PATHOLOGY OF ACUTE FATAL BABESIOSIS IN HAMSTERS EXPERIMENTALLY INFECTED WITH THE WA-1 STRAIN OF BABESIA

A strain of Babesia (strain WA-1), recently isolated from a human in W ashington State, was found to be unusually virulent for hamsters; it c aused acute infection and death in a large proportion of animals 5 to 7 days after inoculation. To assess the basic pathologic lesions assoc iated with this infection, 30 male Syrian hamsters (Mesocricetus aurat us) were inoculated intraperitoneally with the WA-1 strain. Twelve ani mals (40%) died within 5 to 6 days. The other 18 animals, all infected and clinically ill, were killed on the sixth or seventh day for bioch emical study. All 12 animals that died from the infection showed high parasitemia, heavy intravascular hemolysis, and pronounced vascular st asis with red-cell sequestration in the spleen, liver, lungs, kidneys, and brain. Serologic study revealed severe anemia (mean hematocrit, 2 9) with hemolyzed serum and marked elevation of the serum transaminase s. The mechanism of death was thought to be diffuse anoxic tissue dama ge secondary to vascular stasis, which led to multiorgan failure.