Description of malaria vectors (Diptera: Culicidae) in two agricultural settlements in the Western Brazilian Amazon

Abstract

The majority of malaria cases in South America occur in rural areas of the Amazon region. Although these areas have a significant impact on malaria cases, few entomological studies have been carried out there. This study aimed to describe entomological parameters in settlements in Rondonia State, Brazil. Collections of anopheles were carried out using the Protected Human Attraction Technique (PHAT). The risk and the potential for malaria transmission were assessed using the human biting rate (HBR), the sporozoite rate (SR) and the entomological inoculation rate (EIR). The results confirmed that Nyssorhynchus darlingi is the predominant species in the two studied locations. Although settlement in the two study sites has occurred at different times, the species richness found was low, showing that environmental changes caused by anthropological actions have probably favor the adaptation of Ny. darlingi species. From the total of 615 anopheline mosquitoes assessed, seven (1.1%) were positive for Plasmodium sp. infections. The EIR revealed that Ny. darlingi contributes to malaria transmission in both locations, as it was responsible for 0.05 infectious bites in humans at night in the old settlement and 0.02 in the recent occupation. In the two study sites, the biting occurred more frequently at dusk. Nyssorhynchus darlingi was prevalent in areas of recent colonization but, even when present in a low density, this species could maintain the transmission of malaria in the older settlement. The entomological information obtained in this study is important and may aid the selection of vector control actions in these locations.

Mosquitos anofelinos envolvidos na transmissão da malária humana no município de Cruzeiro do Sul, estado do Acre, Amazônia brasileira

“…as características descritas do An. darlingi, como abundância, frequência, comportamento hematofágico noturno com atividade durante todo o horário de coleta 26,27 , portador de infecção tanto por P. vivax quanto P. falciparum, verifica-se que o seu papel vetorial é muito importante para a manutenção da transmissão da malária em Cruzeiro do Sul. As estratégias de controle vetorial utilizadas nesse município, principalmente a borrifação intradomiciliar com inseticidas do grupo dos piretroides e o uso de mosquiteiros impregnados com inseticida de longa duração, são adequadas; porém, são necessários estudos que avaliem a possibilidade de resistência dos mosquitos aos inseticidas e a ação desses na população e no ambiente, visando seu uso racional.…”

Change in the faunal composition of mosquitoes (Diptera: Culicidae) along a heterogeneous landscape gradient in the Brazilian Amazon

“…On a more local scale, people living in rural Amazonian settlements are constantly affected by mosquito-borne diseases, which might be an effect of landscape modification due to sustenance practices, such as deforestation for subsistence agriculture or extensive livestock farming, fish farming ponds, hunting, and others [ 22 , 23 ]. As the type of landscape can influence the mosquito community, our study primarily aimed to compare the abundance, richness, and patterns of the composition of mosquitoes among the forest, forest edge, and peridomicile habitat in small farms of Brazilian Central Amazon, and also identify the species composition of each habitat.…”