Evaluation of ivermectin mass drug administration for malaria transmission control across different West African environments

Abstract

BackgroundMass drug administration (MDA) of ivermectin to humans for control and elimination of filarial parasites can kill biting malaria vectors and lead to Plasmodium transmission reduction. This study examines the degree and duration of mosquitocidal effects resulting from single MDAs conducted in three different West African countries, and the subsequent reductions in parity and Plasmodium sporozoite rates.MethodsIndoor-resting, blood-fed and outdoor host-seeking Anopheles spp. were captured on days surrounding MDAs from 2008–2013 in Senegalese, Liberian and Burkinabé villages. Mortality was assessed on a portion of the indoor collection, and parity status was determined on host-seeking mosquitoes. The effect of MDA was then analysed against the time relative to the MDA, the distributed drugs and environmental variables.ResultsAnopheles gambiae survivorship was reduced by 33.9% for one week following MDA and parity rates were significantly reduced for more than two weeks after the MDAs. Sporozoite rates were significantly reduced by >77% for two weeks following the MDAs in treatment villages despite occurring in the middle of intense transmission seasons. These observed effects were consistent across three different West African transmission dynamics.ConclusionsThese data provide a comprehensive and crucial evidence base for the significant reduction in malaria transmission following single ivermectin MDAs across diverse field sites. Despite the limited duration of transmission reduction, these results support the hypothesis that repeated MDAs with optimal timing could help sustainably control malaria as well as filarial transmission.Electronic supplementary materialThe online version of this article (doi:10.1186/1475-2875-13-417) contains supplementary material, which is available to authorized users.

Ivermectin-treated cattle reduces blood digestion, egg production and survival of a free-living population of Anopheles arabiensis under semi-field condition in south-eastern Tanzania

“…arabiensis than control cattle for up to 1 week post-treatment. Like orally-treated cattle, many previous studies found that orally-treated humans reduced the survival of Anopheles mosquitoes for at least 1 week [35, 40, 42, 44, 85]. …”

“…The effects of ivermectin on digestion of blood meal in the stomach of surviving mosquitoes suggests that it may also inhibit establishment of parasite development in mosquitoes [37]. In contrast, the MDA to humans contributed to decreased malaria transmission by reducing survival of wild Anopheles mosquitoes for 1 week that consequently shifted age structure to young females (less infectious mosquitoes), and reduced sporozoite rates for at least 2 weeks [39, 44, 45]. Therefore, the long lasting effects of ivermectin-treated cattle could similarly reduce the vectorial capacity of An.…”

Characterization of the target of ivermectin, the glutamate-gated chloride channel, fromAnopheles gambiae

“…Mass drug administration of IVM is effective at killing A. gambiae mosquitoes Alout et al, 2014), inhibiting P. falciparum sporogony in A. gambiae and disrupting malaria parasite transmission in endemic villages (Kobylinski et al, 2011;Alout et al, 2014). Thus, IVM mass drug administration has strong potential to be developed as a novel tool for malaria parasite transmission control.…”

“…IVM, when imbibed by vectors from host-treated blood meals, has proven to efficiently kill or disable A. gambiae s.s. both in the lab and in the field Sylla et al, 2010). More recently, IVM mass drug administration in multiple locations across West Africa has been shown to temporarily reduce the proportion of Plasmodium falciparum-infected A. gambiae in IVM-treated villages (Kobylinski et al, 2011;Alout et al, 2014). Sub-lethal doses of IVM have also been shown to inhibit the sporogony of P. falciparum in A. gambiae s.s. and impair coordinated flight patterns (Butters et al, 2012;Kobylinski et al, 2012).…”

Efficacy and Safety of High-Dose Ivermectin for Reducing Malaria Transmission (IVERMAL): Protocol for a Double-Blind, Randomized, Placebo-Controlled, Dose-Finding Trial in Western Kenya

“…Similarly, in 3 different West African transmission settings, this same dose reduced An. gambiae survivorship by 33.9% for 1 week, their parity rates for more than two weeks, and sporozoite rates by more than 77% for 2 weeks [18]. …”