National Microbiology Laboratory, Public Health Agency of Canada, Guelph, Ontario N1G 3W4, Canada.
National Microbiology Laboratory, Public Health Agency of Canada, Guelph, Ontario N1G 3W4, Canada.
Vet Parasitol Reg Stud Reports. 2022 Sep;34:100777. doi: 10.1016/j.vprsr.2022.100777. Epub 2022 Aug 17.
Cryptosporidium is a zoonotic protozoan parasite that is distributed globally and impacts both human and animal health. There are over 40 species of Cryptosporidium described to date, of which four (C. parvum, C. bovis, C. ryanae and C. andersoni) are routinely reported in cattle. The goal of this study was to identify the Cryptosporidium species infecting dairy cattle from across Canada using cow fecal samples and post-weaned calf rectal swabs obtained through the Canadian National Dairy Study. A total of 353 cattle samples (117 pooled rectal fecal swabs from post-weaned calves and 236 cow fecal samples) from 175 herds across the 10 Canadian provinces were analysed by targeting Cryptosporidium's small subunit ribosomal RNA (SSU rRNA or 18S) gene. Herd prevalence of Cryptosporidium was 27.4% nationally, ranging from 0% in Saskatchewan (SK) to 62% in Prince Edward Island (PE). The national prevalence of Cryptosporidium cattle infections was 15.4% in pooled rectal fecal swab samples from post-weaned calves and 16.1% in adult cows. Sanger sequence analysis of the SSU rRNA gene target revealed that C. bovis, C. andersoni and C. ryanae occurred in both adults and post-weaned calves, with C. bovis as the predominant species detected in pooled fecal swab samples of post-weaned calves (9/18, 50%) and C. andersoni as the predominant species in cows (25/38, 66%). Cryptosporidium parvum was not observed in any of the pooled rectal swab samples from post-weaned calves but was observed in one mixed infection of C. bovis/C. parvum in an adult cow. The fifth species identified in this study was C. muris and was present in two adult cows. Low concentrations of oocyst equivalents, as measured by quantitative real-time PCR (qPCR) of the SSU rRNA gene copy number, were observed in a subset of cattle samples. Cryptosporidium andersoni concentrations varied from province to province, with the widest range and highest counts in cows from PE. In conclusion, oocysts from Cryptosporidium species observed in this study are shed into the environment, contributing to the environmental load. However, the Cryptosporidium species in the post-weaned calves and cows found in this study pose a lower risk to the dairy cattle than if they were infected with C. parvum. Similarly, these Cryptosporidium species pose only a small risk to public health as the three species are infrequently reported in humans globally and have not been reported in Canadians to date.
隐孢子虫是一种全球性分布的动物源性原生动物寄生虫，对人类和动物健康均有影响。迄今为止，已描述了超过 40 种隐孢子虫，其中 4 种（小隐孢子虫、牛隐孢子虫、里氏隐孢子虫和安氏隐孢子虫）在牛群中经常被报道。本研究的目的是使用加拿大国家奶牛研究中获得的牛粪便样本和断奶后小牛直肠拭子，从加拿大各地的奶牛中鉴定出感染隐孢子虫的种类。共分析了来自加拿大 10 个省 175 个牛群的 353 个牛粪便样本（117 个断奶后小牛直肠粪便混合样本和 236 个牛粪便样本），这些样本均针对隐孢子虫的小亚基核糖体 RNA（SSU rRNA 或 18S）基因进行了目标分析。隐孢子虫在全国的畜群流行率为 27.4%，萨斯喀彻温省（SK）为 0%，爱德华王子岛（PE）为 62%。断奶后小牛直肠粪便混合样本中隐孢子虫牛感染的全国流行率为 15.4%，成年牛为 16.1%。SSU rRNA 基因靶标的 Sanger 序列分析显示，牛隐孢子虫、安氏隐孢子虫和里氏隐孢子虫存在于成年牛和断奶后小牛中，牛隐孢子虫是断奶后小牛粪便混合样本中检测到的主要种（18 份样本中的 9 份，50%），而安氏隐孢子虫是成年牛中的主要种（38 份样本中的 25 份，66%）。在任何断奶后小牛的直肠拭子样本中均未观察到小隐孢子虫，但在一头成年母牛的混合感染中观察到了小隐孢子虫。本研究中鉴定的第五种是鼠隐孢子虫，存在于两头成年牛中。通过 SSU rRNA 基因拷贝数的定量实时 PCR（qPCR）测量，在一小部分牛样本中观察到低浓度卵囊等价物。安氏隐孢子虫的浓度因省份而异，PE 的牛中浓度范围最广，数量最高。综上所述，本研究中观察到的隐孢子虫种释放到环境中，增加了环境负荷。然而，与感染小隐孢子虫相比，本研究中在断奶后小牛和奶牛中发现的隐孢子虫种对奶牛的风险较低。同样，由于这三种隐孢子虫在全球范围内很少在人类中报告，并且迄今为止在加拿大也没有报告，因此这些隐孢子虫种对公众健康的风险很小。
