Subtype Identification of Blastocystis sp. Among Humans and Domestic Animals in the West of Iran

Blastocystis is a genetically diverse intestinal protozoan found in a wide range of human and animal hosts. The present study was conducted to identify the subtypes of Blastocystis in both humans and animals in Kermanshah province, Iran.

A total of 820 stool samples from humans, cattle, sheep, and pigeons were examined using the formalin-ethyl acetate concentration method. All isolates were cultured in clotted fetal bovine serum medium. DNA extraction, PCR amplification and sequencing were performed targeting an identical fragment of the small subunit ribosomal RNA (SSU rRNA) gene. Phylogenetic tree and haplotype network were conducted by MEGA6 and PopART software. Data analysis was performed by Chi-square and Fisher's exact tests, while a p value of < 0.05 was considered as statistically significant.

Totally, Blastocyctis was found in 9.1% and 4.5% of human samples using microscopy and growing in culture medium, respectively. A significant association was observed between Blastocystis infection and both age and gastrointestinal symptoms. Two subtypes of ST2 and ST5 were identified in humans and livestock (cattle and sheep), respectively. The results of haplotype analysis showed clear classification of two groups and six haplotype (Group I and II) in the isolates.

This study highlights the zoonotic potential of Blastocystis species in the studied region. The subtype distribution may inform preventive strategies and help elucidate transmission routes. Additionally, further research is needed to fully understand the pathogenic potential of this parasite.