Epidemiology and Molecular Characterisation of Blastocystis sp. in Nigeria

Abstract

Blastocystis sp. is a common intestinal protist with global distribution, yet data on its prevalence and genetic diversity in Northern Nigerian communities remain limited. This study aimed to determine the prevalence and identify the subtypes (STs) of Blastocystis sp. circulating in this region. In this cross-sectional community-based study, 551 stool samples were collected from asymptomatic residents of five villages in Kano State, Nigeria. Samples were analysed by direct smear microscopy. Microscopy-positive samples were then cultured in Jones’ medium, and subsequent molecular analysis was performed on positive cultures. This involved DNA extraction, PCR amplification of the small subunit ribosomal RNA (SSU-rRNA) gene, cloning, and sequencing to determine the subtypes. Microscopy revealed a Blastocystis prevalence of 29.2% (161/551), with higher infection rates in males and participants aged ≤15 years. Of the 161 microscopy-positive samples, 54 (32.3%) were successfully cultured and subtyped. Four subtypes were identified: ST1 (42.6%), ST3 (31.5%), ST4 (13%), and ST2 (7.4%). Three samples indicated mixed infections. ST1, ST3, and ST4 were more prevalent in male respondents, while all mixed infections were observed in males. The frequencies of all subtypes were generally higher in adults. Sequence analysis of cloned PCR products showed high homology with reference sequences in GenBank. This study confirms a high prevalence and genetic diversity of Blastocystis sp. in Northern Nigeria, with ST1 being the most dominant subtype. The occurrence of mixed infections highlights the complex epidemiology of this protist in the study population.