Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases and Laboratory of Statistical, Mathematical Methodology, Division of Computer Research and Technology, National Institutes of Health, Bethesda, Maryland 20205
Sixty-seven rabbits were killed 8–66 weeks after infection with a Japanese strain of Schistosoma japonicum and 22 were killed 12–55 weeks after infection with a Philippine strain. Worm numbers decreased moderately over the course of infection and the number of eggs laid by each worm pair also decreased, as evidenced by decreasing numbers of mature (viable) eggs per worm pair in the tissues and, for the Japanese strain, by decreasing numbers of eggs per worm pair passed in the feces. Many eggs calcified in the tissues and the number of eggs per worm pair found in the tissues increased with time in a nearly linear fashion. For both schistosome strains, the total number of eggs in the tissues was proportional to the number of worms present at any given time. The number of eggs passed in the feces correlated well with the number of worm pairs present in rabbits infected with the Japanese strain, but in rabbits infected with the Philippine strain the few eggs passed in the feces correlated poorly with the intensity of infection. Worms of the Japanese strain were located primarily in venules of the proximal jejunum and those of the Philippine strain primarily in venules of the colon.