DIFFERENTIAL-EFFECTS OF INFECTION WITH A BABESIA-LIKE PIROPLASM, WA1,IN INBRED MICE

A newly identified intraerythrocytic Babesia-like organism, WA1, and i ts relatives were recently shown to be infectious for humans in the we stern United States. The purpose of the present study was to determine the susceptibilities of selected mouse genotypes to WA1 infection in an attempt to develop a murine model of the human disease, Several mou se strains were inoculated intraperitoneally with various passages of WA1-parasitized erythrocytes. Parasitemia was evaluated by blood smear s and by PCR with blood samples collected at various intervals after i noculation, Hematologic parameters were monitored in blood samples at all intervals. C57BL/6 and C57BL/10 mice exhibited mortality rates of < 10%. BALB/cJ, CBAJ, and 129/J mice had higher peak parasitemias than did C57BL mice, with mortality rates of 40, 50, and 50%, respectively , A/J, AKR/N, C3H, and DBA/1J mice also had higher peak parasitemia an d mortality rates (>95%), An F-1 cross of C57BL/6 (resistant) and C3H. RKK (susceptible) mice had a mortality rate similar to that of the res istant parental strain. Histopathology of BALB/cJ and C3H mice at 9 an d 14 days after inoculation revealed erythrophagocytosis and depositio n of an iron-negative pigment in multiple organs, Morbidly ill C3H mic e at 14 days had severe pulmonary edema, hemoglobinuria, and glomerulo nephritis.