Extrahepatic pathology in rabbits infected with Japanese and Philippine strains of Schistosoma japonicum, and the relation of intestinal lesions to passage of eggs in the feces.

A Japanese strain of Schistosoma japonicum produced segmental circumferential lesions 15-40 cm in length in the proximal jejuum of infected rabbits, while a Philippine strain of the parasite produced small numbers of focal nodular lesions (bilharziomas) in the colon. Sequestration of large numbers of schistosome eggs in these latter lesions apparently accounted for the small and erratic number of S. japonicum eggs passed in the feces of rabbits infected with the Philippine strain. These focal masses also illustrate dramatically the gregarious nature of schistosome worm pairs, all of which concentrated in two or three focal lesions, leaving essentially normal bowel elsewhere. Sandy patches were frequently seen in the bowel in sites of heavy egg deposition, and calcified eggs were evident radiologically. The fibrotic response to schistosome egg deposition was marked in the liver. In contrast, the collagen content of the intestine was nearly normal in animals infected with the Philippine strain and only moderately increased in rabbits infected with the Japanese strain. Numerous eggs and granulomas were present in the lungs, but fibrosis of pulmonary granulomas was minimal.