United States Department of Agriculture, Agricultural Research Service, Environmental Microbial Food Safety Laboratory, Beltsville, MD 20705, USA.
Vet Parasitol. 2010 Jun 24;170(3-4):187-92. doi: 10.1016/j.vetpar.2010.02.040. Epub 2010 Mar 3.
To determine the species and distribution of Cryptosporidium in weaned beef calves in the United States, fecal specimens were collected from 819 cattle between 6 and 18 months of age from 49 operations in 20 states (Alabama, California, Colorado, Georgia, Idaho, Iowa, Kansas, Louisiana, Mississippi, Missouri, Nebraska, New Mexico, North Dakota, Oklahoma, Oregon, South Dakota, Tennessee, Texas, Virginia, and Wyoming). Fresh feces, collected either from the ground or directly from the rectum of each animal, were sieved and subjected to density gradient centrifugation to remove fecal debris and to concentrate oocysts. DNA extracted from each specimen was subjected to the polymerase chain reaction (PCR) using primers for the SSU rRNA gene. All PCR positive specimens were subjected to sequence analysis. Cryptosporidium was detected in 20.5% of the fecal samples. Cryptosporidium ryanae, C. bovis and C. andersoni were detected in 1.8, 4.8, and 14.0% of the 819 samples, respectively. California (number operations [n]=2), Iowa (n=3), and Nebraska (n=7) had the highest prevalence of infected weaned cattle with 44.4, 41.0 and 40.2% infected, respectively. Cryptosporidium was not detected in any weaned cattle from Alabama (number operations [n]=1), Georgia (n=2), New Mexico (n=1), South Dakota (n=1), Tennessee (n=1), or Texas (n=1). The zoonotic species, C. parvum, was not detected in any samples from 6- to 18-month-old cattle, a finding that parallels reports for dairy cattle of similar age in which less than 1% were found to harbor this species.
为了确定美国断奶肉牛中隐孢子虫的种类和分布，从 20 个州（阿拉巴马州、加利福尼亚州、科罗拉多州、佐治亚州、爱达荷州、爱荷华州、堪萨斯州、路易斯安那州、密西西比州、密苏里州、内布拉斯加州、新墨西哥州、北达科他州、俄克拉荷马州、俄勒冈州、南达科他州、田纳西州、得克萨斯州、弗吉尼亚州和怀俄明州）的 49 个养殖场中，采集了 819 头 6-18 月龄牛的粪便样本。采集新鲜粪便，或直接从每只动物的直肠中采集，将其过筛并进行密度梯度离心，以去除粪便碎屑并浓缩卵囊。从每个样本中提取的 DNA 都用 SSU rRNA 基因的引物进行聚合酶链反应（PCR）。所有 PCR 阳性样本均进行序列分析。在 20.5%的粪便样本中检测到隐孢子虫。在 819 个样本中，分别检测到 1.8%、4.8%和 14.0%的兰氏贾第虫、牛隐孢子虫和牛安氏隐孢子虫。加利福尼亚州（操作次数[n]=2）、爱荷华州（n=3）和内布拉斯加州（n=7）的感染断奶牛比例最高，分别为 44.4%、41.0%和 40.2%。在阿拉巴马州（操作次数[n]=1）、佐治亚州（n=2）、新墨西哥州（n=1）、南达科他州（n=1）、田纳西州（n=1）或得克萨斯州（n=1）的断奶牛中均未检测到隐孢子虫。在 6-18 月龄牛的任何样本中均未检测到人畜共患种 C. parvum，这与类似年龄的奶牛的报告结果相似，在这些奶牛中，不到 1%的奶牛携带该种。
