Habitat suitability and ecological niche profile of major malaria vectors in Cameroon

Abstract

BackgroundSuitability of environmental conditions determines a species distribution in space and time. Understanding and modelling the ecological niche of mosquito disease vectors can, therefore, be a powerful predictor of the risk of exposure to the pathogens they transmit. In Africa, five anophelines are responsible for over 95% of total malaria transmission. However, detailed knowledge of the geographic distribution and ecological requirements of these species is to date still inadequate.MethodsIndoor-resting mosquitoes were sampled from 386 villages covering the full range of ecological settings available in Cameroon, Central Africa. Using a predictive species distribution modeling approach based only on presence records, habitat suitability maps were constructed for the five major malaria vectors Anopheles gambiae, Anopheles funestus, Anopheles arabiensis, Anopheles nili and Anopheles moucheti. The influence of 17 climatic, topographic, and land use variables on mosquito geographic distribution was assessed by multivariate regression and ordination techniques.ResultsTwenty-four anopheline species were collected, of which 17 are known to transmit malaria in Africa. Ecological Niche Factor Analysis, Habitat Suitability modeling and Canonical Correspondence Analysis revealed marked differences among the five major malaria vector species, both in terms of ecological requirements and niche breadth. Eco-geographical variables (EGVs) related to human activity had the highest impact on habitat suitability for the five major malaria vectors, with areas of low population density being of marginal or unsuitable habitat quality. Sunlight exposure, rainfall, evapo-transpiration, relative humidity, and wind speed were among the most discriminative EGVs separating "forest" from "savanna" species.ConclusionsThe distribution of major malaria vectors in Cameroon is strongly affected by the impact of humans on the environment, with variables related to proximity to human settings being among the best predictors of habitat suitability. The ecologically more tolerant species An. gambiae and An. funestus were recorded in a wide range of eco-climatic settings. The other three major vectors, An. arabiensis, An. moucheti, and An. nili, were more specialized. Ecological niche and species distribution modelling should help improve malaria vector control interventions by targeting places and times where the impact on vector populations and disease transmission can be optimized.

Ecological Suitability and Spatial Distribution of Five Anopheles Species in Amazonian Brazil

“…These associations are more difficult to interpret with respect to the various localities/states, because they do not represent any unambiguous environmental gradient. 57 …”

“…56 In addition, a canonical correspondence analysis (JMP, Version 7) was carried out as a secondary measure of the pattern of variation in community composition accounted for by the environmental variables. 57 All sites, regardless of species presence or absence, were included in the analysis. A species was considered a habitat generalist based on the following criteria: 1) large proportion of positive larval pools across both Brazilian states, and 2) no correlations with the environmental covariates.…”

Spatially explicit predictions of blood parasites in a widely distributed African rainforest bird

“…On the other hand, our predictions closely concur with the human malaria study in Cameroon [28], where we performed more extensive sampling. In addition, it is clear that different mosquito species have very different distributions, as is evident among species of Anopheles mosquitoes in Cameroon [53]. With avian malaria, mosquitoes of eight genera transmit the parasites [4], and there is recent evidence that mosquitoes of the genus Coquillettidia can act as vectors in Africa [49].…”

Advances and Perspectives in the Study of the Malaria Mosquito Anopheles funestus

“…On the other hand, An. funestus is scarce or completely absent along the coast [18]. Anopheles funestus disappeared from several parts of Africa after adverse climatic conditions (i.e recurrent droughts) and/or vector control programs [28].…”

“…1A). Being predominantly a savannah mosquito [18], this malaria vector is present in many other areas, such as high altitude zones (900 m in Madagascar [19], 1400 m in Central Africa [20] and up to 2000 m in Kenya [21]) and forested areas of West and Central Africa [18,[22][23][24][25]. Moreover, it can inhabit extreme dry conditions in the Sahel, when suitable breeding place are available, such as human-made irrigation zones [26,27].…”