Study of the population genetic structure of Opisthorchis-like eggs in northern Thailand using mitochondrial genes.

BACKGROUND

Opisthorchis-like eggs are a public health problem in northern and northeastern Thailand. However, the genetic epidemiology and structure of these parasites in northern Thailand are unknown. Thus, this study investigated their population genetic structure using cytochrome c oxidase subunit 1 (cox1) and NADH dehydrogenase subunit 1 (nad1) nucleotide sequences.

METHODOLOGY/PRINCIPAL FINDINGS: A study was conducted in the hill tribe regions of Chiang Mai Province, northern Thailand. Internal transcribed spacer 2 polymerase chain reaction and restriction fragment length polymorphism were used to distinguish 205 positive feces samples for Opisthorchis-like eggs. The results showed that the prevalence of O. viverrini and Haplorchis taichui was 10.5% and 38.2%, respectively, and the co-infection rate was 37.2%. To determine the genetic structure of O. viverrini and H. taichui using cox1 and nad1 genes, genetic analysis was performed using 30 randomly chosen fecal samples for Opisthorchis-like eggs. Pairwise FST analysis indicated that O. viverrini and H. taichui displayed nonsignificant genetic differentiation within Chiang Mai Province and between interpopulations from different geographic areas. Moreover, within the intrapopulation in Chiang Mai Province, cox1 presented higher gene flow than nad1 in O. viverrini, while nad1 demonstrated higher gene flow than cox1 in H. taichui. The neutrality tests based on Fu's Fs indicated population expansion and selective sweep from bottleneck or hitchhiking in O. viverrini and H. taichui populations, supported by haplotype network patterns. Phylogenetic tree analysis based on cox1 and nad1 revealed the monophyly of O. viverrini and H. taichui and genetic relationships with other isolates collected from Thailand, Lao People's Democratic Republic (PDR), and Vietnam.

CONCLUSIONS/SIGNIFICANCE: This study investigated the molecular discrimination and genetic structure of Opisthorchis-like eggs in northern Thailand. The genetic information derived from this study could be associated with the background, molecular epidemiology, and disease severity of these parasites.