Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
Vet Parasitol. 2012 Apr 30;185(2-4):151-7. doi: 10.1016/j.vetpar.2011.09.030. Epub 2011 Sep 28.
A longitudinal herd-level study was carried out to determine the cumulative incidence of Giardia duodenalis infections in dairy cattle in the New York City Watershed. We also sought to assess the changes in infection pattern of animals diagnosed as shedding Giardia over time, determine risk factors that may be associated with G. duodenalis infections, and identify potentially zoonotic infections. A total of 2109 fecal samples were randomly collected from dairy cattle at 34 farms in the New York City Watershed on a seasonal basis. A total of 504 Giardia-positive samples were identified by zinc sulfate flotation. The overall cumulative incidence of G. duodenalis based on flotation results was 23.9% with 73.8% of all infections occurring in animals under 180 days of age (372/504). The intensity of infection ranged from 2 to 563,200 cysts/gram of feces. Cattle shedding Cryptosporidium spp. oocysts were twice as likely to shed G. duodenalis cysts in comparison to the animals that did not shed oocysts (1.81 95% CI 1.26-2.60 p=0.0012). In the multivariate analysis, only the age of the animal and the presence of dogs on the farm were significantly associated with the likelihood of shedding G. duodenalis. DNA was extracted from positive samples and analyzed by polymerase chain reaction (PCR) of the beta-giardin and triosephosphate isomerase genes of Giardia spp. 304 samples were analyzed by PCR of which 131 were sequenced. 22.1% of sequenced samples were identified as assemblage A and 77.9% were identified as assemblage E. Interestingly, 100% of specimens identified as assemblage A were from calves under 84 days of age indicating that younger cattle are important reservoirs for potentially zoonotic assemblages of G. duodenalis.
一项针对纽约市流域奶牛贾第鞭毛虫感染累积发病率的纵向群体研究。我们还试图评估随时间推移被诊断为排贾第虫的动物感染模式的变化，确定可能与贾第鞭毛虫感染相关的风险因素，并确定潜在的人畜共患病感染。我们在纽约市流域的 34 个农场按季节随机采集了 2109 份奶牛粪便样本。用硫酸锌漂浮法共检出 504 份贾第鞭毛虫阳性样本。根据漂浮结果，贾第鞭毛虫的总累积发病率为 23.9%，所有感染中有 73.8%发生在 180 天以下的动物（372/504）。感染强度范围从 2 到 563200 个囊/克粪便。与未排出卵囊的动物相比，排出隐孢子虫卵囊的牛排出贾第鞭毛虫囊的可能性高两倍（1.81 95%CI 1.26-2.60 p=0.0012）。在多变量分析中，只有动物的年龄和农场是否有狗与排出贾第鞭毛虫的可能性显著相关。从阳性样本中提取 DNA，用聚合酶链反应（PCR）分析贾第鞭毛虫的β-微管蛋白和磷酸丙糖异构酶基因。对 304 个样本进行了 PCR 分析，其中 131 个进行了测序。22.1%的测序样本被鉴定为 A 群，77.9%被鉴定为 E 群。有趣的是，100%鉴定为 A 群的标本均来自 84 天以下的小牛，这表明年龄较小的牛是潜在人畜共患的贾第鞭毛虫的重要储存宿主。
