The infection characteristics of a South African isolate of Schistosoma mansoni: a comparison with a Puerto Rican isolate in BALB/c mice and Mastomys coucha.

The infection characteristics of a South African (RSA) laboratory isolate of Schistosoma mansoni were compared with those of a widely studied Puerto Rican (PR) isolate in BALB/c mice and Mastomys coucha over the period of 5-12 weeks after infection. The infectivity, maturation and, in particular, the fecundity of the two schistosomes were found to differ markedly. Tissue egg-accumulation rates of the RSA strain were substantially lower than those of the PR strain. Although the maturation of both parasite strains was somewhat delayed in M. coucha, the characteristics of each was essentially consistent in both rodent hosts. Notwithstanding the possible influence of prolonged laboratory passage on the behaviour of schistosome isolates, the results of the present study are nevertheless considered to support the idea that parasite strain differences may, to some extent, account for regional variations in the morbidity of intestinal schistosomiasis. The need to be cognizant of the characteristics of individual host-parasite combinations when comparing different schistosome species and strains, particularly with respect to both their abilities to elicit immunopathology and induce concomitant immunity and their susceptibilities to chemotherapy, is highlighted.