Feng Yaoyu, Ortega Ynes, He Guosheng, Das Pradeep, Xu Meiqian, Zhang Xichen, Fayer Ronald, Gatei Wangeci, Cama Vitaliano, Xiao Lihua
Division of Parasitic Diseases, Centers for Disease Control and Prevention, Atlanta, GA 30341, USA.
Vet Parasitol. 2007 Mar 15;144(1-2):1-9. doi: 10.1016/j.vetpar.2006.10.001. Epub 2006 Nov 13.
Recent studies in the United States reported that approximately 85% of pre-weaned dairy calves were infected with zoonotic Cryptosporidium parvum, whereas only 1-2% of post-weaned calves and 1-2-year-old heifers were infected with this species. Cryptosporidium bovis and Cryptosporidium deer-like genotype were much more prevalent in the post-weaned animals. It is not clear whether the same infection pattern also occurs in other geographic areas. In this study, to determine whether the same Cryptosporidium infection pattern was present in other geographic areas, we genotyped Cryptosporidium specimens collected from two farms in China and India, using specimens from farms in Georgia, USA for comparison. C. bovis was the most common species found in pre- and post-weaned calves in all three areas. In Georgia, the deer-like genotype was found frequently in pre- and post-weaned calves and Cryptosporidium andersoni was found in one post-weaned calf. Both C. bovis and the deer-like genotype were found in the few milking cows examined in Georgia. There were no differences in the small subunit rRNA gene sequences obtained from C. bovis or deer-like genotype among the three areas. One adult yak in China, however, was infected with a species similar to C. bovis, with only three nucleotide mutations in the target gene. All four common bovine Cryptosporidium spp. were differentiated from each other by restriction fragment length polymorphism analysis of PCR products with enzymes SspI and MboII. Thus, both C. bovis and the deer-like genotype are found in all age groups of cattle in diverse geographic areas and host adaptation of C. bovis might have occurred in yaks.
美国最近的研究报告称，约85%的断奶前奶牛犊感染了人畜共患的微小隐孢子虫，而断奶后犊牛和1 - 2岁小母牛中只有1 - 2%感染该物种。牛隐孢子虫和鹿样基因型隐孢子虫在断奶后动物中更为普遍。尚不清楚其他地理区域是否也存在相同的感染模式。在本研究中，为确定其他地理区域是否存在相同的隐孢子虫感染模式，我们对从中国和印度两个农场收集的隐孢子虫标本进行基因分型，并使用美国佐治亚州农场的标本进行比较。牛隐孢子虫是在所有三个区域断奶前和断奶后犊牛中发现的最常见物种。在佐治亚州，鹿样基因型在断奶前和断奶后犊牛中频繁发现，并且在一头断奶后犊牛中发现了安氏隐孢子虫。在佐治亚州检查的少数奶牛中同时发现了牛隐孢子虫和鹿样基因型。从三个区域的牛隐孢子虫或鹿样基因型获得的小亚基rRNA基因序列没有差异。然而，中国的一头成年牦牛感染了一种与牛隐孢子虫相似的物种，其目标基因仅有三个核苷酸突变。通过用SspI和MboII酶对PCR产物进行限制性片段长度多态性分析，可将所有四种常见的牛隐孢子虫物种相互区分开来。因此，牛隐孢子虫和鹿样基因型在不同地理区域的所有年龄组牛中均有发现，并且牛隐孢子虫可能已在牦牛中发生宿主适应性变化。
