RELATIONSHIPS BETWEEN PROTEASE ACTIVITY, HOST BLOOD AND INFECTION-RATES IN GLOSSINA-MORSITANS SPP INFECTED WITH TRYPANOSOMA-CONGOLENSE, TRYPANOSOMA-BRUCEI AND T-SIMIAE

Midgut protease activity in Glossina morsitans centralis and G. m. mor sitans, at 48 h post bloodmeal averaged 1.8 IU of trypsin-like activit y. These two tsetse subspecies differ in their susceptibility to trypa nosome infection. Except for low levels in flies fed on waterbuck bloo d (0.7IU), activity did not differ in flies fed a variety of host bloo ds (goat, pig, cow, buffalo, eland) and trypanosome species (Trypanoso ma congolense, T. brucei, T. simiae). Protease activity was also not c orrelated with infection rates, despite large differences in infection rates among experiments. Nevertheless, addition of 0.06M D(+)-glucosa mine to parasitaemic blood resulted in a three-fold reduction in prote ase activity, coincident with a large increase in infection rate. This effect did not occur when parasites or D(+)-glucosamine were added al one to the bloodmeal, suggesting that the effect was due to metabolism of D(+)-glucosamine by parasites.