Genetic Characterization and Zoonotic Potential of <i>Cryptosporidium</i> spp. and <i>Giardia duodenalis</i> in Cattle From Northeast China

Cryptosporidium spp. and Giardia duodenalis ( G. duodenalis ) are zoonotic and gastrointestinal parasites infecting humans and animals. This study investigated the prevalence and subtypes of Cryptosporidium and G. duodenalis in cattle from six farms across three provinces and one autonomous region in northeast China. Fecal samples ( n = 495) were detected using PCR‐based methods: Cryptosporidium was genotyped via PCR‐restriction fragment length polymorphism (RFLP) targeting the small subunit ribosomal RNA ( SSU rRNA) gene, and G. duodenalis assemblages were identified through multilocus sequence typing of the β ‐giardin ( bg ), glutamate dehydrogenase ( gdh ), and triose phosphate isomerase ( tpi ) genes. Overall infection rates were 44.44% (220/495) for Cryptosporidium and 39.39% (195/495) for G. duodenalis . Age‐related trends showed Cryptosporidium prevalence peaked in preweaned calves (63.29%, 50/79), whereas the highest prevalence rate of G. duodenalis infections (53.66%, 66/123) was observed in calves aged 3–11 months. Four Cryptosporidium species ( C. parvum , C. bovis , C. ryanae , and C. andersoni ) and coinfections involving two or three Cryptosporidium species were identified. Based on 60‐kilodalton glycoprotein ( gp60 ) gene of C. parvum , three subtypes (IIdA19G1, IIdA24G2, and IIdA21G1) were identified. Subtype IIdA21G1 was reported for the first time in cattle, with its initial detection occurring in China. For G. duodenalis , assemblages A and E were identified in all four areas, with 13 assemblage E multilocus genotypes (MLGs), one assemblage A MLG, and eight mixed (A + E) MLGs detected. Our findings revealed a novel genetic subtype of C. parvum in China, and the high prevalence of both Cryptosporidium and G. duodenalis suggested an increased zoonotic risk that deserved more attention.