Diversity and host specificity of Blastocystis in syntopic primates on Rubondo Island, Tanzania.

The isolated ecosystem of Rubondo Island National Park, Tanzania is an interesting model site, inhabited by an assembly of primate species with various histories: two introduced primate species, Pantroglodytes (chimpanzee) and Colobus guereza (colobus), and a single indigenous species Chlorocebus aethiops pygerythrus (vervet monkey). Apart from important lessons for future introduction/re-introduction projects, Rubondo National Park offers a unique place to study the patterns of transmission of primate parasites and their host specificity. Blastocystis was detected using standard microscopy, together with PCR-based determination and the prevalence and subtype identification of Blastocystis was determined in each primate species. Subtype (ST) 1 was detected in all three Rubondo primate populations; ST2, ST3 and ST5 were found in colobus and vervet monkeys. All chimpanzee isolates of Blastocystis belonged exclusively to ST1, which formed a discrete group, suggesting that Rubondo chimpanzees are colonized by a single, host-specific Blastocystis strain that circulates among the members of the group. Phylogenetic analysis indicated that transmission of Blastocystis did not occur between Rubondo primate populations. Observed host specificity of Blastocystis provides a new understanding of the transmission and distribution of Blastocystis among sympatric hosts under natural conditions.