This study was undertaken to determine the epidemiological importance of fanniid flies on warble fly infestations. The local species of Fanniidae as well as those utilized by Dermatobia hominis to carry its eggs were identified, and the population dynamics of the most abundant species were studied. In order to accomplish this task, five traps with rotten bovine liver as bait were used. These traps were settled into a ciliate forest bordered by pastures and grazed continuously by cattle. The experiment was carried out at Embrapa Gado de Corte, in Campo Grande, Mato Grosso do Sul, Brazil, situated at 20º27'S and 54º37'W. The capture of the insects was done weekly, from August 9, 1999 to August 3, 2000. A total of 40,629 fanniid flies which belonged to five different species of the genera Fannia were captured: F. pusio, F. heydenii, F. bahiensis and F. longipila, and one species which needs further identification. The most frequent species was F. pusio, with 63.20% of the total captured flies, followed by F. heydenii with 28.82%. Eggs of D. hominis were observed only on 0.44% (45 specimens) of the F. heydenii females captured, mainly on the ones captured in August and September. The average number for D. hominis eggs, per specimen, was 15.98±7.13. The only vector body region, where the eggs of D. hominis were found, was the abdomen. F. heydenii predominated during the dry season (May to September) and at the beginning of the rainy season (October and November). The number of specimens bearing eggs of D. hominis was greater at the end of the annual dry season, what explains the high incidence of this parasite in cattle during September and October.
Vectors; warble fly; epidemiology; Brazilian savannas
