Spatial clustering and longitudinal variation ofAnopheles darlingi(Diptera: Culicidae) larvae in a river of the Amazon: the importance of the forest fringe and of obstructions to flow in frontier malaria

Abstract

Deforestation has been linked to a rise in malaria prevalence. In this paper, we studied longitudinally 20 spots, including forested and deforested portions of a temporary river in a malarigenous frontier zone. Larval habitat parameters influencing distribution of Anopheles darlingi (Diptera: Culicidae) larvae were studied. We observed that larvae were clustered in forested-deforested transitions. For the first time in the literature, it was verified that parameters determining larval distribution varied from deforested to forested areas. The proximity to human dwellings was also a significant factor determining distribution, but larvae was most importantly associated with a previously undescribed parameter, the presence of small obstructions to river flow, such as tree trunks within the river channel, which caused pooling of water during the dry season ('microdams'). In deforested areas, the most important factor determining distribution of larvae was shade (reduced luminance). Larvae were absent in the entire studied area during the wet season and present in most sites during the dry season. During the wet-dry transition, larvae were found sooner in areas with microdams, than in other areas, suggesting that flow obstruction prolongs the breeding season of An. darlingi. Adult mosquito densities and malaria incidence were higher during the dry season. Our data correlate well with the published literature, including the distribution of malaria cases near the forest fringes, and has permitted the creation of a model of An. darlingi breeding, where preference for sites with reduced luminance, human presence and microdams would interact to determine larval distribution.

Deforestation and Malaria on the Amazon Frontier: Larval Clustering of Anopheles darlingi (Diptera: Culicidae) Determines Focal Distribution of Malaria

“…1,11,12 We have demonstrated increased A. darlingi larval densities at foresteddeforested transitions of a small river and proposed that deforestation may affect A. darlingi binomics by creating a new and unique ecosystem: the "forest fringe ecosystem." 13 In this article, initially we performed a "macrospatial analysis" to compare larval samplings at water collections located in forested, deforested, and forest fringe areas ("transitional water collections") in a typical side road of a frontier colonization project. We showed transitional water collections are found to harbor greater number of A. darlingi larvae than forested or deforested habitats.…”

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

“…[40][41][42] Statistical analysis of environmental variables using a principal component analysis or canonical correspondence analysis can reveal distinct habitat diversification among species that share a geographic distribution. 43 Habitat generalist species may be less affected by ecological variation *Address correspondence to Sascha N. McKeon, University at Albany School of Public Health, 1400 Washington Avenue, Albany, NY 12222.…”

Perturbações no ambiente natural, e emergência de habitats larvais ocupados por espécies de Anopheles Meigen (Diptera: Culicidae) em assentamento rural no sudoeste da Amazônia brasileira

“…Compreender as principais características dos habitats larvais e os respectivos fatores socioambientais associados aperfeiçoa as estratégias de controle da malária. Apesar da importância epidemiológica e preventiva de estudos de larvas, o conhecimento e produção científica sobre o assunto são ainda relativamente escassos (Manguim, 1996;Barros et al, 2011). O objetivo da pesquisa vetorial é compreender e definir os parâmetros que moldam o perfil da malária em uma determinada área, prevendo zonas de risco e alvejando os esforços de controle e, principalmente, prevenção da transmissão da doença.…”

“…Considerando-se o principal vetor no continente sul-americano, há registros de relativa abundância de larvas de Anopheles (Nyssorhynchus) darlingi presentes em corpos de água de natureza artificial (Vittor et al, 2009). Salienta-se que alterações ecológicas consequentes à presença humana promovem mudanças no comportamento de oviposição dos mosquitos vetores, além de proliferar criadouros para a espécie (Barros et al, 2011). Apesar de o An.…”

“…Foram estipuladas dois tipos de variáveis utilizando-se características ambientais e físico-químicas relacionadas à bioecologia das larvas de anofelíneos, a saber: as ambientais, de natureza qualitativa, associadas à fisionomia da paisagem; e as físico-químicas, quantitativas, voltadas às condições da água (McKeon et al, 2013;Barros et al, 2011;Vittor et al, 2009;Nagm et al, 2007).…”