Blastocystis hominis in animals: incidence of four serogroups.

In toto, 520 faecal samples from mammals, birds, reptiles, amphibians, fish, and snails were investigated (see Table 1). 91 strains of Blastocystis hominis could be isolated by culture. However, only 48 of them were suitable for axenisation. 96 percent of samples belonged to four serogroups detected in humans but two strains, one from a pig and another from a duck, could not be classified, suggesting the existence of one or two further serogroups. While humans showed mainly serogroups I and II, pigs harboured serogroups III and IV. Four serogroups were isolated from monkeys. The question whether the genus Blastocystis consists of one or more species is discussed.