MOLECULAR XENOMONITORING OF LYMPHATIC FILARIASIS ELIMINATION IN A SENTINEL VILLAGE IN MENOUFYIA GOVERNORATE, EGYPT

Abstract

Lymphatic filariasis is a neglected tropical disease caused by infection with the mosquito-borne, thread-like, parasitic filarial worms Wuchereria bancrofti, Brugia malayi and B. timori. It is estimated that more than one billion people worldwide live in endemic areas, and that more than one third of these are in Sub-Saharan Africa. Bancroftian Filariasis is focally endemic in Egypt where the mosquito vector responsible for its transmission is female Culex pipiens. The Global Program to Eliminate Lymphatic Filariasis (GPELF) has the ambitious goal of eliminating LF in all disease-endemic areas by the year 2020. In 2000, Egypt was one of the first countries to join the global efforts when the Ministry of Health and Population (MOHP) initiated a National Program for Elimination of Lymphatic Filariasis (NPELF) based on the WHO strategy. Diagnostic tools are important to GPELF because they affect decisions regarding where to distribute MDA, how to measure its effects, how to define targets and endpoints for stopping MDA and how to monitor populations for resurgence of LF transmission following suspension of MDA. Assessing infection in humans can be considered a "lagging indicator" because the prepatent period may extend for months after infection. In addition, reluctance of some human populations to submit to regular blood examinations could affect the assessment results, Therefore assessment of infection in vectors offers advantages for the monitoring of infection providing "real-time" estimates of filarial transmission as the ultimate test of interruption of transmission rests on infectivity rates of the mosquito vectors. The study included two cross-sectional surveys were conducted in Kafr El- Tarainah and Samalay villages, Ashmoun district, Menoufyia Governorate, Egypt in 2014. The purpose of the study was to investigate the impact of implementation of the 13th round of MDA following detection of newly infected cases by the ICT and thick blood film examination in two Egyptian villages in Menoufyia governorate, Egypt. We also aimed at exploring the value of the use of the Real time PCR assay for detection of W. bancrofti microfilarial DNA in the mosquito vector as a monitoring tool complementary to immunochromotagraphic card test (ICT) in transmission assessment surveys (TAS) for verification of interruption of transmission of LF disease in a locality at the national level. TAS have been conducted in the two villages among the primary school children aged 6-7 years old using ICT together with MX for Culex pipiens female gravid mosquitoes in order to define the current transmission status of the disease and declare whether LF has been successfully eliminated from this area. The results of ICT were 100% negative with no positive cases for antigenemia detected in neither of the two villages as well as the LDR assay was 100% negative for the W. bancrofti microfilaria DNA. Our findings postulate that LF seems no longer to be a problem in this area and MDA can be stopped with declaration of LF elimination and reaching the endpoints in these areas. It has been fruitful and conclusive to apply MX technique in conjunction with ICT based TAS in surveillance strategy for accurate assessment of ongoing LF transmission in LF previously endemic communities.Recommendations included planning of post-MDA surveillance five years later from order to monitor the resurgence of LF in these areas if occurred, as well as implementation of MX technique when investigating LF transmission at the instance.