Zoonotic Transmission Assessment of <i>Cryptosporidium</i> spp. in Close Human–Pet Environments in Yunnan Province, China

BACKGROUND: Investigation on Cryptosporidium transmission between pets and their close human contacts remains limited. OBJECTIVE: Here, we assessed Cryptosporidium prevalence in companion animals and their contacts. METHODS: Faecal samples from dogs and cats (n = 352) and associated humans (n = 108) were screened by nested PCR targeting the SSUrRNA gene, and the positive specimens were subtyped by sequencing the 60-kDa glycoprotein gene (gp60). RESULTS: The infection rates of Cryptosporidium spp. were 11.1% in dogs and 10.4% in cats, and dogs with diarrhoea were more likely to be infected by Cryptosporidium spp. (47.8%; odds ratio [OR] = 14.3, p = 0.001). Among human specimens, only a 62-year-old owner who had long-term contact with rescued stray cats tested positive for Cryptosporidium spp. Cryptosporidium canis was detected in dogs, and Cryptosporidium felis was detected in cats and the owner. The C. canis isolates comprised both zoonotic (XXa and XXb) and dog-adapted (XXd and XXe) subtypes, whereas all C. felis isolates clustered within zoonotic subtype family XIXa. Notably, the C. felis isolates from the owner and the two cats were found to have an identical gp60 sequence to a known human subtype XIXa-40. In addition, young dogs shed significantly more C. canis oocysts per gram of faeces (4000) than adult dogs (∼2000). CONCLUSIONS: Our results showed that transmission of pet cryptosporidiosis to adults was minimal, but spillover to immunocompromised elderly individuals could pose a public health concern.