Transmission of the human filarial parasite Mansonella ozzardi by Culicoides phlebotomus (Williston) (Diptera: Ceratopogonidae) in coastal north Trinidad

ABSTRACT

Between June 1976 and November 1977, man-baited and truck-trap collections of Haematophagous Diptera were made on the foreshore of Las Cuevas Bay, north Trinidad, close to a fishing village where Mansonella ozzardi infections are prevalent in man. Culicoides phlebotomus (Will.) predominated in all collections, forming 96.1 percent of the total catch. Analysis of blood-meals from engorged C. phlebotomus collected by truck trapping at sunset indicated frequent feeding on mammals, with feeds on man comprising 47 percent of those identified. Filarial larvae were found in 0.8 percent of 6767 females of C. phlebotomus captured on man, and five (0.08 percent) had infective larvae of M. ozzardi. Similarly, 1.3 percent of 7028 females obtained by truck trapping were infected, including nine (0.13 percent) with infective larvae. Growth rates of M. ozzardi in C. phlebotomus were determined by experimental infection and were used to estimate daily survival rates of wild-caught females of C. phlebotomus based on filarial growth stages found in them. The daily survival rate varied from 85 to 95 percent in flies 1-3 days after infection to 69 percent in flies six days after infection. It was estimated that a person spending one hour on the beach every morning would receive 38 infective bites from C. phlebotomus per annum. (AU)