Small-scale land-use variability affects Anopheles spp. distribution and concomitant Plasmodium infection in humans and mosquito vectors in southeastern Madagascar

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.

Using mobile phones as acoustic sensors for high-throughput mosquito surveillance

“…Here, our first step was to establish the baseline species composition, by collecting live mosquitoes in traps or bags and identifying them using microscopy. We found both Anopheles and Culex mosquitoes ( Zohdy et al, 2016 ), which we identified only to genus level in the field. We recorded several minutes of acoustic data from both, to form a frequency distribution reference database specific to the RNM field site, for comparing new data from phone recordings ( Figure 4A,B ).…”

Variation in Anopheles distribution and predictors of malaria infection risk across regions of Madagascar

“…Marrama et al (1995) showed rice elds had the highest percentage of mosquito larvae and provide half of all positive larval breeding habitats (59). Zohdy et al (2016) demonstrated that Anopheles species are the dominant mosquitoes in agricultural and village settings, and are the minority in forest settings (28).…”

“…In eastern humid tropical forest, Anopheles mosquitoes are more abundant in agricultural land and village environments than surrounding forests, indicating forest clearance as a possible driver of local malaria transmission (28). A cross-sectional study of communities in southeast Madagascar demonstrated that bed net use protected against malaria, while rural individuals in lower socioeconomic brackets, between 6-14 years of age, were at higher risk of infection (23,29).…”

Experimental logging alters the abundance and community composition of ovipositing mosquitoes in the southern Appalachians

“…The influence of logging per se on adult mosquito communities has not yet been directly examined, but several prior studies have examined how urbanisation or land‐use gradients, which integrate a suite of landscape changes including loss of intact forest, influence adult mosquito communities. Studies of land‐use gradients in the Peruvian Amazon (Johnson et al ., ), Thailand (Thongsripong et al ., ), Spain (Ferraguti et al ., ), Madagascar (Zhody et al ., ), and remote Australian islands (Meyer Steiger et al ., ) generally find the highest mosquito abundance and diversity in rural, forested sites with high vegetative cover relative to more urban habitats. However, in Anopheles species, the combined effects of deforestation and conversion to agriculture are highly species‐specific, with some taxa increasing in abundance with land‐use change, and others decreasing (Yasuoka & Levins, ).…”

“…Although the impacts of deforestation on vector ecology and resulting disease risk have been of long-standing interest (reviewed in Walsh et al, 1993), only recently have studies explicitly considered how anthropogenic changes to intact forests alter the diversity and abundance of the invertebrate taxa that commonly serve as disease vectors (e.g. Thongsripong et al, 2013;Meyer Steiger et al, 2016;Zhody et al, 2016).…”