COMPARISON OF THE SUSCEPTIBILITY OF DIFFERENT GLOSSINA SPECIES TO SIMPLE AND MIXED INFECTIONS WITH TRYPANOSOMA (NANNOMONAS) CONGOLENSE SAVANNA AND RIVERINE FOREST TYPES

Teneral Glossina morsitans mositans, G.m.submorsitans, G.palpalis gamb iensis and G.tachinoides were allowed to feed on rabbits infected with Trypanosoma congolense savannah type or on mice infected with T.congo lense riverine-forest type. The four tsetse species and subspecies wer e also infected simultaneously in vitro on the blood of mice infected with the two clones of T.congolense via a silicone membrane, The infec ted tsetse were maintained on rabbits and from the day 25 after the in fective feed, the surviving tsetse were dissected in order to determin e the infection rates. Results showed higher mature infection rates in morsitans-group tsetse flies than in palpalis-group tsetse flies when infected with the savannah type of T.congolense. In contrast, infecti on rates with the riverine-forest type of T.congolense were lower, and fewer flies showed full development cycle. The intrinsec vectorial ca pacity of G.m.submorsitans for the two T.congolense types was the high est, whereas the intrinsic vectorial capacity of G.p.gambiensis for th e Savannah type and G.m.,morsitans for the riverine-forest type were t he lowest. Among all tsetse which were infected simultaneously with th e two types of T.congolense, the polymerase chain reaction detected on ly five flies which had both trypanosome tars in the midgut and the pr oboscis. Ail the other infections were attributable to the savannah ty pe. The differences in the gut of different Glossina species and subsp ecies allowing these two sub-groups of T.congolense to survive better and undergo the complete developmental cycle more readily in some spec ies than other are discussed.