Hosts of Glossina Fuscipes Fuscipes and G. Pallidipes in Areas of Western Kenya with Endemic Sleeping Sickness, As Determined Using an Egg-yolk (IgY) ELISA

Bloodmeal sources of Glossina fuscipes fuscipes and G. pallidipes, from the western Kenyan foci of human African trypanosomiasis (HAT) on Mageta Island and in Busia district, were identified using an ELISA based on chicken egg-yolk (IgY) antibodies. After absorption with cross-reacting antigens, the antibodies, which were produced against representatives of eight families of vertebrate host, were capable of differentiating serum from the different families. With the ELISA, it was possible to identify the family of host for 100% of laboratory-fed flies tested up to 48 h post-bloodmeal but only for 12% of such flies tested 96 h post-feed. Subsequently, attempts were made to identify the family of host that was the source of the (most recent) bloodmeal for each of 223 wild-caught flies, and these attempts were successful for 142 (63.7%) of the samples. Among the flies with identified bloodmeals, most (81.9%) of the G. f. fuscipes caught on Mageta Island had last fed on reptiles whereas most of the G. f. fuscipes (70.4%) and G. pallidipes (57.1%) caught in Busia had last fed on bovids. Bloodmeals of human origin accounted for <2% of the bloodmeals identified, perhaps indicating that, in the presence of alternative hosts, humans are not attractive hosts for tsetse in the study areas. This finding may account for the low reported incidence of HAT, despite the presence of circulating human-infective trypanosomes. In Busia at least, the use of animals, especially cattle, covered in insecticide would probably be an effective method of controlling the tsetse vectors of the trypanosomes that cause human and 'animal' trypanosomiases.