East African x Galla goats, when infected with Trypanosoma congolense isolates from the Kilifi area of Kenya by Glossina morsitans centralis, did not develop the characteristic
chancre reaction at the
bite sites, whereas
bites of tsetse infected with the cloned T. congolense IL.1180 from Serengeti, Tanzania, resulted in chancres in the same goats. Histological changes could not be observed in skin biopsies collected 8 or 9 days after
infection with Kilifi isolates. However, all goats became parasitemic about 10 days after challenge. It is concluded that the absence of
chancre development is a characteristic feature of T. congolense parasites from Kilifi. The
isoenzyme analysis of clones of two T. congolense Kilifi isolates and the T. congolense clone IL.1180 indicated that they belong to different zymodemes.
Neutralizing antibodies to homologous metacyclic variable
antigen types were detected in six out of seven (86%) of the sera from goats infected with a clone or stock of a T. congolense Kilifi isolate, 20 days after
infection. Goats primed by tsetse transmitted
infection with a stock or clone of T. congolense from Kilifi and treated with
Berenil were, in three out of eight cases (37%), not immune to homologous challenge. It is suggested that the reduced immune response to metacyclic variable
antigen types could be a result of the absence of cellular infiltration, i.e.,
chancre development in the skin at the tsetse
bite site. It is concluded that the use of the
chancre reaction as a marker for serodeme analysis of recently isolated stocks of T. congolense from Kilifi was not feasible.