Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, 550 University Ave., Charlottetown, PE, C1A 4P3, Canada.
Vet Parasitol. 2012 Feb 28;184(1):1-9. doi: 10.1016/j.vetpar.2011.10.027. Epub 2011 Oct 25.
The objectives of this study were to determine the prevalence and assemblages of Giardia and species of Cryptosporidium on beef farms in Prince Edward Island (PEI), Canada, including the water sources associated with the farms, and to determine risk factors for infection of cattle with these parasites. Twenty beef farms were selected based on the presence of surface water< 500 m from the barn. Prevalence was determined by direct immunofluorescence microscopy, while genotyping and species determination were performed by nested-PCR and DNA sequencing. Giardia was detected in 42% (95% CI: 38-46%) of fecal samples from 100% farms while Cryptosporidium was detected in 17% (95% CI: 14-19%) of fecal samples from 80% of farms. The most predominant Giardia assemblage isolated was the livestock specific assemblage E (89%). The zoonotic assemblages A and B were found in 4 and 7% of the Giardia isolates that were genotyped, respectively. The Giardia assemblages were detected equally between the cows and calves examined. Overall, the most common Cryptosporidium species detected in this study was Cryptosporidium andersoni (49%), predominantly found in cattle > 6 mo of age, while most Cryptosporidium bovis and Cryptosporidium pestis (previously Cryptosporidium parvum 'bovine genotype') isolates were detected in calves ≤ 6 mo of age. All Cryptosporidium ryanae isolates (four) were found in calves. Giardia cysts and Cryptosporidium oocysts were detected in 14 and 93% of surface water samples of 14 farms, respectively. Cryptosporidium oocysts were detected in three (15%) ground water samples of 20 farms. One Cryptosporidium-positive water sample, which was the only surface water sample amenable to genotyping, contained C. parvum. The farm-level risk factors investigated in this study, age of animals and location of the farm, were not associated with the risk of infection in cattle with either Cryptosporidium spp. or Giardia duodenalis. We conclude that beef cattle are a potential reservoir of Cryptosporidium spp. and G. duodenalis that could contaminate source water. There is the possibility of further transmission to humans on PEI if the source water is not properly treated prior to consumption.
本研究的目的是确定加拿大爱德华王子岛（PEI）的肉牛养殖场（包括与农场相关的水源）中贾第虫和隐孢子虫的流行率和虫种组成，并确定这些寄生虫感染牛的风险因素。根据牛舍 500 米以内地表水的存在，选择了 20 个肉牛养殖场。通过直接免疫荧光显微镜法确定流行率，通过巢式 PCR 和 DNA 测序进行基因分型和种属鉴定。从 100%的农场采集的粪便样本中，42%（95%CI：38-46%）检测到贾第虫，80%的农场采集的粪便样本中 17%（95%CI：14-19%）检测到隐孢子虫。分离出的最主要的贾第虫虫种是家畜特异性虫种 E（89%）。在进行基因分型的贾第虫分离株中，分别发现了 4%和 7%的人兽共患虫种 A 和 B。在检查的牛和小牛中，贾第虫虫种的检出率相等。总体而言，本研究中最常见的隐孢子虫种是隐孢子虫和ersoni（49%），主要发现于 6 月龄以上的牛，而大多数隐孢子虫 bovis 和隐孢子虫 pestis（以前称为隐孢子虫 parvum '牛基因型'）分离株见于 6 月龄以下的小牛。所有的隐孢子虫 ryanae 分离株（4 株）均在小牛中发现。在 14 个农场的 14 个地表水样本中分别检测到贾第虫囊和隐孢子虫卵囊，在 20 个农场的 3 个地下水样本中检测到隐孢子虫卵囊。本研究中调查的农场级风险因素，即动物的年龄和农场的位置，与牛感染隐孢子虫 spp.或十二指肠贾第虫的风险无关。我们得出结论，肉牛是隐孢子虫和十二指肠贾第虫的潜在储存宿主，可能会污染水源。如果在饮用水之前没有对水源进行适当的处理，PEI 上的人类有进一步传播的可能性。
