Molecular Detection and Genetic Characterization of Colpodella spp. DNA in Human Fecal and Tick Samples from Hebei Province, China.

INTRODUCTION

Colpodella spp., a group of predatory protists closely related to the phylum Apicomplexa, are primarily known as free-living organisms associated with aquatic and terrestrial ecosystems. Although Colpodella-related DNA has increasingly been detected in vertebrate-associated samples, its distribution and ecological significance remain poorly understood. This study aimed to investigate the occurrence, molecular characteristics, and genetic diversity of Colpodella spp. DNA detected in human fecal samples and Haemaphysalis longicornis ticks from Hebei Province, China.

MATERIALS AND

METHODS

A total of 2,448 human fecal samples and 215 tick samples were collected from Hebei Province, China. The presence of Colpodella spp. DNA was investigated using PCR targeting the 18S rRNA gene, followed by sequencing, phylogenetic analysis, and genetic diversity assessment based on partial Colpodella spp. 18S rRNA sequences.

RESULTS

Colpodella spp. DNA was detected in 136 human fecal samples and 11 tick samples, with detection rates of 5.56% and 5.12%, respectively. Sanger sequencing successfully detected high-quality 18S rRNA sequences from all PCR-positive samples. Because identical sequences were detected among tick-derived samples, one representative sequence derived from H. longicornis ticks and 21 representative human-derived sequence types were selected for downstream analyses. Phylogenetic analysis based on 22 representative sequences showed that the sequences obtained in this study clustered within previously reported Colpodella spp. lineages. Genetic diversity analysis identified 3 haplotypes among the analyzed sequences.

CONCLUSIONS

This study provides molecular evidence for the occurrence and genetic variation of Colpodella spp. DNA in human fecal and tick-associated samples from Hebei Province, China. However, PCR-based detection alone cannot determine active infection, colonization, pathogenicity, or biological activity of the detected organisms. Further studies using additional molecular markers, culture systems, and biological approaches are required to clarify the ecological and potential health significance of Colpodella spp.