Induction of systemic and local basophil and eosinophil responses in guinea pigs by the feeding of the tsetse fly Glossina morsitans.

Guinea pigs infested with Glossina morsitans weekly for 5 weeks exhibited marked peripheral blood basophil and eosinophil responses to each infestation, with a dominant cutaneous basophil response to challenge infestation. G. morsitans feeding was completed within 3--10 min, depending upon prior exposure, and flies were reluctant to feed and probed longer on hyperexposed animals. Blood basophil responses exhibited the greatest increases over controls (up to 12-fold) compared to eosinophils (up to 3-fold). After the first and third infestations, both basophil and eosinophil levels increased, whereas after the second and fourth infestations both cell types declined. Greatest blood basophil responses developed after the first infestation with levels ranging from 0 to 14 +/- 9 cells/mm3 in infested animals to 0 and 2 +/- 2 cells/mm3 in uninfested controls. Eosinophilia increased with each infestation where levels ranged from 57 +/- 23 cells/mm3 after the first tsetse feeding to 110 +/- 20 cells/mm3 after the fourth infestation; compared to 11 +/- 11 to 50 +/- 12 cells/mm3 in uninfested controls. Fly-feeding sites were marked by hemorrhages, and probing behavior resulted in a line of small hemorrhages when the underside of the skin was examined. Histologically, G. morsitans feeding sites in naive guinea pigs 24 h post-infestation were dominated by mononuclear cells (93% of the infiltrate) with a weak granulocyte component, of which eosinophils were dominant (1.3%). Tsetse feeding sites in guinea pigs exposed 3 times previously were again dominated by mononuclear cells (57% of the infiltrate), but granulocytes comprised a significant part of the response (43% of the infiltrate) where basophils were dominant (25%).