Survey of phlebotomine sand flies (Diptera: Psychodidae: Phlebotominae) in Três Lagoas Municipality, Mato Grosso do Sul State, Brazil, an area of intense transmission of American visceral leishmaniasis

Abstract

ABSTRACT

The objectives of this study were to survey urban and rural sandfly species; to investigate the spatiotemporal distribution of sandflies in the studied area; to determine the levels of natural infection of female sandflies with Leishmania; to determine the impact of the application of insecticides on the vector population; to correlate entomological, epidemiological, and biogeographic data to identify conditions that are favorable to the occurrence of leishmaniasis; and to provide information for the control of leishmaniasis in the studied area. Specimen collection was carried out once a month between August 2000 and December 2006, using CDC traps. In total, 4,277 specimens were captured (3,071 males and 1,206 females), comprising 14 sandfly species. Of these specimens, 76.61% were found in peridomestic areas. Lutzomyia longipalpis, the most frequent species (87.02%), had a standardized constancy index of 1.0. The spatiotemporal distribution pattern of this species confirmed its important role in the transmission of American visceral leishmaniasis. Infection by flagellates suggestive of Leishmania spp. was found in 1.18% of dissected Lu. longipalpis females. Statistical analyses showed a significant correlation (p < 0.05) between the number of sandflies and the precipitation and humidity levels. Linear regression tests showed a significant association between the number of Lu. longipalpis captured and the cases of human and canine American visceral leishmaniasis in a given area (p < 0.001). The vector population was reduced in 2002 by the application of insecticides; however, it increased in subsequent years due to the irregularity of spraying. Strategies that can be used for disease control in this area are suggested in the conclusion.