Abstract
BackgroundStudies on vector behaviour should be conducted in order to evaluate the effectiveness of vector control measures on malaria protection in endemic areas of Latin America, where P. vivax predominates. This work aims to investigate the fauna of anopheline mosquitoes and verify the impact of integrated vector management in two colonization projects in the Careiro Municipality, Western Brazilian Amazon.MethodsFour mosquitoes’ captures were carried out from August 2008 to March 2010, with an interval of six months between each collection. Since September 2009 a large programme to reduce the burden of malaria has started in the two communities by distribution of insecticide-treated bed nets (ITN) and intensification of indoor residual spraying (IRS). Human biting rates (HBRs), entomological inoculation rates (EIRs), malaria incidence rate (MIR) and Plasmodium carrier’s prevalence were used as outcomes to estimate the impact of the control measures.ResultsA total of 3,189 anophelines were collected, belonging to 13 species. Anopheles darlingi was the predominant species in the period (42.6%), followed by Anopheles albitarsis (38.4%). An. darlingi HBRs showed a notable decreasing trend from the start to the end of the study. Conversely, An. albitarsis increased its contribution to overall HBRs throughout the study. For An. darlingi there was a significant positive correlation between HBRs and MIR (p = 0.002). Anopheles albitarsis HBRs showed a significant negative correlation with the corresponding MIR (p = 0.045). EIR from total anophelines and from An. darlingi and An. albitarsis presented decreasing patterns in the successive collections. Four species of anophelines (An. darlingi, An. albitarsis, Anopheles braziliensis and Anopheles nuneztovari) were naturally infected with Plasmodium, albeit at very low infection rates. There were a decrease in the MIR for both vivax and falciparum malaria and in the prevalence of Plasmodium vivax and Plasmodium falciparum carriers during the period of study.ConclusionsThere is strong evidence of association between the density of An. darlingi and the incidence of malaria in the studies sites, further highlighting the importance of this vector in malaria transmission in this region. An. darlingi susceptibility to control using ITN and IRS is likely to be high in the rural settlements studied.
Highlights
Studies on vector behaviour should be conducted in order to evaluate the effectiveness of vector control measures on malaria protection in endemic areas of Latin America, where P. vivax predominates
An. darlingi predominates in Brazilian endemic areas, other species of anophelines have been implicated as malaria vectors in distinct Amazonian settings, namely Anopheles albitarsis s.l., Anopheles nuneztovari, Anopheles triannulatus and Anopheles intermedius [8,13,14,15]
Data presented here represent an important contribution to the knowledge of the epidemiology of malaria transmission and vector control in agricultural settlements in the Amazon, indicating that An. darlingi is the vector responsible by the transmission in these sites, and that integrated measures using impregnated bed nets and residual spraying may reduce substantially the man-vector contact and malaria incidence
Summary
Studies on vector behaviour should be conducted in order to evaluate the effectiveness of vector control measures on malaria protection in endemic areas of Latin America, where P. vivax predominates. Infection, with highly anthropophilic and endophagic behaviour [7,8,9] This species is described in tropical and subtropical regions in Central and South Americas especially in areas of low altitude, preferring large bodies of water in forested areas [10]. The larvae are adapted to the water margins, preferably deep, clean, slightly cloudy, sunny or partially shaded ones, hiding among the vegetation or debris During rainy seasons they change their behaviour with a preference for breeding at smaller size and depth water bodies [11,12]. An. darlingi predominates in Brazilian endemic areas, other species of anophelines have been implicated as malaria vectors in distinct Amazonian settings, namely Anopheles albitarsis s.l., Anopheles nuneztovari, Anopheles triannulatus and Anopheles intermedius [8,13,14,15]. In most of its territory, including the dry north-east and the central areas, this anopheline is exophilic and zoophilic, preferring to attack the cattle [16]
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