Abstract
BackgroundThe Global Programme to Eliminate Lymphatic Filariasis (GPELF) was launched in 2000 with the goal of stopping transmission of lymphatic filariasis (LF) through yearly mass drug administration (MDA). Although preliminary surveys of the human population in Mali suggested that Wuchereria bancrofti infection was highly endemic in the Sikasso district, baseline entomological data were required to confirm high levels of transmission prior to the selection of villages in this region for a study of the impact of MDA on transmission of LF by anopheline vectors.MethodsW. bancrofti transmission was assessed in 2001 (pre-MDA) and 2002 (post-MDA) in the Central District of Sikasso in southern Mali by dissection of Anopheles mosquitoes caught using the human landing catch (HLC) method. The relative frequencies and molecular forms of An. gambiae complex were determined.ResultsThe majority (86%) of the anopheline vectors captured were identified as An. gambiae complex, and these accounted for >90% of the entomological inoculation rate (EIR) during both years of the study. There was a dramatic decrease in the number of An. gambiae complex mosquitoes captured and in the An. gambiae complex infectivity rates following MDA, accounting for the observed decrease in EIR in 2002 (from 12.55 to 3.79 infective bites per person during the transmission season). An. funestus complex mosquitoes were responsible for a low level of transmission, which was similar during both years of the study (1.2 infective bites per person during the transmission season in 2001 and 1.03 in 2002).ConclusionsBased on the entomological data from this study, the district of Sikasso was confirmed as an area of high W. bancrofti transmission. This led to the selection of this area for a multi-national study on the effects of MDA on LF transmission by anopheline vectors. Comparison of vector transmission parameters prior to and immediately following the first round of MDA demonstrated a significant decrease in overall transmission. Importantly, the dramatic variability in EIR over the transmission season suggests that the efficacy of MDA can be maximized by delivering drug at the beginning of the rainy season (just prior to the peak of transmission).
Highlights
The Global Programme to Eliminate Lymphatic Filariasis (GPELF) was launched in 2000 with the goal of stopping transmission of lymphatic filariasis (LF) through yearly mass drug administration (MDA)
This area was historically known to be endemic for W. bancrofti, and mapping surveys performed by the National Program for the Elimination of Lymphatic Filariasis confirmed a high prevalence of circulating filarial antigen (CFA) positivity in the village of Dozanso and a neighboring village in 2001
Among the 15,869 An. gambiae complex members examined by polymerase chain reaction (PCR) for specific species identification, 99.02% (15,713/15,869) were An. gambiae s.s. and 0.98% (156/15,869) was An. arabiensis
Summary
The Global Programme to Eliminate Lymphatic Filariasis (GPELF) was launched in 2000 with the goal of stopping transmission of lymphatic filariasis (LF) through yearly mass drug administration (MDA). Preliminary surveys of the human population in Mali suggested that Wuchereria bancrofti infection was highly endemic in the Sikasso district, baseline entomological data were required to confirm high levels of transmission prior to the selection of villages in this region for a study of the impact of MDA on transmission of LF by anopheline vectors. In anticipation of the launch of NLFEP activities in Mali, a pilot study of the impact of mass drug administration (MDA) with albendazole and ivermectin on W. bancrofti transmission was initiated in collaboration with the World Health Organization (WHO) in Ghana, Mali, and Nigeria.
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