Phylogenetic relationship of nonmammalian and avian Blastocystis isolates and conventional subtypes

Blastocystis is an intestinal protist commonly identified in human and animal feces. At present, there are 28 proposed subtypes (STs) identified based on the small subunit rRNA gene, 13 of which are found in both humans and animals. In general, nonmammalian and avian groups are infected by the nonmammalian and avian subtypes (NMASTs). However, NMASTs were also isolated from mammalian hosts, suggesting possible cross-contamination and transmission from nonmammalian and avian hosts to other animals and, potentially, humans. Thus, this study determined the possible relationship between NMAST sequences and conventional STs to provide new insights into Blastocystis classification, identification, and epidemiological significance. Phylogenetic trees were constructed using three statistical models, namely, Maximum Likelihood, Neighbor Joining, and Maximum Parsimony, based on the 30 NMAST sequences. The NMAST sequences formed groups clustered closely with other NMAST subtrees. Most sequences of nonmammalian and avian isolates formed distinct monophyletic clades based on their NMAST classification, with some clustering with mammalian and avian STs. These results indicate the close relationship between Blastocystis isolated from mammalian and avian hosts and nonmammalian and avian hosts.

The online version contains supplementary material available at (10.1007/s12639-022-01554-7).