Abstract
BackgroundDeforestation and land-use change have the potential to alter human exposure to malaria. A large percentage of Madagascar’s original forest cover has been lost to slash-and-burn agriculture, and malaria is one of the top causes of mortality on the island. In this study, the influence of land-use on the distribution of Plasmodium vectors and concomitant Plasmodium infection in humans and mosquito vectors was examined in the southeastern rainforests of Madagascar.MethodsFrom June to August 2013, health assessments were conducted on individuals living in sixty randomly selected households in six villages bordering Ranomafana National Park. Humans were screened for malaria using species-specific rapid diagnostic tests (RDTs), and surveyed about insecticide-treated bed net (ITN) usage. Concurrently, mosquitoes were captured in villages and associated forest and agricultural sites. All captured female Anopheline mosquitoes were screened for Plasmodium spp. using a circumsporozoite enzyme-linked immunosorbent assay (csELISA).ResultsAnopheles spp. dominated the mosquito communities of agricultural and village land-use sites, accounting for 41.4 and 31.4 % of mosquitoes captured respectively, whereas Anopheles spp. accounted for only 1.6 % of mosquitoes captured from forest sites. Interestingly, most Anopheles spp. (67.7 %) were captured in agricultural sites in close proximity to animal pens, and 90.8 % of Anopheles mosquitoes captured in agricultural sites were known vectors of malaria. Three Anopheline mosquitoes (0.7 %) were positive for malaria (Plasmodium vivax-210) and all positive mosquitoes were collected from agricultural or village land-use sites. Ten humans (3.7 %) tested were positive for P. falciparum, and 23.3 % of those surveyed reported never sleeping under ITNs.ConclusionsThis study presents the first report of malaria surveillance in humans and the environment in southeastern Madagascar. These findings suggest that even during the winter, malaria species are present in both humans and mosquitoes; with P. falciparum found in humans, and evidence of P. vivax-210 in mosquito vectors. The presence of P. vivax in resident vectors, but not humans may relate to the high incidence of humans lacking the Duffy protein. The majority of mosquito vectors were found in agricultural land-use sites, in particular near livestock pens. These findings have the potential to inform and improve targeted malaria control and prevention strategies in the region.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-016-1164-2) contains supplementary material, which is available to authorized users.
Highlights
Deforestation and land-use change have the potential to alter human exposure to malaria
The number of Anopheles mosquitoes captured in agricultural sites, village sites, and forest sites was 272, 124, and 18, respectively (Table 2)
Most of the Anopheles mosquitoes captured at agricultural sites were An. gambiae s.l. (62.1 %, n = 169), followed by An. funestus (22.4 %, n = 61)
Summary
Deforestation and land-use change have the potential to alter human exposure to malaria. The influence of land-use on the distribution of Plasmodium vectors and concomitant Plasmodium infection in humans and mosquito vectors was examined in the southeastern rainforests of Madagascar. While malaria epidemiology varies considerably in different regions of the country, with perennial transmission in the southeastern regions of Madagascar [1], specific transmission seasons in the lowland areas in the northwest, and unstable seasonal transmission in the highland (central) and semidesert areas (southwest) areas of the country, the entire population is considered to be at risk for the disease [1]. Of the five Plasmodium species capable of infecting humans with malaria, four are present in Madagascar [2], with Plasmodium falciparum as the most prevalent species, followed by P. vivax [2]. Increased financing for malaria treatment and mosquito control with insecticides has successfully decreased malaria rates in Madagascar [1], addressing environmental determinants of disease could provide additional ways of controlling malaria, including environmental management practices, such as vegetation clearance, draining swamps and modification of river boundaries [5, 6], that would increase the efficiency of programmes [5]
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