Comparison of geographical strains of Schistosoma mansoni in the mouse.

Mice were killed 7, 11, 19, and 27 weeks after infection with strains of Schistosoma mansoni from Puerto Rico, Brazil, St Lucia, and Tanzania. The percentage recovery of adult worms was variable in different experiments and no consistent strain differences were observed. The prepatent period was prolonged in mice infected with the Mwanza strain. Significant differences were noted in the number of eggs per worm pair in the tissues, in the distribution of eggs in the tissues, and in the weight of the liver of mice infected with different strains. No differences in hepatic histopathology were detected. Although the behaviour of various worm strains in this mammalian host is clearly different, we feel that the observed differences are trivial when considering the effects of the parasite on the host, and that the results in mice probably cannot be used to predict possible differencesin the behaviour of geographical strains of S. mansoni in infected persons.