The sequential cellular changes in the local skin reaction produced in goats by Glossina morsitans morsitans infected with Trypanosoma (Trypanozoon) brucei.

Sequential biopsies of the skin reaction elicited in goats by Glossina morsitans morsitans infected with Trypanosoma (Trypanozoon) brucei were examined histologically to identify and to quantify the cellular populations involved in the reaction. The peak of the tissue response occurred 7-8 days after challenge with infected tsetse and preceded the initial detection of parasitaemia by 4-5 days. Microscopically, the cellular reaction was characterized initially by a marked infiltration of polymorphonuclear leucocytes (PMN) which were replaced by lymphoid cells. Plasma cells and macrophages were numerous during the decline of the skin reaction. Marked enlargement of, and germinal centre formation in the regional lymph node accompanied the development and regression of the chancre. The results suggest that the formation of a chancre is dependent on the skin thickness of the host at the site of tsetse challenge.