Abstract
BackgroundAnopheles darlingi is the main malaria mosquito vector in the Amazonia region. In spite of being considered a riverine, forest-dwelling species, this mosquito is becoming more abundant in peri-urban areas, increasing malaria risk. This has been associated with human-driven environmental changes such as deforestation.MethodsMicrosatellites were used to characterize A. darlingi from seven localities along the Madeira River, Rondônia (Brazil), collected in the early and late periods of the rainy season.ResultsTwo genetically distinct subpopulations were detected: one (subpopulation A) was associated with the late rainfall period and seems to be ecologically closer to the typical forest A. darlingi; the other (subpopulation B) was associated with the early rainfall period and is probably more adapted to drier conditions by exploiting permanent anthropogenic breeding sites. Results suggest also a pattern of asymmetric introgression, with more subpopulation A alleles introgressed into subpopulation B. Both subpopulations (and admixed mosquitoes) presented similar malaria infection rates, highlighting the potential for perennial malaria transmission in the region.ConclusionsThe co-occurrence of two genetically distinct subpopulations of A. darlingi adapted to different periods of rainfall may promote a more perennial transmission of malaria throughout the year. These findings, in a context of strong environmental impact due to deforestation and dam construction, have serious implications for malaria epidemiology and control in the Amazonian region.
Highlights
Anopheles darlingi is the main malaria mosquito vector in the Amazonia region
Human-biting mosquito densities reach a peak in March-April, with over 30 bites per human per hour, whereas in the dry season biting rates fall to nearly zero [19]
In urban and suburban areas of the region, an additional density peak is recorded between the end of the dry season and the beginning of the rainy season (October-November) and malaria transmission continues throughout the year [19]
Summary
In spite of being considered a riverine, forest-dwelling species, this mosquito is becoming more abundant in peri-urban areas, increasing malaria risk. This has been associated with human-driven environmental changes such as deforestation. Anopheles darlingi is a major malaria mosquito vector in the Americas It is of particular importance in the Amazon basin where most malaria cases occur in South America [1,2]. Mosquito populations of this species display great behavioural plasticity and morphological, biological and genetic diversity [1,3,4,5,6] This vector has been found at high densities in areas affected by deforestation and anthropogenic environmental changes [7]
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