Longitudinal entomological study using molecular xenomonitoring of Wuchereria bancrofti in Culex quinquefasciatus in three Nepalese districts: Implications for lymphatic filariasis transmission assessment and elimination
- 1Center for Health and Disease Studies, Kathmandu, Nepal
Abstract
BackgroundIn Nepal, lymphatic filariasis (LF), caused by Wuchereria bancrofti, remains a priority neglected tropical disease targeted for elimination by 2030. Despite large-scale mass drug administration (MDA) and post-MDA surveillance, focal transmission may persist. Molecular xenomonitoring (MX) of mosquito vectors is a complementary method for detecting ongoing transmission. This study assessed mosquito abundance and species composition and compared gravid traps and CDC light traps for capturing Culex quinquefasciatus, the primary LF vector. It examined spatial and seasonal vector patterns, W. bancrofti infection rates, and climatic associations across three LF endemic districts.
MethodologyA longitudinal entomological survey was conducted from September 2022 to September 2023 in selected sites of Dhading, Jhapa, and Kapilvastu districts using gravid traps and CDC light traps. Mosquitoes were morphologically identified to species level, and female Cx. quinquefasciatus were pooled (up to 25 mosquitoes) for detection of W. bancrofti DNA using real-time PCR. Mosquito abundance, species composition, trap efficiency, spatial variation (within and between locations), temporal trends (daily, weekly, monthly, seasonal), infection rate (pool positivity, and maximum likelihood estimate (MLE) of infection using PoolTestR package in R software), and climatic associations (precipitation, temperature, humidity) were analysed.
ResultsA total of 60,922 mosquitoes belonging to eight genera (Culex, Anopheles, Aedes, Armigeres, Malaya, Mansonia, Tripteroides, and Toxorhynchites) were identified. Of these, 16,044 were female Cx. quinquefasciatus. Gravid traps showed higher relative trapping efficiency of female Cx. quinquefasciatus than light traps, with the highest efficiency observed in Jhapa (3.60:1). Temporal trends varied across locations; however, overall Cx. quinquefasciatus abundance peaked during the spring and summer months (March-May), coinciding with the monsoon period, and was positively correlated with climatic factors. W. bancrofti infection rates varied by location and trap type, with gravid traps yielding higher infection rates, particularly in Jhapa. A total of 785 pools of Cx. quinquefasciatus were screened. Pool positivity and infection prevalence (MLE) ranged from 10.3% to 17.6% and 0.5% to 0.9% in Dhading, 12.5% to 36.8% and 0.9% to 2.0% in Jhapa, and 5.3% to 20.0% and 0.3% to 1.5% in Kapilvastu, respectively.
ConclusionsThe study highlights ongoing transmission in three LF-endemic areas of Nepal, emphasising the need for continued surveillance in high-risk areas and periods. Gravid trap-based xenomonitoring could complement community-based W. bancrofti surveillance by identifying hotspots and optimising the timing and targeting of LF elimination interventions.
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BibTeX
@misc{shrestha2026longitudinal,
title = {{Longitudinal entomological study using molecular xenomonitoring of Wuchereria bancrofti in Culex quinquefasciatus in three Nepalese districts: Implications for lymphatic filariasis transmission assessment and elimination}},
author = {D. Shrestha and B. Bajracharya and P. Shah and P. Shrestha and S. Ghimire and S. R. Paudel and S. Dangol and P. Shrestha and S. Rajbanshi and P. Ranjitkar and S. Chand and M. Sharma and C. K. Sardar and R. Tuladhar and S. Bajracharya and A. K. Karna and K. D. Manandhar and R. K. Mahato and G. Dahal and T. Williams and L. A. Kelly-Hope},
howpublished = {medRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.23.26366133},
url = {https://www.medrxiv.org/content/10.64898/2026.10.23.26366133v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Longitudinal entomological study using molecular xenomonitoring of Wuchereria bancrofti in Culex quinquefasciatus in three Nepalese districts: Implications for lymphatic filariasis transmission assessment and elimination
AU - D. Shrestha
AU - B. Bajracharya
AU - P. Shah
AU - P. Shrestha
AU - S. Ghimire
AU - S. R. Paudel
AU - S. Dangol
AU - P. Shrestha
AU - S. Rajbanshi
AU - P. Ranjitkar
AU - S. Chand
AU - M. Sharma
AU - C. K. Sardar
AU - R. Tuladhar
AU - S. Bajracharya
AU - A. K. Karna
AU - K. D. Manandhar
AU - R. K. Mahato
AU - G. Dahal
AU - T. Williams
AU - L. A. Kelly-Hope
PY - 2026
DA - 2026/10/23
PB - medRxiv
DO - 10.64898/2026.10.23.26366133
UR - https://www.medrxiv.org/content/10.64898/2026.10.23.26366133v1
AB - BackgroundIn Nepal, lymphatic filariasis (LF), caused by Wuchereria bancrofti, remains a priority neglected tropical disease targeted for elimination by 2030. Despite large-scale mass drug administration (MDA) and post-MDA surveillance, focal transmission may persist. Molecular xenomonitoring (MX) of mosquito vectors is a complementary method for detecting ongoing transmission. This study assessed mosquito abundance and species composition and compared gravid traps and CDC light traps for capturing Culex quinquefasciatus, the primary LF vector. It examined spatial and seasonal vector patterns, W. bancrofti infection rates, and climatic associations across three LF endemic districts. MethodologyA longitudinal entomological survey was conducted from September 2022 to September 2023 in selected sites of Dhading, Jhapa, and Kapilvastu districts using gravid traps and CDC light traps. Mosquitoes were morphologically identified to species level, and female Cx. quinquefasciatus were pooled (up to 25 mosquitoes) for detection of W. bancrofti DNA using real-time PCR. Mosquito abundance, species composition, trap efficiency, spatial variation (within and between locations), temporal trends (daily, weekly, monthly, seasonal), infection rate (pool positivity, and maximum likelihood estimate (MLE) of infection using PoolTestR package in R software), and climatic associations (precipitation, temperature, humidity) were analysed. ResultsA total of 60,922 mosquitoes belonging to eight genera (Culex, Anopheles, Aedes, Armigeres, Malaya, Mansonia, Tripteroides, and Toxorhynchites) were identified. Of these, 16,044 were female Cx. quinquefasciatus. Gravid traps showed higher relative trapping efficiency of female Cx. quinquefasciatus than light traps, with the highest efficiency observed in Jhapa (3.60:1). Temporal trends varied across locations; however, overall Cx. quinquefasciatus abundance peaked during the spring and summer months (March-May), coinciding with the monsoon period, and was positively correlated with climatic factors. W. bancrofti infection rates varied by location and trap type, with gravid traps yielding higher infection rates, particularly in Jhapa. A total of 785 pools of Cx. quinquefasciatus were screened. Pool positivity and infection prevalence (MLE) ranged from 10.3% to 17.6% and 0.5% to 0.9% in Dhading, 12.5% to 36.8% and 0.9% to 2.0% in Jhapa, and 5.3% to 20.0% and 0.3% to 1.5% in Kapilvastu, respectively. ConclusionsThe study highlights ongoing transmission in three LF-endemic areas of Nepal, emphasising the need for continued surveillance in high-risk areas and periods. Gravid trap-based xenomonitoring could complement community-based W. bancrofti surveillance by identifying hotspots and optimising the timing and targeting of LF elimination interventions.
ER -