The host-parasite relationship of Schistosoma japonicum in CBA mice.

The host-parasite relationship of the Chinese mainland strain of Schistosoma japonicum in CBA mice is described and compared to previous reports on this parasite in mice. S. japonicum took under 2 weeks to complete its migration to the portal system of mice, and peak passage of schistosomula through the lungs occurred 5-6 days after infection. The mean percentage establishment of worms, which was independent of the infecting inoculum, was 46%. The adult worm burdens remained constant over a 28-week period of infection. Male and female worms reached maximum mean lengths of 13 and 19 mm, respectively. Egg laying commenced 30 days after infection. The number of ova deposited in the liver stabilized at some 55 000 by 12 weeks of infection with 30 cercariae, but the intestinal egg burden rose from 132 000 at 12 weeks to 430 000 at 28 weeks. Faecal eggs were first observed 6 weeks after mice were exposed to 100 cercariae and 7 weeks after lighter exposures. Faecal egg output also stabilized 12 weeks after infection. The formation of granulomas in the liver occurred within 2 weeks of egg deposition and encompassed a maximum area 14 weeks after infection. Fifty per cent mortality occurred 15 weeks after exposure, but only in hosts infected with 100 cercariae.