Diversity and natural infection of phlebotomine sand flies (Diptera, Psychodidae) in an endemic area of American tegumentary leishmaniasis in southeastern Bahia, Brazil.

Background: The Cacao Region spans several municipalities in the state of Bahia. It is one of the major foci of American tegumentary leishmaniasis (ATL) in Brazil. We report the findings of a pilot cross-sectional study describing the phlebotomine fauna found around living sites of newly diagnosed ATL cases in that area.

Methods: The sand fly fauna was studied from May 2018 to June 2019 via an entomological survey, as recommended by the Brazilian Ministry of Health.

Results: Six hundred nineteen phlebotomine sand flies of 20 species were captured: 272 males (44%) and 347 females (56%). Nyssomyia whitmani was the most prevalent (62.2%), followed by Nyssomyia intermedia (9.2%), Evandromyia bahiensis (6.3%), endemic to Bahia, and Trichophoromyia viannamartinsi (4.5%). Ninety-four percent of the female sand flies collected were screened for infection with Leishmania (Viannia) braziliensis by polymerase chain reaction (PCR). Of the 97 sand fly pools analyzed, seven were positive for L. (V.) braziliensis: three of Nyssomyia whitmani, two of Th. viannamartinsi and one each of Psychodopygus hirsutus hirsutus and Trichopygomyia longispina. The overall value of minimum infection rate (MIR) was 2.2%, and its stratification rates for the above species were 1.9, 10, 33 and 50%, respectively. All positive pools consisted of phlebotomine sand flies collected from the peridomiciles and extradomiciles of homes in the municipality of Taperoá in July 2018, resulting in an adjusted MIR of 7.8%, with 50% of the pools positive for L. (V.) braziliensis during that outbreak of ATL.

Conclusions: Our findings suggest that areas experiencing outbreaks of ATL in affected regions present high proportions of infected phlebotomine sand flies involving a variety of species, some not usually considered involved in the L. (V.) braziliensis transmission cycle, such as Th. viannamartinsi.