Assessment of antigenemia among children in four hotspots of filarial endemic districts of Nepal during post-MDA surveillance

Abstract

Background: Sixty-three out of 77 districts reported lymphatic filariasis (LF) endemic in Nepal. Mass drug administration (MDA) with diethylcarbamazine (DEC) and albendazole (ALB) treatment program was continued for 6 to 11 rounds in these districts. Nepal government has stopped the MDA program based on the transmission assessment survey (TAS) report of 2014 and 2018 indicating Wuchereria bancrofti antigenemia prevalence < 2%. But the persistence of low levels of the circulating filarial antigen (CFA) in some foci of four endemic districts of Central Nepal, i.e., 0.4% in Dhading, 0.7% in Mahottari, 0.21% in Lalitpur and 1.2% in Bara district could responsible for enhancing the risk of infection resurgence. Hence the present study was designed to assess antigenic prevalence using Filariasis Test Strip (Alere, Scarborough ME) in children born after MDA in hotspot areas of four endemic districts of Central Nepal. Results: The present study covers 70% children of the eligible population. The result revealed significantly high CFA prevalence in hotspots of Mahottari district belonging to the Terai region and Dhading district belonging to the hilly region, i.e., 13% and 10%, respectively, compared to baseline prevalence and TAS report. While in Lalitpur district and Bara district CFA prevalence was still found to be less than 2%. A higher number of MDA rounds covered in hotspots were found significantly associated with the low antigenic prevalence of W. bancrofti. Whereas median treatment coverage and inter-quartile range (IQR) in study districts were not found significantly associated with CFA prevalence. Although the clinical manifestation of hydrocele (1%) was found in all four study districts, it was not due to the W. bancrofti infection. Conclusions: Two hotspot regions, one each from the Terai (Mahottari) and hilly (Dhading) districts were found highly prevalent with CFA and significantly associated with the number of MDA rounds but were not associated with treatment coverage and IQR. Higher CFA prevalence was observed in hotspots where baseline prevalence was high together indicating that rounds of MDA program need to be extended further in these hotspot regions of endemic districts.