Impact of Mass Drug Administration with Ivermectin, Diethylcarbamazine, and Albendazole in Elimination of Lymphatic Filariasis in Five Districts of Nepal

Background Nepal aims to eliminate Lymphatic Filariasis (LF) by 2030. Mass drug administration (MDA) has ceased in 53 of 64 endemic districts. In 2023, five districts with persistent LF (≥2% antigen prevalence) completed two rounds of MDA using a three-drug regimen (Ivermectin, Diethylcarbamazine, and Albendazole; IDA), achieving over 65% coverage. An Epidemiological Monitoring Survey (EMS) was conducted to evaluate IDA’s impact.

A cross-sectional EMS was conducted 9 months post-MDA in 11 evaluation units (EUs) across five districts, using two sites per EU (n=22). A total of 6,829 individuals aged ≥20 years were sampled via multi-stage methods, with ≥300 blood samples per site. Data on demographics and MDA participation were collected. LF antigen testing was followed by night blood microfilariae testing in antigen-positive samples. Analysis included non-parametric tests, logistic and mixed-effects models accounting for site-level clustering, and penalized regression (lasso and ridge) to assess predictor importance and manage multicollinearity.

Nine of 11 EUs passed EMS. Two EUs in Kapilvastu failed due to ≥1% microfilariae prevalence in at least one site. Microfilariae prevalence was negatively correlated with site MDA coverage (p = 0.04), but not antigen prevalence (p = 0.8). Overall, 4.63% of participants were antigen-positive and 0.34% were microfilariae-positive (ratio 14:1). Being female (OR 0.12; 95% CI: 0.04–0.36) and participation in latest MDA round (OR 0.34; 95% CI: 0.15–0.77) were associated with lower microfilariae prevalence.

Nine EUs met the EMS threshold for impact assessment eligibility. Female gender and participation in the most recent MDA round were protective against microfilariae. Targeted MDA strategies focusing on men and high-risk areas are recommended. Competing Interest Statement The authors have declared no competing interest. Funding Statement It was supported by American People through the United States Agency for International Development (USAID), Act to End NTDs | East, and RTI International in partnership with The Carter Center, Fred Hollows Foundation, Light for the World, Sightsavers, Results for Development, Save the Children, and WI-HER under cooperative agreement No. 7200AA18CA00040 and do not reflect the views of USAID or the United States Government. DTSH is funded by the Percival Carmine Chair in Epidemiology & Public Health. Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: This survey was carried out by EDCD and VBDRTC both institutions are the major implementing bodies for management of vector borne diseases under Nepal’s Ministry of Health and Population (MoHP). The activities conducted by MoHP as a part of the set strategic goals for the regular monitoring and programmatic progress in National Lymphatic Filariasis Elimination Program (NLFE) have been exempted by Nepal Health Research Council (NHRC) from the ethical review process (Ref. no 1530 NHRC, December 10, 2020). Nevertheless, written informed consent was obtained from all the participants prior to interviews and blood sample collection. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Data Availability All Data are presented in the paper and if raw data are required, it is available upon request!