DIRECT EVIDENCE FOR PREFERENTIAL MULTIPLICATION OF BABESIA-GIBSONI INYOUNG ERYTHROCYTES

To clarify the effect of the age of host erythrocyte on the multiplica tion of Babesia parasites, B. gibsoni was cultured together with retic ulocytes, immature erythrocytes, or mature erythrocytes from dogs. Par asitemia reached peak levels (34.1 % +/- 15.8 %) at cultivation day 8 in immature-erythrocyte culture, whereas the highest parasitemia attai ned in mature-cell culture was only 3.6 % +/- 2.2 % at day 5. These re sults clearly demonstrate that B. gibsoni parasites preferentially inv ade and multiply in young erythrocytes rather than in mature cells.