit\u0026eacute; 15 mars 2024]. 33 p. Disponible sur: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://iris.who.int/handle/10665/176720\u003c/span\u003e\u003cspan address=\"https://iris.who.int/handle/10665/176720\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePMI (2023) U.S. President\u0026rsquo;s Malaria Initiative - Mali\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePMI (2013) President\u0026rsquo;s Malaria Initiative: Mali Malaria Operational Plan FY 2015\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eINSTAT (2018) Mali Demographic and Health Surveys. Bamako, Mali et Rockville Maryland, USA\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAfrican IRS, Project (2017) p Impact of New Combination LLIN Products on Entomological Measures of Malaria Transmission in Southern Mali. Bethesda, MD, USA; \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e\u003c/span\u003e\u003cspan address=\"http://www.abtassociates.com\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWHO (2013) WHO Guidance Note for Estimating the Longevity of Long-Lasting Insecticidal Nets in Malaria Control September 2013\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWHO (2013) Guidelines for laboratory and field-testing of long-lasting insecticidal nets [Internet]. [cit\u0026eacute; 15 mars 2024]. Disponible sur: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.who.int/publications-detail-redirect/WHO-HTM-NTD-WHOPES-2013.1\u003c/span\u003e\u003cspan address=\"https://www.who.int/publications-detail-redirect/WHO-HTM-NTD-WHOPES-2013.1\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWHO. WHO SPECIFICATIONS AND EVALUATIONS FOR PUBLIC HEALTH PESTICIDES, (2021) DELTAMETHRIN LONG-LASTING (INCORPORATED INTO FILAMENTS) INSECTICIDAL NET\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePMI (2017) LLIN Durability Monitoring | Toolkit and Data Repository for PMI-funded LLIN durability monitoring studies [Internet]. [cit\u0026eacute; 15 mars 2024]. Disponible sur: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.durabilitymonitoring.org/\u003c/span\u003e\u003cspan address=\"https://www.durabilitymonitoring.org/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTraore I, Cisse M, Sow M, Swamidoss I, Dansoko Y, Dembele A et al (2014) Evaluation of a Portable, Field-adapted, Spring-driven Chromatographic Device and Sampling Technique for Rapid Measurement of Deltamethrin Surface Levels on Insecticide-treated Nets\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHiruy HN, Irish SR, Abdelmenan S, Wuletaw Y, Zewde A, Woyessa A et al Durability of long-lasting insecticidal nets (LLINs) in Ethiopia. Malar J [Internet]. 26 mars 2023 [cit\u0026eacute; 18 oct 2023];22(1):109. Disponible sur: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1186/s12936-023-04540-3\u003c/span\u003e\u003cspan address=\"10.1186/s12936-023-04540-3\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMansiangi P, Umesumbu S, Etewa I, Zandibeni J, Bafwa N, Blaufuss S et al (2020) Comparing the durability of the long-lasting insecticidal nets DawaPlus\u0026reg; 2.0 and DuraNet\u0026copy; in northwest Democratic Republic of Congo. Malar J. 24 mai. ;19(1):189\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHaji KA, Khatib BO, Obi E, Dimoso K, Koenker H, Babalola S et al (2020) Monitoring the durability of the long-lasting insecticidal nets Olyset\u0026reg; and PermaNet\u0026reg; 2.0 in similar use environments in Zanzibar. Malar J. 24 mai. ;19(1):187\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAtieli FK, Munga SO, Ofulla AV, Vulule JM (2010) Wash durability and optimal drying regimen of four brands of long-lasting insecticide-treated nets after repeated washing under tropical conditions. Malar J 30 ao\u0026ucirc;t 9:248\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKayedi MH, Lines JD, Haghdoost AA, Vatandoost MH, Rassi Y, Khamisabady K (2008) Evaluation of the effects of repeated hand washing, sunlight, smoke and dirt on the persistence of deltamethrin on insecticide-treated nets. Trans R Soc Trop Med Hyg ao\u0026ucirc;t 102(8):811\u0026ndash;816\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSolomon T, Loha E, Deressa W, Balkew M, Gari T, Overgaard HJ et al (2018) Bed nets used to protect against malaria do not last long in a semi-arid area of Ethiopia: a cohort study. Malar J. 20 juin. ;17(1):239\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMahande AM, Msangi S, Lyaruu LJ, Kweka EJ (2018) Bio-efficacy of DuraNet\u0026reg; long-lasting insecticidal nets against wild populations of Anopheles arabiensis in experimental huts. Trop Med Health 46:36\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eE O FO, Oo SBBOJA O, Monitoring the physical and insecticidal durability of the long-lasting insecticidal net DawaPlus\u0026reg; 2.0 in three States in Nigeria. Malar J [Internet]. 30 mars 2020 [cit\u0026eacute; 15 mars 2024];19(1). Disponible sur: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://pubmed.ncbi.nlm.nih.gov/32228592/\u003c/span\u003e\u003cspan address=\"https://pubmed.ncbi.nlm.nih.gov/32228592/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAb\u0026iacute;lio AP, Obi E, Koenker H, Babalola S, Saifodine A, Zulliger R et al (2020) Monitoring the durability of the long-lasting insecticidal nets MAGNet and Royal Sentry in three ecological zones of Mozambique. Malar J. 17 juin. ;19(1):209\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGichuki PM, Kamau L, Njagi K, Karoki S, Muigai N, Matoke-Muhia D et al (2021) Bioefficacy and durability of Olyset\u0026reg; Plus, a permethrin and piperonyl butoxide-treated insecticidal net in a 3-year long trial in Kenya. Infect Dis Poverty. 20 d\u0026eacute;c. ;10(1):135\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[{"identity":"12d73baa-f23b-4432-b4fa-4677016e73a9","identifier":"10.13039/100000200","name":"United States Agency for International Development","awardNumber":"under contract No: AID-OAA-I-17-00008","order_by":0}],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"Laboratoire de Biologie Moléculaire Appliquée, Université des Sciences, Techniques et Technologies de Bamako, Bamako-Mali","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Insecticide-treated nets, minimal effectiveness, optimal effectiveness, insecticide content, field-adapted liquid chromatographic system C-Vue®","lastPublishedDoi":"10.21203/rs.3.rs-4749503/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4749503/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eMonitoring insecticide levels and physical integrity over time is essential for assessing the durability of insecticide-treated nets (ITNs), which largely depends on the net handling habits of users. This study aimed to determine the insecticide content and effectiveness of ITNs (Yorkool and PermaNet 2.0) at 6, 12, 24 and 36 months after mass distribution in Mali.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eAt 12, 24 and 36 months postdistribution from 2018 to 2020, 30 nets were randomly collected from households in the districts of Kenieba and Kita in the southern part of Mali, together with information about ITN use and washing practices. The insecticidal effectiveness of the ITNs was assessed with the World Health Organization (WHO) cone test using a laboratory-reared susceptible colony of \u003cem\u003eAnopheles coluzzii\u003c/em\u003e. The residual insecticide content was measured by a nondestructive sampling technique with a portable field-adapted liquid chromatographic system (C-Vue\u0026reg;) validated by running samples in parallel with standardized WHO HPLC methods.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eAt each time point, nets were washed an average of three times over the previous 6 months, most commonly using detergent or bleach. For Yorkool nets, the average deltamethrin concentration was 55 mg/m\u003csup\u003e2\u003c/sup\u003e at 6 months and gradually decreased to 14 mg/m\u003csup\u003e2\u003c/sup\u003e at 36 months. The values for the PermaNet 2.0 nets were 45 mg/m\u003csup\u003e2\u003c/sup\u003e at 6 months and 6 mg/m\u003csup\u003e2\u003c/sup\u003e at 36 months. Until the 24-month evaluation, the proportion of nets with minimal effectiveness (at least 75% Knock Down \"K.D.\" or 50% 24 h mortality) was greater than 80% for both net types and sites. According to the WHO criteria, the proportion of net who met the WHO optimal effectiveness criteria (at least 95% K.D. or 80% mortality) was less than 80%. The WHO standardized cone test and C-Vue evaluation demonstrated that net type effectiveness and insecticide content were consistently lower than expected at 3 years.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eThe nets did not meet the WHO criteria of optimal effectiveness for the efficacy of ITNs in this 3-year survey, and users washed nets with local soap containing detergent or bleach. The C-Vue portable chromatographic device was used successfully for the first time in Mali to measure the insecticide concentration of ITNs. These results were consistent with those of cone bioassays.\u003c/p\u003e","manuscriptTitle":"Use of a portable field-adapted liquid chromatographic system (C-Vue machine) to estimate the quantity of deltamethrin on insecticide-treated nets paired with WHO cone bioassays to determine ITN bioefficacy as part of three-year durability monitoring in Mali","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-07-18 08:10:19","doi":"10.21203/rs.3.rs-4749503/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"f35cce20-d386-498d-bbca-cde3cfe68f8d","owner":[],"postedDate":"July 18th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":34682954,"name":"Entomology"}],"tags":[],"updatedAt":"2024-07-18T08:10:20+00:00","versionOfRecord":[],"versionCreatedAt":"2024-07-18 08:10:19","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4749503","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4749503","identity":"rs-4749503","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}