A novel dual-locus genotyping approach reveals epidemiological characteristics of Balantioides coli in intensive pig farms

Balantioides coli is a significant zoonotic parasitic protozoan, with pigs serving as its reservoir host. The limited molecular typing tools for B. coli have hindered understanding of its transmission and genetic variability in intensive pig farming. In this study, 1251 pig fecal samples were collected in two batches from three intensive farms. A dual-locus molecular typing method based on the β-tubulin and ITS genes was developed and applied to analyze the epidemiological characteristics and genetic variability of B. coli . The results revealed an overall infection rate of 87.7% (1097/1251), with an age-dependent pattern where lower rates were observed in 1–2-month-old piglets, followed by a rapid increase at 3–4 months, and near 100% prevalence by 5–6 months. Phylogenetic analysis based on the β-tubulin gene delineated three haplotypes (I, II, and III), confirming the previously identified ITS sequence variants A and B, and further resolving the novel sequence variant C. The expression of haplotypes and sequence variants showed a marked geographical distribution pattern, with haplotype I and variant A predominantly concentrated in the Zhejiang region, while haplotype III and variant C were detected in pigs and exclusively found in this area. These findings indicate that B. coli transmission is highly prevalent under intensive, high-density rearing conditions, and that the distribution of certain sequence variants shows geographical clustering, which may reflect local ecological or husbandry factors. This study provides important dual-locus genotyping insights for elucidating the transmission mechanisms of B. coli within intensive farming systems.