Prevalence and Genetic Characterization of Giardia duodenalis and Blastocystis sp. in Horses in Shanxi Province, North China.

Giardia duodenalis (synonyms G. lamblia and G. intestinalis) and Blastocystis sp. are prevalent zoonotic intestinal protozoans with significant public health and economic importance. Both parasites infect various hosts, including humans and most livestock. G. duodenalis can cause infections ranging from asymptomatic carriage to clinical manifestations such as acute diarrheal disease, growth stunting and malabsorption, whereas Blastocystsi sp. infection is often asymptomatic and its pathogenicity remains debated. Following the rapid expansion of modern equine industries (horse racing, equestrian sports, production, and tourism), concern about the spread of parasitic diseases caused by human-horse contact has gradually increased. In this study, 631 horse fecal specimens were collected from three geographical localities in Shanxi Province, North China. The prevalence and genetic characteristics of the two parasites were determined by amplification of multiple genetic loci (tpi, triosephosphate isomerase; gdh, glutamate dehydrogenase; bg, beta-giardin) for G. duodenalis and the small subunit ribosomal RNA (SSU rRNA) gene for Blastocystis sp. Overall, the prevalence of G. duodenalis and Blastocystis sp. in horses in Shanxi Province was 7.9% and 0.8%, respectively. Sequence analysis identified three assemblages (A, B, and E) of G. duodenalis and two subtypes (ST1 and ST5) of Blastocystis sp. in horses; assemblage B and subtype ST1 were detected more frequently than the other types (subtypes) in this data set. This study is the first to report G. duodenalis and Blastocystis sp. infections in horses in Shanxi Province, and these findings provide baseline molecular epidemiological data for horses in Shanxi Province and support continued hygiene management to reduce potential zoonotic transmission.