AN EXPERIMENTAL-STUDY OF THE PERIDOMESTIC DISTRIBUTION OF LUTZOMYIA-LONGIPALPIS (DIPTERA, PSYCHODIDAE)

Lutzomyia longipalpis (Lutz & Neiva), the vector of American visceral leishmaniasis (AVL), is much more abundant in animal sheds than in hou ses on Marajo Island, Para State, Brazil. This difference in abundance is known not to reflect host preference. We show here that it also ca nnot be explained in terms of variable trapping efficiency, or insecti cide application, and we exclude animal sheds as important daytime res ting sites. In experimental sheds, the number of L. longipalpis increa sed markedly with the openness of the walls, though artificially large aggregations of flies could be generated in closed houses by using ca ged flies and hosts as attractants. We conclude that L. longipalpis te nd to congregate at sites outdoors, including animal sheds, because th ese are the places where leks can most easily form on abundant, statio nary (sleeping) and accessible hosts. These results help to explain wh y the seroprevalence of Leishmania chagasi infection is generally much higher among dogs than humans. They also indicate that human exposure to sandfly bites varies with the quality of house construction.