Pathology of experimental Babesia microti infection in the Syrian hamster

Pathologic changes produced after 4 weeks of infection by Babesia microti in Syrian hamsters are described and compared to babesiosis of humans. Following intraperitoneal inoculation, both intravascular and extravascular hemolysis developed. Up to 70% of red blood cells were parasitized. The principal morphologic abnormalities were an increase in extramedullary hematopoiesis and hyperplasia of the mononuclear phagocytic cells of the red pulp manifested grossly as splenomegaly, marked renal tubular hemosiderosis and hypertrophy of Kupffer cells. The disease was not fatal to any hamsters during the 4 week study. The clinical signs and lesions were less severe than fatal babesiosis of asplenic humans and similar to severe, but nonfatal disease in spleen intact humans. The hamster may serve as an animal model for the studying the pathophysiology of human babesiosis and for studying potential chemotherapeutic agents.