Phlebotomine sand fly (Diptera : Psychodidae) seasonal distribution and infection rates in a defined focus of Leishmania tropica

A two-year study was conducted of phlebotomine sand, fly fauna in a defined focus of Leishmania tropica. A total of 17,947 sand flies representing 10 species were collected from the location. Phlebotomus guggisbergi, a vector of L. tropica in Kenya, was the most prevalent species through the entire period, representing about 80% of the total catch. There was marked seasona l fluctuation in the populations of the three most common species, with hig hest population levels reached in December and lowest levels reached in Jul y and August. Leishmania-like infections were encountered in 489 P. guggisb ergi. No flagellate infections were observed in any other species of sand f ly. Although infected P. guggisbergi were collected during each month of th e year, the percent parous infected flies was highest (27.5%) during the No vember through January time period. These data show that the greatest risk of transmission to humans at this focus occurs during December, when the ve ctor is prevalent and infections are common.