Burden and determinants of asymptomatic malaria among adults living in urban and rural areas in Gabon in 2023: a community-based cross-sectional study

Burden and determinants of asymptomatic malaria among adults living in urban and rural areas in Gabon in 2023: a community-based cross-sectional study | 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 Burden and determinants of asymptomatic malaria among adults living in urban and rural areas in Gabon in 2023: a community-based cross-sectional study Bridy Chesly Moutombi Ditombi, Noé Patrick M’Bondoukwe, Jacques Mari Ndong Ngomo, and 9 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7052550/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 24 Dec, 2025 Read the published version in Malaria Journal → Version 1 posted 9 You are reading this latest preprint version Abstract Background: Asymptomatic malaria represents a major challenge for malaria control and elimination efforts, particularly in endemic regions such as Gabon, where adult reservoirs are under-investigated. This study aimed to assess the burden and determinants of asymptomatic Plasmodium falciparum infection among adults in urban and rural communities in Gabon. Methods: A community-based cross-sectional survey was conducted between January and December 2023 in Bitam (rural), Libreville, and Owendo (urban). Adults aged ≥18 years with no malaria symptoms or recent antimalarial treatment were included. Demographic, socio-economic, and ITN-use data were collected via structured questionnaire. Malaria was diagnosed by microscopy. Logistic regression models were used to identify factors associated with asymptomatic infection. Results: Among 1,496 participants, the overall prevalence of asymptomatic P. falciparum infection was 15.3%, significantly higher in rural areas (22.4%) than in urban settings (4.1%; p<0.01). Parasite densities were also higher in rural participants. Independent risk factors included rural residence (aOR: 7.1; 95% CI: [4.4–9.8]), being a worker (aOR: 5.2; 95% CI: [3.4–7.8]), and having primary or secondary education (aOR: 2.6; 95% CI: [1.6–4.0]). ITN use was low (32.7%) and not significantly protective in multivariate analysis. Conclusion: The substantial burden of asymptomatic malaria in adults, particularly in rural Gabon, underscores the need to broaden malaria control strategies. These interventions must be tailored to adult populations, considering occupational exposure and local transmission dynamics. Expanding screening and improving ITN access and use are critical to reduce the hidden reservoir and achieve malaria elimination. Asymptomatic malaria Plasmodium falciparum adults rural–urban disparity Gabon CONTEXT Malaria remains a major public health problem in Sub-Saharan Africa (SSA), the WHO African region an estimated 246 million malaria cases in 2023, accounted for about 95% of global cases [1]. In Gabon, a malaria endemic country, malaria is the cause of one third or half of fever case in outpatients or inpatients, P.falciprum is the predominant species. Since the adoption and implementation of artemisinin-based combination therapies (ACT) for the treatment in 2005, along with insecticide-treated nets (ITNs) and sulfadoxine-pyrimethamine for intermittent preventive treatment (IPTp-SP) changes in malaria have been observed. Furthermore, heterogenicity of malaria exist in the country as revealed by data from the different sites notably in: Oyem, Libreville, Lambaréné, Makokou and Franceville [2,3]. A decrease of malaria prevalence as well as a change in the average age of infected patients was observed in Libreville as early as 2005 [2;4]. In 2011, a rebound in malaria prevalence was observed among patients under 10 years of age in rural area (44%), urban sentinel sites (25%) [2]. Then, this prevalence remained unchanged in Libreville as well as in the other cities of the country. However, there is a significant morbidity among older children and adults. Since almost 5 years in Gabon, a increasing malaria burden is reported in urban and rural settings [5,6]. The epidemiology of malaria is characterised by significant variability between urban and rural areas. Urbanisation, socio-economic conditions, and environmental factors contribute to differing transmission dynamics. For instance, while urban areas may benefit from better access to healthcare and preventive measures, they also face challenges such as increased population density and mobility, which can enhance transmission. Conversely, rural areas often experience higher transmission rates due to limited access to healthcare and preventive resources, and a greater reliance on traditional practices. Asymptomatic malaria poses a challenge for malaria control and elimination, as Plasmodium ( P . ) asymptomatic carriers represent a non negligeable parasite reservoir [7]. It is estimated that overall prevalence of asymptomatic malaria in children is 25% in Sub-Saharan Africa [8]. Such individuals become a reservoir for parasite transmission and may act as a precursor of symptomatic malaria. The potential of asymptomatic infections to sustain transmission have an impact on malaria efforts [9]. Factors such as the use of insecticide-treated nets (ITNs), educational attainment, and occupational status play crucial role in influencing the prevalence of asymptomatic malaria. Studies have shown that the use of ITNs can significantly reduce malaria transmission, yet their effectiveness is often inconsistent in urban settings where uptake may be lower [10,11]. Despite extensive data from East and West Africa, the epidemiology of asymptomatic malaria in Central Africa, including Gabon, remains poorly documented. Moreover, data from adult population are critically lacken. Such elucidating information’s will help for a better design efficient strategic target intervention to reduce the burden of the disease in Gabon. This study aims to determine the frequency of microscopic asymptomatic malaria infection and associated factors in urban compared to rural population. PATIENTS AND METHODS Study areas and study period A community based cross-sectional study was conducted in rural and urban areas in Gabon between January and December 2023. The rural site was Bitam, province is a city in the north of Gabon in the Woleu-Ntem province about 30 km from the Cameroonian border and not far from Equatorial Guinea, is located 146 km from Libreville. Two urban sites were selected, Libreville, the capital city of Gabon which, is situated on the borders of the Guinea gulf in West Central Africa and of Komo River. Secondly, Owendo city which is located 20 km from Libreville was also selected. Gabon as an equatorial climate, average temperatures remain relatively constant throughout the course of the year, with an average of 30°C. Malaria transmission is stable and perennial, with small fluctuations. Study population In rural area, a household community survey was performed in seventeen villages of Bitam by the team of Department of Parasitology – Mycology and Tropical Medicine of Université des Sciences de la Santé du Gabon. In urban areas, enrolled participants were volunteer participants to a STEP wise survey conducted at the Operational Research and Clinical Unit (ORCU) at the Regional Hospital Melen in Libreville and in a community health center in Owendo. Sample size calculation A convenience sampling approach was performed to recruit participants from both urban and rural settings. To ensure a sufficient sample size for detecting the expected prevalence of asymptomatic malaria infection, a minimum required sample size was estimated using the single population proportion formula: n = (Z² × p × (1 – p)) / d² Where: n is the estimated sample size, Z is the Z-score for the desired confidence level (1.96 for 95%), p is the estimated prevalence of asymptomatic malaria, d is the acceptable margin of error (5%). In the urban sites (Libreville and Owendo), a prevalence of 15% was assumed based on previously reported data [12]. With a 5% margin of error and 95% confidence level, the estimated minimum sample size was 196 participants. In rural communities (Bitam), a higher prevalence of 30% according to Biteghe et al, in 2024 was assumed [5]. Therefore, the study aimed to recruit at least: 200 participants in the urban sites (Libreville plus Owendo), 320 participants in rural site (Bitam). These thresholds were considered sufficient to explore the prevalence and potential risk factors of asymptomatic malaria, despite the non-random nature of participant selection. Inclusion criteria Apparently healthy, individuals who were permanent resident for at least two years in the study area, aged over 18 years, with no history of antimalarial treatment in the four weeks prior to the surveys were included. Based on the data of the sentinel site that report a history of fever of even 14 days prior to the diagnosis of clinical malaria, those participants with a history of fever during the 15 days prior to the study were not included [6]. Data collection A short, structured questionnaire was administered to collect demographic and socio-economic data including age, sex, residential area (rural, urban), occupation and educational level. Participants were also asked about their use of ITNs. Peripheral blood samples were collected for malaria detection and haemoglobin measurement. Biological Procedures Malaria diagnosis Thick and thin-blood smears were prepared and stained with 10% Giemsa for 15 minutes. Thick smears were screened for the presence of Plasmodium parasites following to the Lambarene’s method as previously described [6]. After air-drying, the stained slides were examined under oil-immersion, to detect and identify Plasmodium parasites. Parasitaemia was expressed as the number of parasites per microliter of blood (p/µL). A slide was considered negative if no parasite was seen in 100 oil-immersion fields. Quality control was performed by the slide reading by two independents well trained microscopists; the second reader was blinded to the initials results. In case of discrepancies, slides were re-examined by a third reader, and the parasitaemia of the two closest parasitemia was taken. The case definition of Plasmodium infection was a slide with the confirmed presence of Plasmodium sp . Hematological parameters measurement Haemoglobin (Hb) level was measured using a portable analyser ABX HORIBA Micros 60 in rural areas, and in urban areas, by using a Sysmex XN 350 automate analyser. Definitions Asymptomatic malaria was defined for a person with no recent history of symptoms and/or signs of malaria, with laboratory confirmation of parasitaemia. Infection was considered asymptomatic when the individuals body temperature was under 37.5°C at presentation and there was no history of fever within the last 14 days. The WHO criteria used to defined anaemia: haemoglobin (Hb) ≤11g/dL, 10.1-9 g/dL as mild, 8.0-5.0g/dL as moderate, and <5.0g/dL is regarded as severe malaria. Ethical considerations This study was part of the CANTAM 3 EPI project which was reviewed and approved by National Ethic Committee for research ( PROT N027/2022/CNE/SG-P ). Written informed consent was obtained from all participants before their inclusion in the study. Parents or legal guardians signed on behalf of adolescents their gave their assent. All procedures were conducted in accordance with the ethical guidelines of Helsinki declaration. Malaria diagnosis was free, and infected patients were treated with artemisinin-based combination therapies (ACT). Data analysis Data were double entered into Excel Microsoft sheet and analysed using R software. Descriptive analysis were conducted to summarise the characteristics of the study population. The prevalence of asymptomatic malaria was determined. Differences in prevalence and parasitaemia levels between urban and rural areas were assessed using Chi-Square Test for categorical variables and Kruskal-Wallis Test or ManWithney Test for continuous variables. Bivariate and multivariate logistic regression analyses were performed to investigate the association with sociodemographic factors and ITN use (independent variables) and asymptomatic microscopic Plasmodium infection (dependant variable). In order to control for confounders, the independent variables found associated with the dependant variable in the bivariate analysis with a p -value below 0.20 were used for the multivariate logistic regression analysis. Crude (cOR) or adjusted (aOR) odds ratio were presented together with their 95% confidence intervals (95% CI). A significance level of p<0.05 was considered statistically significant. RESULTS Characteristics of study participants A total of 1496 participants were enrolled in this study, 965 (64.5%) in rural and 531 (35.5%) in urban sites. Women predominated; the sex ratio was 0.6. The participant median age was 44 [32-56] years, 42.6% (n= 638/1496) were aged under 55 years. ITNs use was mostly infrequent (Tableau I). Hb levels could be measured in 824 participants, the frequency of anaemia was 22.7% (n=187/824). The median Hb level was 12.3[11.0-13.3] g/dL without difference between rural (12.0[10.6-14.0] g/dL and urban (12.4[11.3-13.4] g/dL) communities (p=0.24). Among the 187 anaemic individuals 55.1% (n=103) had moderate anaemia. Prevalence of asymptomatic malaria Overall, 238 (15.3%) participants had microscopically confirmed Plasmodium asymptomatic infection. P. falciparum was the only species identified. Malaria prevalence was significantly higher in rural compared to urban sites ( p<0.01 ) (Table 2). Regarding parasite density, it was 20[14-30] p/µL in participants with a positive blood smear. The majority (95.4%; n=206/216) of those living in Bitam had parasitaemia above 100/µL, whereas for those from Libreville and Owendo (68.2%; n=15/22) it was more often below 100p/µL ( p<0.01 ). Asymptomatic malaria and sociodemographic factors Last level of school attended was significantly associated with P. falciparum infection, individuals with primary or secondary school level having the highest prevalences and median parasite densities (p<0.01) (Table II). A trend towards higher prevalence and parasitaemia wad also observed in men and individuals over 55 years of age (Table II). Bivariate analysis showed that none, primary or secondary school level, being worker or unemployed, residing in rural area were significantly associated with higher odds of asymptomatic malaria (Table II). The multivariate logistic regression analysis confirmed that education, residing area, professional status were risks factors for P. falciparum asymptomatic infection in the study population. Compared to urban community, rural inhabitants had seven times (aOR:7.1[4.4-9.8]; p<0.01) higher risk of asymptomatic malaria. The risk of malaria was 5 times higher in workers compared to unemployed participants (aOR: 5.2[3.4-7.8]; p<0.01). It was more than 2 times higher in people with primary school or secondary school (aOR: 2.6[1.6-4.0]; p<0.01). Asymptomatic malaria prevalence according to ITNs use and Hb level No significant difference was observed between ITN users and non-users (Table II). The median Hb level was 12.3[11.0-14.0] g/dL in participants with a positive blood smear and 12.3 [11.0-13.6] g/dL in the uninfected ones (p=0.69). Similarly, the rate of anaemic participants was comparable in the presence (21.8%; n=24/110) or in the absence (22.8%; n=163/715) of Plasmodium parasitaemia (p=0.92). There was no difference in parasite density between anaemic and non-anaemic participants (p=0.78). Comparison between rural and urban communities The association between the socio-demographics factors, ITN use, and the rate of positive blood smear was assessed according to the residence area, revealing different risk factors. In urban community, only being unemployed was identified as a significant risk factor for asymptomatic malaria (Table III). This association remained significant after the multivariate logistic regression (aOR:3.4 IC95%: [1.1-7.1]; p=0.03 ) Among inhabitants from Bitam, the rural city, the unemployed ones had the lowest rate of P. falciparum infection. Whereas having attended any school level was predictor of the disease, in bivariate and in multivariate analysis (primary school: aOR:5.0 IC95% [2.0-8.3]; secondary school: aOR: 5.0 IC95% [2.4-9.0]; university: aOR:5.0 IC95% [1.3-11.2]) compared to those who had never attended school ( p<0.01 ). (Table III) Regarding the professional status, managers were at lower risk of contracting asymptomatic malaria, with being worker at 1.8 times (aOR:1.8 IC95% [0.96-4.2]; p=0.05 ) at higher risk of presenting with asymptomatic malaria during the study period (Table III). ITN use and age were no longer found significantly associated with malaria when taking account the confounders, in the multivariate analysis either in urban or in rural settings. DISCUSSION Almost 20 years after implementation of ITN, IPTp-SP and ACT in Gabon, malaria transmission remains high across the country. Data from rural and semi-urban areas report a resurgence of symptomatic malaria cases, which started prior to the COVID-19 pandemic [ 5 , 6 ] and increase thereafter. There are several challenges towards elimination of malaria, including low coverage of preventive measures, poor access to healthcare, drug and insecticide resistance, population and vector behaviors, the maintenance of parasite reservoir [ 13 – 15 ]. This study highlighted a substantial burden of asymptomatic malaria (15.9%) in adults from three communities in Gabon. This prevalence is similar to that reported in a study performed in 2013 in different settlements in Gabon (18.8%) as well as in Uganda (15.4%) in 2020 [ 16 , 17 ]. Other authors report higher prevalences in Cameroon (38.4%) and Kenya (42%) [ 18 , 19 ]. This difference could be attributed to the methodology used in the different studies, the study population, and the ecology of sites, as well as the level of malaria endemicity in the different study areas. The prevalence in the urban community was 4.1% slightly lower to that reported in 2019 at Owendo (5.9%) [ 12 ]. Urban environments after improved housing infrastructing such as sealed wells and screened windows. Urban dwellers have probably better knowledge of malaria risk and prevention. All these factors, including fewer suitable mosquitoes breeding sites, reduce exposure to the vectors. The higher prevalence of asymptomatic malaria observed in Libreville and Owendo, compared to the rural city of Bitam is consistent with findings across others sub-Saharan Africa. Rural residents were thus more than six times more likely to harbor asymptomatic infection, underscoring a persistent local transmission intensity. Indeed, urban environments are less favorable to vector species, particularly An. gambiae , which has a strong preference for clean water. Actually, the increasing insalubrity and polluted water in the greater Libreville area are leading cause of reduction in the Anopheles population. Considering that malaria diagnosis was performed using only microscopic techniques, the prevalence of asymptomatic carriage is very likely underestimated. A recent metanalysis reported that the prevalence of asymptomatic malaria among older children in Central Africa is approximately 30% [ 8 ]. Adults therefore represent a significant parasite reservoir in Libreville, most likely due to low ITN usage (19%) and more frequent exposure to mosquito bites compared to children. These findings highlight the need to raise awareness among this age group regarding malaria prevention, and to include them alongside young children and pregnant women in health education campaigns and mass ITN distribution programs. In rural areas, conditions are favorable to exposure to mosquito bites, so repeated exposure to the bites of infectious mosquitoes carrying malaria parasites makes the host's immune system better able to control parasite density, thus preventing the onset of clinical symptoms [ 20 ]. A study carried out in 2008 in several rural villages in Gabon reported an estimated overall prevalence of 6.2%, rising to 37.2% [ 21 ]. Although malaria transmission in Gabon, an heterogenicity of endemicity level is observed. Bitam is a hyperendemic zone, with much more vegetation, and the villages surveyed were close to forested areas, a propitious environment for vector multiplication. Indeed, environmental factors such as proximity to forest, household density and altitude tend to be significantly and positively correlated with malaria risk [ 22 ]. The high prevalence of asymptomatic malaria in rural areas could be due to exposure-related immunity, which occurs when people frequently exposed to parasites eventually develop premunition [ 23 ]. Sociodemographic factors were independently and differentially associated with asymptomatic malaria carriage in urban and rural communities. Men appeared more frequently infected than women, as previously reported by Kumari et al. in India [ 9 ]. This observation likely reflects gender-specific behavioural patterns. While women generally remain at home after work and during the night, men are more likely to engage in late-afternoon or overnight professional and social activities. In urban settings, they often stay outdoors beyond working hours, whereas in rural areas, they may spend the night in the forest for hunting or agricultural activities, or gather with other men in the “corps de garde” to socialise late into the night. These behaviours increase their exposure to mosquito bites. Occupational exposure appears to play a key role in the higher risk of asymptomatic malaria among rural male workers. Bitam, a forested area, is particularly prone to transmission, and overnight stays in the forest for hunting or farming, some well-established risk factors [24;18;8]. Additionally, specific occupations such as farming, hunting, guarding, housework, and studying were associated with increased asymptomatic carriage [25, 26. Interestingly, most unemployed individuals in urban settings were students, whereas in rural Bitam, the unemployed were mainly engaged in informal subsistence activities, including farming or hunting, often in the forested or in farm/bush around their house, thus, further increasing their exposure risk. Of particular note, individuals with secondary or university education, especially retirees who have returned to settle in villages, were frequently involved in managing their own plantations. These educated individuals often live off the proceeds of their agricultural production and spend long hours working outdoors. This could partly explain the unexpectedly higher prevalence of asymptomatic carriage among those with higher education levels compared to middle managers. These findings underline the importance of adapting malaria control strategies to behavioural and occupational contexts. Indeed, encouraging workplace intervention and the use of long-sleeved shirts and trousers during outdoor and forest-based activities, especially among men and farmers. Then, promoting ITN distribution and communication campaigns which specifically target adult men and older individuals, not just children and pregnant women. Moreover, tailoring health education to rural retirees and educated populations regarding the continued risk of malaria for retired individuals engaging in agricultural work, even if they consider themselves knowledgeable and community engagement in behavioural by Integrating malaria prevention into rural development schemes should be considered key interventions for malaria control in rural settings. [ 27 , 28 ]. Despite global efforts to promote the use of insecticide-treated nets (ITNs), the lack of protective effect against malaria may be attributable to suboptimal coverage (below 35%), improper usage, or the emergence of insecticide resistance, factors that warrant further investigation. A study conducted in Nigeria similarly found no significant association between ITN use and asymptomatic Plasmodium falciparum carriage [ 29 ]. In contrast, evidence from Cameroon and across sub-Saharan Africa suggests that not sleeping under an ITN or using it improperly is associated with at least a 3.5-fold increased risk of asymptomatic malaria [8; 30]. The interview did not investigate the condition of the net or the duration and frequency of use. Long-acting insecticide-impregnated nets (LLIN) provide both chemical and physical barriers against mosquitoes by reducing their contact with humans, however when damaged they become less effective against mosquito bites. Also, owning an LLIN is not always synonymous with good use, as the appropriate use of LLINs is one of the main cost-effective interventions for malaria prevention [ 31 ]. Although LLINs are considered an effective means of avoiding mosquito bites, their improper use and longevity could lead to the loss of their effectiveness and therefore LLINs no longer offer effective protection against malaria-vector mosquitoes [ 32 ]. In addition, the last net distribution campaigns in this region were more than three years ago, and with the occurrence of the COVID 19 pandemic, efforts were concentrated on the epidemic response. Despite some inconsistent findings, ITN use remains an effective strategy for preventing both asymptomatic and symptomatic malaria. Its promotion and the achievement of universal coverage should remain key local targets in efforts to move towards malaria elimination. Moreover, Strengthening community education on correct net use and exploring alternative vector control strategies are essential to enhance the overall effectiveness of malaria prevention interventions. Parasitemia levels were higher in rural areas than in urban areas, which may be explained by the fact that due to their greater exposure to infective mosquito bites than those living in urban areas and their acquired premunition, people living in rural areas are better able to withstand parasite densities. In addition, this anti-parasite immunity and premunition can help control parasite multiplication, thereby reducing parasite loads in adults. In a study conducted is Ashanti region of Ghana, participants living in urban areas had lower prevalence and parasite densities compared those residing in rural prevalence and peri urban settings [ 33 ]. In our local context, parasitemia were also lower than those typically reported among symptomatic patients in Gabon [ 5 ]. Chronic carriage with low or submicroscopic parasite densities contributes to the persistence of malaria transmission through these silent reservoirs. Moreover, a non-negligible proportion of these individuals may eventually develop symptomatic and life-threatening symptomatic diseases. This study has some limitations. The prevalence of asymptomatic plasmodial infection in this study may have been underestimated, as only microscopy was used for the diagnosis. Patients with submicroscopic infections may have been classified as negative, leading to an underestimation of the true prevalence of asymptomatic malaria. The convenience sampling may limit the generalizability and self-reporting of ITN use may introduce reporting bias. Nevertheless, this study is among the few to assess asymptomatic microscopic Plasmodium carriage in non-pregnant adults in endemic Central Africa. The large sample size and inclusion in both urban and rural settings strengthen the validity of our data that highlight important intervention gaps. Targeted strategies for adults’ populations including manual laborers and the unemployed as well as introduction of community-wide screening using ultra-sensitive RDT or molecular tools are importantly necessary. CONCLUSION A Gabon facies a resurgence in malaria incidence the present findings highlight the dual challenge of low adult targeted, ITN and other preventive measures coverage and rural, urban disparities in asymptomatic Plasmodium falciparum carriage. National control strategies must expand beyond clinical case management to include active surveillance and adult focused prevention to accelerate progress toward malaria control and elimination. Abbreviations P.falciparum Plasmodium falciparum ITN Insecticide-treated nets aOR adjusted odds ratio cOR crude odds ratio ACT Artemisinin-based combination therapies IPTp-SP Intermittent prevention treatment Sulfadoxine-Pyrimethamine Hb Haemoglobin RDT Rapid diagnostic test IC Intervale Confidence Declarations Acknowledgments We would like to thank the participants and all team from the Department of Parasitology-Mycology. Author contributions MBDC: conceptualized the study, conducted and acquisitions of data, interpreted analysis and wrote the first draft, edited the manuscript; NPM, JMNN, HNK, MAM, LNA and RM: data and sample collection, and performed microscopy; NPM and LNA: data analysis; DAMM and CJM: reported data on excel Microsoft sheet; BAMK: conceptualized and supervised the study, interpreted data and corrected the manuscript; DPMM: coordinated the microscopy analysis and revision the manuscript All authors reviewed and approved the final draft of the manuscript. Funding This study was a part of CANTAM-EPI 3 Availability of data and materials The datatests used and analysed in this study are available from the corresponding author. Consent for publication Not applicable Competing interests The authors declare no competing interests. References WHO. World Malaria Report 2024. Geneva: World Health Organization; 2024. Mawili-Mboumba DP, Bouyou Akotet MK, Kendjo E, Nzamba J, Medang MO, Mbina JR, et al . Increase in malaria prevalence and age of at risk population in different areas of Gabon. Malar J . 2013 Jan 2;12:3. doi: 10.1186/1475-2875-12-3. Assele V, Ndoh GE, Nkoghe D, Fandeur T. No evidence of decline in malaria burden from 2006 to 2013 in a rural Province of Gabon: implications for public health policy. BMC Public Health. 2015 Feb 4;15:81. doi: 10.1186/s12889-015-1456-4. Bouyou-Akotet MK, Mawili-Mboumba DP, Kendjo E, Mabika-Mamfoumbi M, Ngoungou EB, Dzeing-Ella A, et al. 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Transfusio n. 2020 May;60(5):955-964. doi: 10.1111/trf.15775. Djoufounna J, Mayi MPA, Bamou R, Foyet JV, Tabue R, Lontsi-Demano M, et al. High prevalence of asymptomatic Plasmodium falciparum malaria in Makenene, a locality in the forest-savannah transition zone, Centre Region of Cameroon. Curr Res Parasitol Vector Borne Dis . 2022 Nov 28;2:100104. doi: 10.1016/j.crpvbd.2022.100104. Salgado C, Ayodo G, Macklin MD, Gould MP, Nallandhighal S, Odhiambo EO, et al . The prevalence and density of asymptomatic Plasmodium falciparum infections among children and adults in three communities of western Kenya. Malar J. 2021 Sep 17;20(1):371. doi: 10.1186/s12936-021-03905-w. Carrasco-Escobar G, Qquellon J, Villa D, Cava R, Llanos-Cuentas A, Benmarhnia T. Time-Varying Effects of Meteorological Variables on Malaria Epidemiology in the Context of Interrupted Control Efforts in the Amazon Rainforest, 2000-2017. Front Med (Lausanne). 2021 Sep 29;8:721515. doi: 10.3389/fmed.2021.721515. Nkoghe D, Akue JP, Gonzalez JP, Leroy EM. Prevalence of Plasmodium falciparum infection in asymptomatic rural Gabonese populations. Malar J . 2011 Feb 9;10:33. doi: 10.1186/1475-2875-10-33. Haque U, Sunahara T, Hashizume M, Shields T, Yamamoto T, Haque R, et al . Malaria prevalence, risk factors and spatial distribution in a hilly forest area of Bangladesh. PLoS One. 2011 Apr 21;6(4):e18908. doi: 10.1371/journal.pone.0018908. Laishram DD, Sutton PL, Nanda N, Sharma VL, Sobti RC, Carlton JM, et al . The complexities of malaria disease manifestations with a focus on asymptomatic malaria. Malar J . 2012 Jan 31;11:29. doi: 10.1186/1475-2875-11-29. Kar NP, Kumar A, Singh OP, Carlton JM, Nanda N. A review of malaria transmission dynamics in forest ecosystems. Parasites Vectors. 20147 ; 265. https://doi.org/10.1186/1756-3305-7-265 Mbah CE, Ambe LA, Ngwewondo A, Kidzeru EB, Akwah L, Mountchissi C, et al. A Comparative Study of Asymptomatic Malaria in a Forest Rural and Depleted Forest Urban Setting during a Low Malaria Transmission and COVID-19 Pandemic Period. Biomed Res Int . 2022 Oct 15;2022:2545830. doi: 10.1155/2022/2545830. Egbewale BE, Akindele AA, Adedokun SA, Oyekale OA. Prevalence of asymptomatic malaria and anaemia among elderly population in Osun state Southwestern, Nigeria. International Journal Of Community Medicine And Public Health . 2018,5(7),2650–2656. https://doi.org/10.18203/2394-6040.ijcmph20182449 Seyoum TF, Andualem Z, Yalew HF. Insecticide-treated bed net use and associated factors among households having under-five children in East Africa: a multilevel binary logistic regression analysis. Malar J . 2023 Jan 7;22(1); Fambirai T, Chimbari M, Mhindu T. Factors associated with contracting border malaria: A systematic and meta-analysis. PloS One . 2025 Jan 3;20(1):e0310063 Onyiah AP, Ajayi IO, Dada-Adegbola HO, Adedokun BO, Balogun MS, Nguku PM, et al. (2018) Long-lasting insecticidal net use and asymptomatic malaria parasitaemia among household members of laboratory-confirmed malaria patients attending selected health facilities in Abuja, Nigeria, 2016: A cross-sectional survey. PLoS ONE 13(9): e0203686. https://doi.org/10.1371/journal.pone.0203686 Ibrahim AO, Agbesanwa TA, Aremu SK, Bello IS, Elegbede OT, Gabriel-Alayode OE, et al. Malaria infection and its association with socio-demographics, long lasting insecticide nets usage and hematological parameters among adolescent patients in rural Southwestern Nigeria. PLoS ONE. 2023 ;18(7): e0287723. https://doi.org/10.1371/journal.pone.0287723 Ngongang-Yipmo ES, Tchouakui M, Menze BD, Mugenzi LMJ, Njiokou F, Wondji CS. Reduced performance of community bednets against pyrethroid-resistant Anopheles funestus and Anopheles gambiae, major malaria vectors in Cameroon. Parasit Vectors. 2022 Jun 26;15(1):230. doi: 10.1186/s13071-022-05335-2. Hayuma PM, Wang CW, Liheluka E, Baraka V, Madebe RA, Minja DTR, et al . Prevalence of asymptomatic malaria, submicroscopic parasitaemia and anaemia in Korogwe District, north-eastern Tanzania. Malar J . 2021 Oct 29;20(1):424. doi: 10.1186/s12936-021-03952-3 Mutala AH, Badu K, Owusu C, Agordzo SK, Tweneboah A, Abbas DA, et al . Impact of malaria on haematological parameters of urban, peri-urban and rural residents in the Ashanti region of Ghana: a cross-sectional study. AAS Open Res . 2020 Jul 9;2:27. doi: 10.12688/aasopenres.12979.3. Tables Tables 1 to 3 are available in the Supplementary Files section. Additional Declarations No competing interests reported. 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Santé","correspondingAuthor":false,"prefix":"","firstName":"Denise","middleName":"Patricia","lastName":"Mawili-Mboumba","suffix":""},{"id":485261554,"identity":"919d433d-f4bb-4179-b785-bb69a8698aee","order_by":11,"name":"Marielle Karine Bouyou Akotet","email":"","orcid":"","institution":"Université des Sciences de la Santé","correspondingAuthor":false,"prefix":"","firstName":"Marielle","middleName":"Karine Bouyou","lastName":"Akotet","suffix":""}],"badges":[],"createdAt":"2025-07-05 10:53:05","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7052550/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7052550/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s12936-025-05672-4","type":"published","date":"2025-12-24T15:58:29+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":99172417,"identity":"2530ff78-8b23-49b2-a479-74d8411ee4e6","added_by":"auto","created_at":"2025-12-29 16:09:12","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":829404,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7052550/v1/df0d12cb-bcc9-4cb0-9b5a-ea87f76e8561.pdf"},{"id":86859990,"identity":"b80c7803-0099-4850-b23a-6fba12fa45ac","added_by":"auto","created_at":"2025-07-16 11:58:08","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":20772,"visible":true,"origin":"","legend":"","description":"","filename":"Tables.docx","url":"https://assets-eu.researchsquare.com/files/rs-7052550/v1/6cb24d849fb0c1cee2b45516.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Burden and determinants of asymptomatic malaria among adults living in urban and rural areas in Gabon in 2023: a community-based cross-sectional study","fulltext":[{"header":"CONTEXT","content":"\u003cp\u003eMalaria remains a major public health problem in Sub-Saharan Africa (SSA), the WHO African region an estimated 246 million malaria cases in 2023, accounted for about 95% of global cases [1]. \u0026nbsp;In Gabon, a malaria endemic country, malaria is the cause of one third or half of fever case in outpatients or inpatients, \u003cem\u003eP.falciprum\u0026nbsp;\u003c/em\u003eis the predominant species. Since the adoption and implementation of artemisinin-based combination therapies (ACT) for the treatment in 2005, along with insecticide-treated nets (ITNs) and sulfadoxine-pyrimethamine for intermittent preventive treatment (IPTp-SP) changes in malaria have been observed. Furthermore, heterogenicity of malaria exist in the country as revealed by data from the different sites notably in: Oyem, Libreville, Lambar\u0026eacute;n\u0026eacute;, Makokou and Franceville [2,3]. A decrease of malaria prevalence as well as a change in the average age of infected patients was observed in Libreville as early as 2005 [2;4]. In 2011, a rebound in malaria prevalence was observed among patients under 10 years of age in rural area (44%), urban sentinel sites (25%) [2]. Then, this prevalence remained unchanged in Libreville as well as in the other cities of the country. However, there is a significant morbidity among older children and adults.\u003c/p\u003e\n\u003cp\u003eSince almost 5 years in Gabon, a increasing malaria burden is reported in urban and rural settings [5,6]. The epidemiology of malaria is characterised by significant variability between urban and rural areas. Urbanisation, socio-economic conditions, and environmental factors contribute to differing transmission dynamics. For instance, while urban areas may benefit from better access to healthcare and preventive measures, they also face challenges such as increased population density and mobility, which can enhance transmission. Conversely, rural areas often experience higher transmission rates due to limited access to healthcare and preventive resources, and a greater reliance on traditional practices.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;Asymptomatic malaria poses a challenge for malaria control and elimination, as \u003cem\u003ePlasmodium\u003c/em\u003e (\u003cem\u003eP\u003c/em\u003e\u003cem\u003e.\u003c/em\u003e)\u0026nbsp;asymptomatic carriers represent a non negligeable parasite reservoir [7]. It is estimated that overall prevalence of asymptomatic malaria in children is 25% in Sub-Saharan Africa [8]. Such individuals become a reservoir for parasite transmission and may act as a precursor of symptomatic malaria. The potential of asymptomatic infections to sustain transmission have an impact on malaria efforts [9].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFactors such as the use of insecticide-treated nets (ITNs), educational attainment, and occupational status play crucial role in influencing the prevalence of asymptomatic malaria. Studies have shown that the use of ITNs can significantly reduce malaria transmission, yet their effectiveness is often inconsistent in urban settings where uptake may be lower [10,11].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eDespite extensive data from East and West Africa, the epidemiology of asymptomatic malaria in Central Africa, including Gabon, remains poorly documented. Moreover, data from adult population are critically lacken. Such elucidating information\u0026rsquo;s will help for a better design efficient strategic target intervention to reduce the burden of the disease in Gabon.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThis study aims to determine the frequency of microscopic asymptomatic malaria infection and associated factors in urban compared to rural population.\u003c/p\u003e"},{"header":"PATIENTS AND METHODS","content":"\u003cul\u003e\n \u003cli\u003e\u003cstrong\u003e\u003cem\u003eStudy areas and study period\u003c/em\u003e\u003c/strong\u003e\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eA community based cross-sectional study was conducted in rural and urban areas in Gabon between January and December 2023. The rural site was Bitam, province is a city in the north of Gabon in the Woleu-Ntem province about 30 km from the Cameroonian border and not far from Equatorial Guinea, is located 146 km from Libreville.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTwo urban sites were selected, Libreville, the capital city of Gabon which, is situated on the borders of the Guinea gulf in West Central Africa and of Komo River. Secondly, Owendo city which is located 20 km from Libreville was also selected.\u003c/p\u003e\n\u003cp\u003eGabon as an equatorial climate, average temperatures remain relatively constant throughout the course of the year, with an average of 30\u0026deg;C. Malaria transmission is stable and perennial, with small fluctuations.\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003e\u003cstrong\u003e\u003cem\u003eStudy population\u003c/em\u003e\u003c/strong\u003e\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eIn rural area, a household community survey was performed in seventeen villages of Bitam by the team of Department of Parasitology \u0026ndash; Mycology and Tropical Medicine of Universit\u0026eacute; des Sciences de la Sant\u0026eacute; du Gabon. In urban areas, enrolled participants were volunteer participants to a STEP wise survey conducted at the Operational Research and Clinical Unit (ORCU) at the Regional Hospital Melen in Libreville and in a community health center in Owendo.\u0026nbsp;\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003e\u003cstrong\u003e\u003cem\u003eSample size calculation\u003c/em\u003e\u003c/strong\u003e\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eA convenience sampling approach was performed to recruit participants from both urban and rural settings. To ensure a sufficient sample size for detecting the expected prevalence of asymptomatic malaria infection, a minimum required sample size was estimated using the single population proportion formula:\u003c/p\u003e\n\u003cp\u003e\u0026emsp;\u0026emsp;\u003cstrong\u003en = (Z\u0026sup2; \u0026times; p \u0026times; (1 \u0026ndash; p)) / d\u0026sup2;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWhere:\u003c/p\u003e\n\u003cul class=\"decimal_type\"\u003e\n \u003cli\u003en is the estimated sample size,\u003c/li\u003e\n \u003cli\u003eZ is the Z-score for the desired confidence level (1.96 for 95%),\u003c/li\u003e\n \u003cli\u003ep is the estimated prevalence of asymptomatic malaria,\u003c/li\u003e\n \u003cli\u003ed is the acceptable margin of error (5%).\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eIn the urban sites (Libreville and Owendo), a prevalence of 15% was assumed based on previously reported data [12]. With a 5% margin of error and 95% confidence level, the estimated minimum sample size was 196 participants. In rural communities (Bitam), a higher prevalence of 30% according to Biteghe et \u003cem\u003eal,\u003c/em\u003e in 2024 was assumed [5].\u003c/p\u003e\n\u003cp\u003eTherefore, the study aimed to recruit at least:\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003e200 participants in the urban sites (Libreville plus Owendo),\u003c/li\u003e\n \u003cli\u003e320 participants in rural site (Bitam).\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eThese thresholds were considered sufficient to explore the prevalence and potential risk factors of asymptomatic malaria, despite the non-random nature of participant selection.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cem\u003eInclusion criteria\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eApparently healthy, individuals who were permanent resident for at least two years in the study area, aged over 18 years, with no history of antimalarial treatment in the four weeks prior to the surveys were included. Based on the data of the sentinel site that report a history of fever of even 14 days prior to the diagnosis of clinical malaria, those participants with a history of fever during the 15 days prior to the study were not included [6].\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003e\u003cstrong\u003e\u003cem\u003eData collection\u003c/em\u003e\u003c/strong\u003e\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eA short, structured questionnaire was administered to collect demographic and socio-economic data including age, sex, residential area (rural, urban), occupation and educational level. Participants were also asked about their use of ITNs. Peripheral blood samples were collected for malaria detection and haemoglobin measurement. \u0026nbsp;\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003e\u003cstrong\u003e\u003cem\u003eBiological Procedures\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003e\u003cem\u003eMalaria diagnosis\u003c/em\u003e\u003c/strong\u003e\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eThick and thin-blood smears were prepared and stained with 10% Giemsa for 15 minutes. Thick smears were screened for the presence of \u003cem\u003ePlasmodium\u003c/em\u003e parasites following to the Lambarene\u0026rsquo;s method as previously described [6]. After air-drying, the stained slides were examined under oil-immersion, to detect and identify \u003cem\u003ePlasmodium\u003c/em\u003e parasites. Parasitaemia was expressed as the number of parasites per microliter of blood (p/\u0026micro;L). A slide was considered negative if no parasite was seen in 100 oil-immersion fields. Quality control was performed by the slide reading by two independents well trained microscopists; the second reader was blinded to the initials results. In case of discrepancies, slides were re-examined by a third reader, and the parasitaemia of the two closest parasitemia was taken. The case definition of \u003cem\u003ePlasmodium\u003c/em\u003e infection was a slide with the confirmed presence of \u003cem\u003ePlasmodium sp\u003c/em\u003e.\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003e\u003cstrong\u003e\u003cem\u003eHematological parameters measurement\u003c/em\u003e\u003c/strong\u003e\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eHaemoglobin (Hb) level was measured using a portable analyser ABX HORIBA Micros 60 in rural areas, and in urban areas, by using a Sysmex XN 350 automate analyser.\u0026nbsp;\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003e\u003cstrong\u003e\u003cem\u003eDefinitions\u003c/em\u003e\u003c/strong\u003e\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eAsymptomatic malaria was defined for a person with no recent history of symptoms and/or signs of malaria, with laboratory confirmation of parasitaemia. Infection was considered asymptomatic when the individuals body temperature was under 37.5\u0026deg;C at presentation and there was no history of fever within the last 14 days. \u0026nbsp;The WHO criteria used to defined anaemia: haemoglobin (Hb) \u0026le;11g/dL, 10.1-9 g/dL as mild, 8.0-5.0g/dL as moderate, and \u0026lt;5.0g/dL is regarded as severe malaria.\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003e\u003cstrong\u003e\u003cem\u003eEthical considerations\u003c/em\u003e\u003c/strong\u003e\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eThis study was part of the \u003cstrong\u003eCANTAM 3 EPI\u0026nbsp;\u003c/strong\u003eproject which was reviewed and approved by National Ethic Committee for research (\u003cstrong\u003ePROT N027/2022/CNE/SG-P\u003c/strong\u003e). Written informed consent was obtained from all participants before their inclusion in the study. Parents or legal guardians signed on behalf of adolescents their gave their assent. All procedures were conducted in accordance with the ethical guidelines of Helsinki declaration. Malaria diagnosis was free, and infected patients were treated with artemisinin-based combination therapies (ACT).\u0026nbsp;\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003e\u003cstrong\u003e\u003cem\u003eData analysis \u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eData were double entered into Excel Microsoft sheet and analysed using R software. Descriptive analysis were conducted to summarise the characteristics of the study population. The prevalence of asymptomatic malaria was determined. Differences in prevalence and parasitaemia levels between urban and rural areas were assessed using Chi-Square Test for categorical variables and Kruskal-Wallis Test or ManWithney Test for continuous variables. Bivariate and multivariate logistic regression analyses were performed to investigate the association with sociodemographic factors and ITN use (independent variables) and asymptomatic microscopic \u003cem\u003ePlasmodium\u003c/em\u003e infection (dependant variable). In order to control for confounders, the independent variables found associated with the dependant variable in the bivariate analysis with a \u003cem\u003ep\u003c/em\u003e-value below 0.20 were used for the multivariate logistic regression analysis. Crude (cOR) or adjusted (aOR) odds ratio were presented together with their 95% confidence intervals (95% CI). A significance level of p\u0026lt;0.05 was considered statistically significant. \u0026nbsp;\u003c/p\u003e"},{"header":"RESULTS","content":"\u003cul\u003e\n \u003cli\u003e\u003cstrong\u003e\u003cem\u003eCharacteristics of study participants\u003c/em\u003e\u003c/strong\u003e\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eA total of 1496 participants were enrolled in this study, 965 (64.5%) in rural and 531 (35.5%) in urban sites. Women predominated; the sex ratio was 0.6. The participant median age was 44 [32-56] years, 42.6% (n= 638/1496) were aged under 55 years. ITNs use was mostly infrequent (Tableau I). Hb levels could be measured in 824 participants, the frequency of anaemia was 22.7% (n=187/824). The median Hb level was 12.3[11.0-13.3] g/dL without difference between rural (12.0[10.6-14.0] g/dL and urban (12.4[11.3-13.4] g/dL) communities (p=0.24). Among the 187 anaemic individuals 55.1% (n=103) had moderate anaemia.\u0026nbsp;\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003e\u003cstrong\u003e\u003cem\u003ePrevalence of asymptomatic malaria\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eOverall, 238 (15.3%) participants had microscopically confirmed \u003cem\u003ePlasmodium\u003c/em\u003e asymptomatic infection. \u003cem\u003eP. falciparum\u003c/em\u003e was the only species identified. Malaria prevalence was significantly higher in rural compared to urban sites (\u003cem\u003ep\u0026lt;0.01\u003c/em\u003e) (Table 2). Regarding parasite density, it was 20[14-30] p/\u0026micro;L in participants with a positive blood smear. The majority (95.4%; n=206/216) of those living in Bitam had parasitaemia above 100/\u0026micro;L, whereas for those from Libreville and Owendo (68.2%; n=15/22) it was more often below 100p/\u0026micro;L (\u003cem\u003ep\u0026lt;0.01\u003c/em\u003e).\u0026nbsp;\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003e\u003cstrong\u003e\u003cem\u003eAsymptomatic malaria and sociodemographic factors\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eLast level of school attended was significantly associated with \u003cem\u003eP. falciparum\u003c/em\u003e infection, individuals with primary or secondary school level having the highest prevalences and median parasite densities (p\u0026lt;0.01) (Table II). A trend towards higher prevalence and parasitaemia wad also observed in men and individuals over 55 years of age (Table II).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eBivariate analysis showed that none, primary or secondary school level, being worker or unemployed, residing in rural area were significantly associated with higher odds of asymptomatic malaria (Table II).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe multivariate logistic regression analysis confirmed that education, residing area, professional status were risks factors for \u003cem\u003eP. falciparum\u003c/em\u003e asymptomatic infection in the study population. Compared to urban community, rural inhabitants had seven times (aOR:7.1[4.4-9.8]; p\u0026lt;0.01) higher risk of asymptomatic malaria. The risk of malaria was 5 times higher in workers compared to unemployed participants (aOR: 5.2[3.4-7.8]; p\u0026lt;0.01). It was more than 2 times higher in people with primary school or secondary school (aOR: 2.6[1.6-4.0]; p\u0026lt;0.01).\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003e\u003cstrong\u003e\u003cem\u003eAsymptomatic malaria prevalence according to ITNs use and Hb level\u003c/em\u003e\u003c/strong\u003e\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eNo significant difference was observed between ITN users and non-users (Table II). The median Hb level was 12.3[11.0-14.0] g/dL in participants with a positive blood smear and 12.3 [11.0-13.6] g/dL in the uninfected ones (p=0.69). Similarly, the rate of anaemic participants was comparable in the presence (21.8%; n=24/110) or in the absence (22.8%; n=163/715) of \u003cem\u003ePlasmodium\u003c/em\u003e parasitaemia (p=0.92). There was no difference in parasite density between anaemic and non-anaemic participants (p=0.78).\u0026nbsp;\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003e\u003cstrong\u003eComparison between rural and urban communities\u003c/strong\u003e\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eThe association between the socio-demographics factors, ITN use, and the rate of positive blood smear was assessed according to the residence area, revealing different risk factors. In urban community, only being unemployed was identified as a significant risk factor for asymptomatic malaria (Table III). This association remained significant after the multivariate logistic regression (aOR:3.4 IC95%: [1.1-7.1]; \u003cem\u003ep=0.03\u003c/em\u003e)\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAmong inhabitants from Bitam, the rural city, the unemployed ones had the lowest rate of \u003cem\u003eP. falciparum\u003c/em\u003e infection. Whereas having attended any school level was predictor of the disease, in bivariate and in multivariate analysis (primary school: aOR:5.0 IC95% [2.0-8.3]; secondary school: aOR: 5.0 IC95% [2.4-9.0]; university: aOR:5.0 IC95% [1.3-11.2]) compared to those who had never attended school (\u003cem\u003ep\u0026lt;0.01\u003c/em\u003e). (Table III)\u003c/p\u003e\n\u003cp\u003eRegarding the professional status, managers were at lower risk of contracting asymptomatic malaria, with being worker at 1.8 times (aOR:1.8 IC95% [0.96-4.2]; \u003cem\u003ep=0.05\u003c/em\u003e) at higher risk of presenting with asymptomatic malaria during the study period (Table III).\u003c/p\u003e\n\u003cp\u003eITN use and age were no longer found significantly associated with malaria when taking account the confounders, in the multivariate analysis either in urban or in rural settings.\u003c/p\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eAlmost 20 years after implementation of ITN, IPTp-SP and ACT in Gabon, malaria transmission remains high across the country. Data from rural and semi-urban areas report a resurgence of symptomatic malaria cases, which started prior to the COVID-19 pandemic [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] and increase thereafter. There are several challenges towards elimination of malaria, including low coverage of preventive measures, poor access to healthcare, drug and insecticide resistance, population and vector behaviors, the maintenance of parasite reservoir [\u003cspan additionalcitationids=\"CR14\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. This study highlighted a substantial burden of asymptomatic malaria (15.9%) in adults from three communities in Gabon. This prevalence is similar to that reported in a study performed in 2013 in different settlements in Gabon (18.8%) as well as in Uganda (15.4%) in 2020 [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Other authors report higher prevalences in Cameroon (38.4%) and Kenya (42%) [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. This difference could be attributed to the methodology used in the different studies, the study population, and the ecology of sites, as well as the level of malaria endemicity in the different study areas. The prevalence in the urban community was 4.1% slightly lower to that reported in 2019 at Owendo (5.9%) [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Urban environments after improved housing infrastructing such as sealed wells and screened windows. Urban dwellers have probably better knowledge of malaria risk and prevention. All these factors, including fewer suitable mosquitoes breeding sites, reduce exposure to the vectors. The higher prevalence of asymptomatic malaria observed in Libreville and Owendo, compared to the rural city of Bitam is consistent with findings across others sub-Saharan Africa. Rural residents were thus more than six times more likely to harbor asymptomatic infection, underscoring a persistent local transmission intensity.\u003c/p\u003e\u003cp\u003eIndeed, urban environments are less favorable to vector species, particularly \u003cem\u003eAn. gambiae\u003c/em\u003e, which has a strong preference for clean water. Actually, the increasing insalubrity and polluted water in the greater Libreville area are leading cause of reduction in the Anopheles population. Considering that malaria diagnosis was performed using only microscopic techniques, the prevalence of asymptomatic carriage is very likely underestimated. A recent metanalysis reported that the prevalence of asymptomatic malaria among older children in Central Africa is approximately 30% [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Adults therefore represent a significant parasite reservoir in Libreville, most likely due to low ITN usage (19%) and more frequent exposure to mosquito bites compared to children. These findings highlight the need to raise awareness among this age group regarding malaria prevention, and to include them alongside young children and pregnant women in health education campaigns and mass ITN distribution programs.\u003c/p\u003e\u003cp\u003eIn rural areas, conditions are favorable to exposure to mosquito bites, so repeated exposure to the bites of infectious mosquitoes carrying malaria parasites makes the host's immune system better able to control parasite density, thus preventing the onset of clinical symptoms [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. A study carried out in 2008 in several rural villages in Gabon reported an estimated overall prevalence of 6.2%, rising to 37.2% [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Although malaria transmission in Gabon, an heterogenicity of endemicity level is observed. Bitam is a hyperendemic zone, with much more vegetation, and the villages surveyed were close to forested areas, a propitious environment for vector multiplication. Indeed, environmental factors such as proximity to forest, household density and altitude tend to be significantly and positively correlated with malaria risk [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. The high prevalence of asymptomatic malaria in rural areas could be due to exposure-related immunity, which occurs when people frequently exposed to parasites eventually develop premunition [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eSociodemographic factors were independently and differentially associated with asymptomatic malaria carriage in urban and rural communities. Men appeared more frequently infected than women, as previously reported by Kumari et al. in India [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. This observation likely reflects gender-specific behavioural patterns. While women generally remain at home after work and during the night, men are more likely to engage in late-afternoon or overnight professional and social activities. In urban settings, they often stay outdoors beyond working hours, whereas in rural areas, they may spend the night in the forest for hunting or agricultural activities, or gather with other men in the \u0026ldquo;corps de garde\u0026rdquo; to socialise late into the night. These behaviours increase their exposure to mosquito bites.\u003c/p\u003e\u003cp\u003eOccupational exposure appears to play a key role in the higher risk of asymptomatic malaria among rural male workers. Bitam, a forested area, is particularly prone to transmission, and overnight stays in the forest for hunting or farming, some well-established risk factors [24;18;8].\u003c/p\u003e\u003cp\u003eAdditionally, specific occupations such as farming, hunting, guarding, housework, and studying were associated with increased asymptomatic carriage [25, 26. Interestingly, most unemployed individuals in urban settings were students, whereas in rural Bitam, the unemployed were mainly engaged in informal subsistence activities, including farming or hunting, often in the forested or in farm/bush around their house, thus, further increasing their exposure risk. Of particular note, individuals with secondary or university education, especially retirees who have returned to settle in villages, were frequently involved in managing their own plantations. These educated individuals often live off the proceeds of their agricultural production and spend long hours working outdoors. This could partly explain the unexpectedly higher prevalence of asymptomatic carriage among those with higher education levels compared to middle managers.\u003c/p\u003e\u003cp\u003eThese findings underline the importance of adapting malaria control strategies to behavioural and occupational contexts. Indeed, encouraging workplace intervention and the use of long-sleeved shirts and trousers during outdoor and forest-based activities, especially among men and farmers. Then, promoting ITN distribution and communication campaigns which specifically target adult men and older individuals, not just children and pregnant women. Moreover, tailoring health education to rural retirees and educated populations regarding the continued risk of malaria for retired individuals engaging in agricultural work, even if they consider themselves knowledgeable and community engagement in behavioural by Integrating malaria prevention into rural development schemes should be considered key interventions for malaria control in rural settings. [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eDespite global efforts to promote the use of insecticide-treated nets (ITNs), the lack of protective effect against malaria may be attributable to suboptimal coverage (below 35%), improper usage, or the emergence of insecticide resistance, factors that warrant further investigation. A study conducted in Nigeria similarly found no significant association between ITN use and asymptomatic \u003cem\u003ePlasmodium falciparum\u003c/em\u003e carriage [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. In contrast, evidence from Cameroon and across sub-Saharan Africa suggests that not sleeping under an ITN or using it improperly is associated with at least a 3.5-fold increased risk of asymptomatic malaria [8; 30]. The interview did not investigate the condition of the net or the duration and frequency of use. Long-acting insecticide-impregnated nets (LLIN) provide both chemical and physical barriers against mosquitoes by reducing their contact with humans, however when damaged they become less effective against mosquito bites. Also, owning an LLIN is not always synonymous with good use, as the appropriate use of LLINs is one of the main cost-effective interventions for malaria prevention [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Although LLINs are considered an effective means of avoiding mosquito bites, their improper use and longevity could lead to the loss of their effectiveness and therefore LLINs no longer offer effective protection against malaria-vector mosquitoes [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. In addition, the last net distribution campaigns in this region were more than three years ago, and with the occurrence of the COVID 19 pandemic, efforts were concentrated on the epidemic response. Despite some inconsistent findings, ITN use remains an effective strategy for preventing both asymptomatic and symptomatic malaria. Its promotion and the achievement of universal coverage should remain key local targets in efforts to move towards malaria elimination. Moreover, Strengthening community education on correct net use and exploring alternative vector control strategies are essential to enhance the overall effectiveness of malaria prevention interventions.\u003c/p\u003e\u003cp\u003eParasitemia levels were higher in rural areas than in urban areas, which may be explained by the fact that due to their greater exposure to infective mosquito bites than those living in urban areas and their acquired premunition, people living in rural areas are better able to withstand parasite densities. In addition, this anti-parasite immunity and premunition can help control parasite multiplication, thereby reducing parasite loads in adults. In a study conducted is Ashanti region of Ghana, participants living in urban areas had lower prevalence and parasite densities compared those residing in rural prevalence and peri urban settings [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. In our local context, parasitemia were also lower than those typically reported among symptomatic patients in Gabon [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Chronic carriage with low or submicroscopic parasite densities contributes to the persistence of malaria transmission through these silent reservoirs. Moreover, a non-negligible proportion of these individuals may eventually develop symptomatic and life-threatening symptomatic diseases.\u003c/p\u003e\u003cp\u003eThis study has some limitations. The prevalence of asymptomatic plasmodial infection in this study may have been underestimated, as only microscopy was used for the diagnosis. Patients with submicroscopic infections may have been classified as negative, leading to an underestimation of the true prevalence of asymptomatic malaria. The convenience sampling may limit the generalizability and self-reporting of ITN use may introduce reporting bias. Nevertheless, this study is among the few to assess asymptomatic microscopic \u003cem\u003ePlasmodium\u003c/em\u003e carriage in non-pregnant adults in endemic Central Africa. The large sample size and inclusion in both urban and rural settings strengthen the validity of our data that highlight important intervention gaps. Targeted strategies for adults\u0026rsquo; populations including manual laborers and the unemployed as well as introduction of community-wide screening using ultra-sensitive RDT or molecular tools are importantly necessary.\u003c/p\u003e"},{"header":"CONCLUSION","content":"\u003cp\u003eA Gabon facies a resurgence in malaria incidence the present findings highlight the dual challenge of low adult targeted, ITN and other preventive measures coverage and rural, urban disparities in asymptomatic \u003cem\u003ePlasmodium falciparum\u003c/em\u003e carriage. National control strategies must expand beyond clinical case management to include active surveillance and adult focused prevention to accelerate progress toward malaria control and elimination.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003e\u003cem\u003eP.falciparum\u0026nbsp; \u0026nbsp; \u0026nbsp;Plasmodium falciparum\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eITN\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;Insecticide-treated nets\u003c/p\u003e\n\u003cp\u003eaOR\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;adjusted odds ratio\u003c/p\u003e\n\u003cp\u003ecOR\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;crude odds ratio\u003c/p\u003e\n\u003cp\u003eACT\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Artemisinin-based combination therapies\u003c/p\u003e\n\u003cp\u003eIPTp-SP \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Intermittent prevention treatment Sulfadoxine-Pyrimethamine\u003c/p\u003e\n\u003cp\u003eHb\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;Haemoglobin\u003c/p\u003e\n\u003cp\u003eRDT\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Rapid diagnostic test\u003c/p\u003e\n\u003cp\u003eIC \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Intervale Confidence\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe would like to thank the participants and all team from the Department of Parasitology-Mycology.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMBDC: conceptualized the study, conducted and acquisitions of data, interpreted analysis and wrote the first draft, edited the manuscript; NPM, JMNN, HNK, MAM, LNA and RM: data and sample collection, and performed microscopy; NPM and LNA: data analysis; DAMM and CJM: reported data on excel Microsoft sheet; BAMK: conceptualized and supervised the study, interpreted data and corrected the manuscript; DPMM: coordinated the microscopy analysis and revision the manuscript\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAll authors reviewed and approved the final draft of the manuscript.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was a part of CANTAM-EPI 3\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datatests used and analysed in this study are available from the corresponding author.\u0026nbsp;\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\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eWHO. World Malaria Report 2024. Geneva: World Health Organization; 2024.\u003c/li\u003e\n\u003cli\u003eMawili-Mboumba DP, Bouyou Akotet MK, Kendjo E, Nzamba J, Medang MO, Mbina JR, et \u003cem\u003eal\u003c/em\u003e. Increase in malaria prevalence and age of at risk population in different areas of Gabon. \u003cem\u003eMalar J\u003c/em\u003e. 2013 Jan 2;12:3. doi: 10.1186/1475-2875-12-3. \u003c/li\u003e\n\u003cli\u003eAssele V, Ndoh GE, Nkoghe D, Fandeur T. No evidence of decline in malaria burden from 2006 to 2013 in a rural Province of Gabon: implications for public health policy. 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Malaria prevalence, risk factors and spatial distribution in a hilly forest area of Bangladesh. PLoS One. 2011 Apr 21;6(4):e18908. doi: 10.1371/journal.pone.0018908. \u003c/li\u003e\n\u003cli\u003eLaishram DD, Sutton PL, Nanda N, Sharma VL, Sobti RC, Carlton JM, et \u003cem\u003eal\u003c/em\u003e. The complexities of malaria disease manifestations with a focus on asymptomatic malaria. \u003cem\u003eMalar J\u003c/em\u003e. 2012 Jan 31;11:29. doi: 10.1186/1475-2875-11-29. \u003c/li\u003e\n\u003cli\u003eKar NP, Kumar A, Singh OP, Carlton JM, Nanda N. A review of malaria transmission dynamics in forest ecosystems. \u003cem\u003eParasites Vectors.\u003c/em\u003e 20147 ; 265. https://doi.org/10.1186/1756-3305-7-265\u003c/li\u003e\n\u003cli\u003eMbah CE, Ambe LA, Ngwewondo A, Kidzeru EB, Akwah L, Mountchissi C, et al. 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Factors associated with contracting border malaria: A systematic and meta-analysis. \u003cem\u003ePloS One\u003c/em\u003e. 2025 Jan 3;20(1):e0310063\u003c/li\u003e\n\u003cli\u003eOnyiah AP, Ajayi IO, Dada-Adegbola HO, Adedokun BO, Balogun MS, Nguku PM, et al. (2018) Long-lasting insecticidal net use and asymptomatic malaria parasitaemia among household members of laboratory-confirmed malaria patients attending selected health facilities in Abuja, Nigeria, 2016: A cross-sectional survey. PLoS ONE 13(9): e0203686. https://doi.org/10.1371/journal.pone.0203686\u003c/li\u003e\n\u003cli\u003eIbrahim AO, Agbesanwa TA, Aremu SK, Bello IS, Elegbede OT, Gabriel-Alayode OE, et \u003cem\u003eal.\u003c/em\u003e Malaria infection and its association with socio-demographics, long lasting insecticide nets usage and hematological parameters among adolescent patients in rural Southwestern Nigeria. PLoS ONE. 2023 ;18(7): e0287723. https://doi.org/10.1371/journal.pone.0287723\u003c/li\u003e\n\u003cli\u003eNgongang-Yipmo ES, Tchouakui M, Menze BD, Mugenzi LMJ, Njiokou F, Wondji CS. Reduced performance of community bednets against pyrethroid-resistant Anopheles funestus and Anopheles gambiae, major malaria vectors in Cameroon. Parasit Vectors. 2022 Jun 26;15(1):230. doi: 10.1186/s13071-022-05335-2.\u003c/li\u003e\n\u003cli\u003eHayuma PM, Wang CW, Liheluka E, Baraka V, Madebe RA, Minja DTR, et \u003cem\u003eal\u003c/em\u003e. Prevalence of asymptomatic malaria, submicroscopic parasitaemia and anaemia in Korogwe District, north-eastern Tanzania. \u003cem\u003eMalar J\u003c/em\u003e. 2021 Oct 29;20(1):424. doi: 10.1186/s12936-021-03952-3\u003c/li\u003e\n\u003cli\u003eMutala AH, Badu K, Owusu C, Agordzo SK, Tweneboah A, Abbas DA, et \u003cem\u003eal\u003c/em\u003e. Impact of malaria on haematological parameters of urban, peri-urban and rural residents in the Ashanti region of Ghana: a cross-sectional study. \u003cem\u003eAAS Open Res\u003c/em\u003e. 2020 Jul 9;2:27. doi: 10.12688/aasopenres.12979.3. \u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTables 1 to 3 are available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"malaria-journal","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"malj","sideBox":"Learn more about [Malaria Journal](http://malariajournal.biomedcentral.com/)","snPcode":"12936","submissionUrl":"https://submission.nature.com/new-submission/12936/3","title":"Malaria Journal","twitterHandle":"@malariajournal","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Asymptomatic malaria, Plasmodium falciparum, adults, rural–urban disparity, Gabon","lastPublishedDoi":"10.21203/rs.3.rs-7052550/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7052550/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground:\u003c/strong\u003e\u003cbr\u003e\nAsymptomatic malaria represents a major challenge for malaria control and elimination efforts, particularly in endemic regions such as Gabon, where adult reservoirs are under-investigated. This study aimed to assess the burden and determinants of asymptomatic \u003cem\u003ePlasmodium falciparum\u003c/em\u003e infection among adults in urban and rural communities in Gabon.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods:\u003c/strong\u003e\u003cbr\u003e\nA community-based cross-sectional survey was conducted between January and December 2023 in Bitam (rural), Libreville, and Owendo (urban). Adults aged ≥18 years with no malaria symptoms or recent antimalarial treatment were included. Demographic, socio-economic, and ITN-use data were collected via structured questionnaire. Malaria was diagnosed by microscopy. Logistic regression models were used to identify factors associated with asymptomatic infection.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults:\u003c/strong\u003e\u003cbr\u003e\nAmong 1,496 participants, the overall prevalence of asymptomatic \u003cem\u003eP. falciparum\u003c/em\u003e infection was 15.3%, significantly higher in rural areas (22.4%) than in urban settings (4.1%; p\u0026lt;0.01). Parasite densities were also higher in rural participants. Independent risk factors included rural residence (aOR: 7.1; 95% CI: [4.4–9.8]), being a worker (aOR: 5.2; 95% CI: [3.4–7.8]), and having primary or secondary education (aOR: 2.6; 95% CI: [1.6–4.0]). ITN use was low (32.7%) and not significantly protective in multivariate analysis.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion:\u003c/strong\u003e\u003cbr\u003e\nThe substantial burden of asymptomatic malaria in adults, particularly in rural Gabon, underscores the need to broaden malaria control strategies. These interventions must be tailored to adult populations, considering occupational exposure and local transmission dynamics. Expanding screening and improving ITN access and use are critical to reduce the hidden reservoir and achieve malaria elimination.\u003c/p\u003e","manuscriptTitle":"Burden and determinants of asymptomatic malaria among adults living in urban and rural areas in Gabon in 2023: a community-based cross-sectional study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-16 11:58:03","doi":"10.21203/rs.3.rs-7052550/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-08-06T16:20:40+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-05T19:23:15+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-04T19:56:46+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"190877056139610872540787196029226604037","date":"2025-08-04T18:38:17+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"16216571751745720996471613501950572655","date":"2025-07-24T20:09:05+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-07-14T15:08:58+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-07-07T17:45:59+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-07-07T17:45:06+00:00","index":"","fulltext":""},{"type":"submitted","content":"Malaria Journal","date":"2025-07-05T10:38:23+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"malaria-journal","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"malj","sideBox":"Learn more about [Malaria Journal](http://malariajournal.biomedcentral.com/)","snPcode":"12936","submissionUrl":"https://submission.nature.com/new-submission/12936/3","title":"Malaria Journal","twitterHandle":"@malariajournal","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"525689d1-aa12-4852-90c6-47390b0160a1","owner":[],"postedDate":"July 16th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-12-29T16:03:37+00:00","versionOfRecord":{"articleIdentity":"rs-7052550","link":"https://doi.org/10.1186/s12936-025-05672-4","journal":{"identity":"malaria-journal","isVorOnly":false,"title":"Malaria Journal"},"publishedOn":"2025-12-24 15:58:29","publishedOnDateReadable":"December 24th, 2025"},"versionCreatedAt":"2025-07-16 11:58:03","video":"","vorDoi":"10.1186/s12936-025-05672-4","vorDoiUrl":"https://doi.org/10.1186/s12936-025-05672-4","workflowStages":[]},"version":"v1","identity":"rs-7052550","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7052550","identity":"rs-7052550","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}