Phlebotomine sandflies in British Honduras

ABSTRACT

Under experimental conditions, certain phlebotomine sandflies have been shown to be capable of transmitting Leishmania mexicana to mammalian hosts, but, although nearly 7,500 phlebotomines caught on man in British Honduras have been examined for naturally-acquired leptomonad infections, the vector of human leishmaniasis in the country remains unknown. It seems appropriate, therefore, to offer a list of the phlebotomines known to exist in British Honduras and to suggest which are the most likely to be responsible for human L.mexicana infections. Of the 22 species recorded in the country, eight species of Lutzomyia and one of Brumptomyia are known from so few specimens that they are unlikely to be involved in the transmission of leishmaniasis either to man or rodents. Lu. cayennensis, Lu. beltrani, Lu. permira and B. galindoi, for several reasons, can be eliminated from the list of possible vectors of the infection to man. The common man-biting species Lu. panamensis and Lu. shannoni, and the occasional man-biters Lu. ovallesi, Lu. ylephiletrix, and Lu. bispinosa are rarely taken in fly-traps baited with Ototylomys phyllotis; because this rodent appears to be the prime host for L.mexicana, these five species of sandfly have few opportunities of ingesting the parasite. Lu-trinidadensis is occasionally taken in rat-baited fly-traps and on man about 40 ft. above the ground but it is virtually absent from the ground level, where transmission of leishmaniasis appears to occur. Lu.deleoni is fairly common in rat-baited fly-traps set at ground level, but it accounted for about 0.4 per cent of the flies caught on man between 1963 and 1965, and for less than 0.1 per cent of man-biters collected between May 1966 and January 1967. Lu. flaviscutellata is the commonest rat-biting species at ground level and naturally-acquired leptomonad infections, which caused typical L.mexicana lesions when inoculated into hamsters, have been found in a small number of specimens of this species caught in fly-traps. L. mexicana infections have also been reported from specimens of Lu. flaviscutellata caught on map in Mexico. But of 5,323 phlebotomines taken on man between 1963 and 1965, only 23 were Lu.flaviscutellata; of 2,607 flies caught on man between May 1966 and January 1967, only six were Lu. flaviscutellata. This leaves Lu. cruciata. This is commonly taken on man and in rat-baited fly trap, there is evidence that it has a wide host-range, it has been wide distribution, it is a 'robust' fly that probably lives longer than other species, and it has transmitted leishmaniasis under experimental conditions. But of the several thousands of specimens (taken on man and in fly-traps) dissected and examined for flagellates, none have been found with the leptomonads of L. mexicana (AU)