Abstract
BackgroundLymphatic filariasis (LF) is a neglected tropical disease transmitted by mosquitoes. Nepal has implemented a national effort to eliminate LF by 2020 through mass drug administration (MDA) using diethylcarbamazine (DEC) and albendazole (ALB). We assessed the impact of MDAs on LF in selected districts of Nepal after the recommended six MDA rounds had been completed.Methodology and principal findingsBaseline surveys were conducted in seven districts and mapping data were used as baseline in the other three districts before starting MDA in 2009. LF antigen (Ag) prevalence ranged from 1.06% to 20% among districts included in the baseline and mapping study. The number of people who received DEC and ALB were recorded during each MDA round and population-based cluster surveys were conducted at least once in each district during the life of the program. The reported MDA coverage in five districts was consistently at least 65%. Two districts achieved the targeted coverage in four out of five rounds and the rest three districts achieved the target only in the first round. A pre-transmission assessment survey (pre-TAS) was conducted in one sentinel site and at least one spot check site in each of the districts after five MDA rounds. In pre-TAS, all the sites of five districts (Pyuthan, Arghakhanchi, Kaski, Bhaktapur, and Kathmandu) and all but one spot check site of Lalitpur district had LF Ag < 2% (ranging from 0.0% to 1.99%). Transmission assessment survey (TAS) was conducted in six evaluation units (EUs) consisting of six districts qualified on pre-TAS. Though MDA coverage of 65% was not achieved in three districts (Kathmandu, Lalitpur and Bhaktapur), Nepal government in consultation with World Health Organization (WHO) decided to conduct TAS. All six EUs achieved the LF Ag threshold required to stop MDA in TAS, despite the low reported MDA coverage in those three districts.ConclusionsAlthough Nepal has achieved significant progress towards LF elimination, five rounds of MDA were not sufficient to disrupt the transmission cycle in all districts, probably because of high baseline prevalence.
Highlights
Lymphatic filariasis (LF) is a vector-borne neglected tropical disease of human caused by Brugia malayi, Brugia timori and Wuchereria bancrofti, and transmitted by Culex, Anopheles and Aedes spp. mosquitoes [1]
There was a marked decrease between baseline and pre-transmission assessment survey (pre-Transmission assessment survey (TAS)) surveys
In all but one of the sites from Lalitpur, LF Ag ranged from 0.0% to 0.98%, which is below the 2.0% LF Ag threshold; one spot check site in a peri-urban area of Lalitpur reported a LF Ag of 3.0% (Table 2)
Summary
Lymphatic filariasis (LF) is a vector-borne neglected tropical disease of human caused by Brugia malayi, Brugia timori and Wuchereria bancrofti, and transmitted by Culex, Anopheles and Aedes spp. mosquitoes [1]. Infection with filarial worms can cause significant morbidity (primarily lymphedema of legs, arms and breast, and hydrocele) and disability, impeding socioeconomic development in many endemic countries [2,3]. To achieve GPELF targets, endemic countries conduct annual mass drug administration (MDA) of the population at risk of LF using diethylcarbamazine (DEC) and albendazole (ALB) to interrupt the transmission of filarial worms, along with the management of the disease’s chronic manifestations [5,6]. Lymphatic filariasis (LF) is a neglected tropical disease transmitted by mosquitoes. Nepal has implemented a national effort to eliminate LF by 2020 through mass drug administration (MDA) using diethylcarbamazine (DEC) and albendazole (ALB). We assessed the impact of MDAs on LF in selected districts of Nepal after the recommended six MDA rounds had been completed
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