Dynamics of host blood effects in Glossina morsitans sspp. infected with Trypanosoma congolense and T. brucei.

The pattern of infection in Glossina morsitans morsitans and G. m. centralis membrane-fed on eland, buffalo or goat blood mixed with Trypanosoma congolense or T. brucei was studied from day 1 to day 10. Tsetse were initially permissive vectors, with most flies harbouring infections of 10(4)-10(5) parasites on day 3. However, after a second blood meal on day 3, flies cleared many infections, with G. m. morsitans clearing more infections than G.m. centralis. Infective feeds of goat blood consistently increased final infection rates by limiting the number of infections lost between days 3 and 6. In further experiments with G. m. morsitans only, this effect was replicated by feeding flies on erythrocytes but not on serum. These results suggest that compounds from some mammalian erythrocytes match the target specificity of G. m. morsitans midgut lectins and, hence, have a protective effect on trypanosome establishment in the fly.