Bureau of Microbial Hazards, Health Canada, 251 Sir Frederick Banting Driveway, P.L. 2204E, Ottawa, Ontario, Canada.
Vet Parasitol. 2011 Jan 10;175(1-2):20-6. doi: 10.1016/j.vetpar.2010.09.032. Epub 2010 Oct 7.
The objective of this study was to compare the occurrence and the genotypes and species of Giardia duodenalis and Cryptosporidium spp. in beef and dairy cattle from farms in the Regional Municipality of Waterloo, Ontario, in an effort to determine the potential for zoonotic transmission from these animals. Pooled manure samples were collected from 45 dairy cattle farms and 30 beef cattle farms. The presence of Giardia cysts and Cryptosporidium oocysts was determined by immunofluorescence microscopy, while nested-PCR and DNA sequencing were used to determine genotypes and species. The overall farm prevalence was very high for both Giardia and Cryptosporidium, and was similar for dairy cattle farms (96 and 64%, respectively) and beef cattle farms (97 and 63%, respectively). However, on dairy cattle farms, G. duodenalis and Cryptosporidium spp. were detected in 44% and 6% of total pooled pen manure samples, respectively, with the occurrence of both parasites being generally higher in calves than in older animals. Most Giardia isolates were identified as either the host-adapted genotype G. duodenalis Assemblage E or the zoonotic Assemblage B. Cryptosporidium parvum and Cryptosporidium andersoni were the most frequently identified species in dairy cattle, while the non-zoonotic species Cryptosporidium ryanae and Cryptosporidium bovis were also found. On beef cattle farms, 72% and 27% of the total pooled pen manure samples were positive for Giardia and Cryptosporidium, respectively, with no obvious correlation with age. All Giardia isolates in beef cattle were identified as G. duodenalis Assemblage E, while all Cryptosporidium isolates were identified by sequence analysis as C. andersoni, although microscopic analyses, and subsequent restriction fragment length polymorphism analyses, indicated that other Cryptosporidium species were also present. The results of this study indicate that although Giardia and Cryptosporidium were identified in a higher overall percentage of the pooled beef cattle manure samples than in dairy cattle, firmly established zoonotic genotypes and species were much more common in dairy cattle than in beef cattle in this region. Dairy cattle, and especially dairy calves, may, therefore, pose a greater risk of infection to humans than beef cattle. However, these results may also provide evidence of potential zooanthroponotic transmission (human to animal).
本研究的目的是比较安大略省滑铁卢地区农场的肉牛和奶牛中肠道贾第虫和隐孢子虫的发生情况和基因型及种型，以确定这些动物传播给人类的潜在可能性。从 45 个奶牛场和 30 个肉牛场采集了混合粪便样本。通过免疫荧光显微镜检查确定了贾第虫包囊和隐孢子虫卵囊的存在，而巢式 PCR 和 DNA 测序用于确定基因型和种型。贾第虫和隐孢子虫的总体农场流行率非常高，奶牛场和肉牛场的流行率分别为 96%和 64%。然而，在奶牛场，在 44%的总混合畜栏粪便样本中检测到了 G. duodenalis，在 6%的样本中检测到了隐孢子虫，通常幼畜的寄生虫发生率高于成年动物。大多数贾第虫分离株被鉴定为宿主适应性基因型 G. duodenalis 集合 E 或人畜共患的集合 B。在奶牛中，最常鉴定到的隐孢子虫种是小隐孢子虫和人隐孢子虫，而非人畜共患的隐孢子虫种赖氏隐孢子虫和牛隐孢子虫也被发现。在肉牛场，72%和 27%的总混合畜栏粪便样本分别对贾第虫和隐孢子虫呈阳性，与年龄无明显相关性。在肉牛中，所有贾第虫分离株均被鉴定为 G. duodenalis 集合 E，而所有隐孢子虫分离株均通过序列分析鉴定为人隐孢子虫，尽管显微镜分析和随后的限制性片段长度多态性分析表明，还存在其他隐孢子虫种。本研究结果表明，尽管在混合肉牛粪便样本中，贾第虫和隐孢子虫的检出率总体上高于奶牛，但在该地区，奶牛中更常见的是牢固确立的人畜共患基因型和种型。因此，与肉牛相比，奶牛，特别是奶牛犊，可能对人类的感染风险更大。然而，这些结果也可能提供了潜在的动物源性人畜共患病传播（人类到动物）的证据。
