Abstract
BACKGROUND: Cryptosporidium spp. and Giardia duodenalis are important causes of diarrheal diseases in humans and animals worldwide, and there is an increased interest in the role of animals in the mechanical transmission of these protozoa. To examine the role of yaks in this process, we examined the occurrence and genotypes of Cryptosporidium and G. duodenalis in yaks in western China. RESULTS: A total of 545 fecal specimens were collected from yaks from nine different counties in the central western region of China. The prevalence for Cryptosporidium spp. and G. duodenalis were 4.0 % (22/545) and 6.0 % (16/545), respectively. Mixed infections of Cryptosporidium and G. duodenalis were also detected in four specimens. The prevalence of both protozoa differed significantly between some age groups, with higher rates of infection in animals < 1 year old. Sequence analysis of the small subunit rRNA (SSU rRNA) gene of the Cryptosporidium isolates identified the species as C. parvum (n = 12), C. bovis (n = 6), C. ryanae (n = 3), and C. ubiquitum (n = 1). Genotyping based on 60-kDa glycoprotein (gp60) gene from five C. parvum isolates identified all as IId with three isolates identified as IIdA15G1, one as IIdA18G1, and one as IIdA19G1. One C. ubiquitum isolate was identified as subtype VIIa. Amongst the G. duodenalis isolates, 16 were identified as assemblage E at the SSU rRNA gene. Four novel glutamate dehydrogenase (gdh) subtypes and two triosephosphate isomerase (tpi) subtypes were found amongst the G. duodenalis assemblage E isolates. CONCLUSIONS: The presence of C. parvum subtype IIdA15G1, IIdA18G1, and IIdA19G1 isolates further confirms the dominance of the C. parvum IId subtypes in China. These findings also indicate that yaks may be a source of zoonotic Cryptosporidium infection, and this is the first report of G. duodenalis in yaks. The data presented here provides the basis for further genotyping or subtyping studies of G. duodenalis in yaks.