Composition of sand fly fauna (Diptera: Psychodidae) and detection of Leishmania DNA (Kinetoplastida: Trypanosomatidae) in different ecotopes from a rural settlement in the central Amazon, Brazil

Background: Phlebotomine sand flies (Diptera: Psychodidae) are vectors of Leishmania species, the etiological agents of leishmaniasis, which is one of the most important emerging infectious diseases in the Americas. In the state of Amazonas in Brazil, anthropogenic activities encourage the presence of these insects around rural homes. The present study aimed to describe the composition and distribution of sand fly species diversity among the ecotopes (intradomicile, peridomicile and forest) in an area of American cutaneous leishmaniasis transmission and detect natural infection with Leishmania DNA to evaluate which vectors are inside houses and whether the presence of possible vectors represents a hazard of transmission.

Results: Phlebotomine sand flies were collected using light traps. A total of 2469 specimens representing 54 species, predominantly females (71.2%), were collected from four sites. Polymerase chain reaction analysis was performed on 670 samples to detect Leishmania DNA. Most of the samples (79.5%) were collected in the forest, with areas closer to rural dwellings yielding a greater abundance of suspected or proven vectors and a larger number of species containing Leishmania DNA. Nyssomyia umbratilis and Bichromomyia flaviscutellata were found near rural homes, and Ny. umbratilis was also found inside homes. Leishmania DNA was detected in different species of sand flies in all ecotopes, including species with no previous record of natural infection.

Conclusions: There is no evidence that vectors of American cutaneous leishmaniasis are becoming established inside homes, but there are sand flies, including Ny. umbratilis and other possible vectors, in environments characterized by a human presence. These species continue to be predominant in the forest but are prevalent in areas closer to ecotopes with a greater human presence. The existence of proven or suspected vectors in this ecotope is due to the structural organization of rural settlements and may represent a hazard of transmission. Although the detection of Leishmania DNA in species that were not previously considered vectors does not mean that they are transmitting the parasite, it does show that the parasite is circulating in ecotopes where these species are found.