Division of Foodborne, Waterborne and Environmental Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, 1600 Clifton Rd, Atlanta, GA, USA; Department of Zoology, Faculty of Science, Kafr El Sheikh University, Kafr El Sheikh 33516, Egypt.
Exp Parasitol. 2013 Nov;135(3):518-23. doi: 10.1016/j.exppara.2013.09.002. Epub 2013 Sep 13.
Molecular characterizations of Cryptosporidium spp. in dairy cattle in industrialized nations have mostly shown a dominance of Cryptosporidium parvum, especially its IIa subtypes in pre-weaned calves. Few studies, however, have been conducted on the distribution of Cryptosporidium species and C. parvum subtypes in various age groups of dairy cattle in developing countries. In this study, we examined the prevalence and molecular characteristics of Cryptosporidium in dairy cattle in four Nile River delta provinces in Egypt. Modified Ziehl-Neelsen acid-fast microscopy was used to screen for Cryptosporidium oocysts in 1974 fecal specimens from animals of different ages on 12 farms. Positive fecal specimens were identified from all studied farms with an overall prevalence of 13.6%. By age group, the infection rates were 12.5% in pre-weaned calves, 10.4% in post-weaned calves, 22.1% in heifers, and 10.7% in adults. PCR-RFLP and DNA sequence analyses of microscopy-positive fecal specimens revealed the presence of four major Cryptosporidium species. In pre-weaned calves, C. parvum was most common (30/69 or 43.5%), but Cryptosporidium ryanae (13/69 or 18.8%), Cryptosporidium bovis (7/69 or 10.2%), and Cryptosporidium andersoni (7/69 or 10.2%) were also present at much higher frequencies seen in most industrialized nations. Mixed infections were seen in 12/69 (17.4%) of genotyped specimens. In contrast, C. andersoni was the dominant species (193/195 or 99.0%) in post-weaned calves and older animals. Subtyping of C. parvum based on sequence analysis of the 60kDa glycoprotein gene showed the presence of subtypes IIdA20G1 in nine specimens, IIaA15G1R1 in 27 specimens, and a rare subtype IIaA14G1R1r1b in one specimen. The common occurrence of non-C. parvum species and IId subtypes in pre-weaned calves is a distinct feature of cryptosporidiosis transmission in dairy cattle in Egypt. The finding of the same two dominant IIa and IId C. parvum subtypes recently found in humans in Egypt suggests calves can be potential reservoirs of zoonotic cryptosporidiosis.
在工业化国家，对奶牛中隐孢子虫属的分子特征进行了研究，结果表明，大多数隐孢子虫属为小隐孢子虫，尤其是未断奶小牛的 IIa 亚型。然而，在发展中国家，对不同年龄组奶牛中隐孢子虫种和小隐孢子虫亚型的分布情况，进行的研究较少。本研究对埃及尼罗河三角洲四个省份的奶牛中隐孢子虫的流行情况和分子特征进行了检测。用改良的齐尔-尼尔森酸性抗酸染色法对来自 12 个农场不同年龄的 1974 份粪便标本进行隐孢子虫卵囊筛查。从所有研究农场的阳性粪便标本中鉴定出，总体流行率为 13.6%。按年龄组划分，未断奶小牛的感染率为 12.5%，断奶后小牛为 10.4%，青年牛为 22.1%，成年牛为 10.7%。显微镜阳性粪便标本的 PCR-RFLP 和 DNA 序列分析显示，存在四种主要的隐孢子虫种。在未断奶小牛中，小隐孢子虫最为常见（30/69 或 43.5%），但也存在隐孢子虫丽亚种（13/69 或 18.8%）、牛隐孢子虫（7/69 或 10.2%）和安氏隐孢子虫（7/69 或 10.2%），这些种在大多数工业化国家的出现频率更高。12/69（17.4%）份基因分型标本存在混合感染。相比之下，安氏隐孢子虫是断奶后小牛和大龄动物中的主要种（193/195 或 99.0%）。基于 60kDa 糖蛋白基因序列分析的小隐孢子虫亚分型显示，9 份标本为 IIdA20G1 亚型，27 份标本为 IIaA15G1R1 亚型，1 份标本为罕见的 IIaA14G1R1r1b 亚型。未断奶小牛中非小隐孢子虫种和 IId 亚型的常见存在，是埃及奶牛隐孢子虫病传播的一个显著特征。在埃及最近发现人类中存在相同的两种主要的 IIa 和 IId 小隐孢子虫亚型，这表明小牛可能是人畜共患隐孢子虫病的潜在储主。
