Trypanosoma congolense infection in sheep: ultrastructural changes in the skin prior to development of local skin reactions.

Events occurring in the skin of sheep prior to development of Trypanosoma congolense-induced local skin reactions (chancres) were studied using electron microscopy. Three days after infection, few trypanosomes were present in the dermal collagen. However, these parasites were more abundant 5 days after infection, and were also found in dermal lymphatics and in the connective tissue matrix between collagen bundles. Mast cells in the skin obtained 5 days after infection showed evidence of degranulation. These events may play a role during the induction phase of trypanosomal chancres.