THE INFLUENCE OF HOST BLOOD ON INFECTION-RATES IN GLOSSINA-MORSITANS SSPP INFECTED WITH TRYPANOSOMA-CONGOLENSE, TRYPANOSOMA-BRUCEI AND T-SIMIAE

Trypanosoma congolense, T. brucei and T. simiae isolated from wild-cau ght Glossina pallidipes were fed to laboratory-reared G. morsitans cen tralis and G. m. morsitans to determine the effect of host blood at th e time of the infective feed on infection rates. Bloodstream forms of trypanosomes were membrane-fed to flies either neat, or mixed with blo od from cows, goats, pigs, buffalo, eland, waterbuck and oryx. The use of different bloods for the infective feed resulted in differences in infection rates that were repeatable for both tsetse subspecies and m ost parasite stocks. Goat, and to a lesser extent, pig blood facilitat ed infection, producing high infection rates at low parasitaemias. Blo od from cows and the wildlife species produced low infection rates, wi th eland blood producing the lowest. Addition Of D(+)-glucosamine (an inhibitor of tsetse midgut lectin) increased infection rates in most c ases. These results indicate the presence of species-specific factors in blood that affect trypanosome survival in tsetse. In certain hosts, factors actually appear to promote infection. The nature of these fac tors and how they might interact with midgut lectins and proteases are discussed.