Avendaño Catalina, Ramo Ana, Vergara-Castiblanco Claudia, Sánchez-Acedo Caridad, Quílez Joaquín
Faculty of Animal Sciences, University of Applied and Environmental Sciences, U.D.C.A, Bogotá, Colombia.
Department of Animal Pathology, Faculty of Veterinary Sciences, University of Zaragoza, Miguel Servet 177, 50013, Zaragoza, Spain.
Parasitol Res. 2018 May;117(5):1317-1323. doi: 10.1007/s00436-018-5818-6. Epub 2018 Feb 26.
Fecal specimens from 432 pre-weaned calves younger than 35 days were collected over a 2-year period (2010-2012) from 74 dairy cattle farms in the central area of Colombia. These samples were microscopically examined for the presence of Cryptosporidium oocysts, and positive specimens were selected for molecular examination. Microscopy revealed that 115 calves (26.6%) from 44 farms (59.5%) tested positive. Oocyst shedding was recorded in calves aged 3-day-old onwards, although the infection rate peaked at 8-14 days (40.7%). Infection rates were higher in diarrheic (52.2%) than in non-diarrheic calves (19.9%) (p < 0.0001, χ), and infected calves had up to seven times more probability of having diarrhea than non-infected calves. Cryptosporidium species and subtypes were successfully identified in 73 samples from 32 farms. Restriction and sequence analyses of the SSU rRNA gene revealed C. parvum in all but two isolates identified as Cryptosporidium bovis. Sequence analyses of the 60-KDa glycoprotein (gp60) gene revealed eight subtypes within the IIa family. An unusual subtype (IIaA18G5R1) was the most prevalent and widely distributed (more than 66% specimens and 68% farms) while the subtype most frequently reported in cattle worldwide (IIaA15G2R1) was found in less than 13% of specimens and 16% farms. The remaining subtypes (IIaA16G2R1, IIaA17G4R1, IIaA20G5R1, IIaA19G6R1, IIaA20G6R1, and IIaA20G7R1) were restricted to 1-3 farms. This is the first large-sample size study of Cryptosporidium species and subtypes in Colombia and demonstrates the genetic uniqueness of this protozoan in cattle farms in this geographical area.
在2010年至2012年的两年时间里，从哥伦比亚中部地区的74个奶牛场收集了432头35日龄以下断奶前犊牛的粪便样本。对这些样本进行显微镜检查，以检测隐孢子虫卵囊的存在，并选择阳性样本进行分子检测。显微镜检查显示，来自44个农场（59.5%）的115头犊牛（26.6%）检测呈阳性。虽然感染率在8至14日龄时达到峰值（40.7%），但在3日龄及以上的犊牛中记录到了卵囊排出。腹泻犊牛的感染率（52.2%）高于非腹泻犊牛（19.9%）（p < 0.0001，χ），感染犊牛患腹泻的可能性是非感染犊牛的7倍。在来自32个农场的73个样本中成功鉴定出了隐孢子虫的种类和亚型。对小亚基核糖体RNA（SSU rRNA）基因的限制性分析和序列分析显示，除了两株鉴定为牛隐孢子虫的分离株外，其余均为微小隐孢子虫。对60 kDa糖蛋白（gp60）基因的序列分析揭示了IIa家族中的8个亚型。一种不寻常的亚型（IIaA18G5R1）最为普遍且分布广泛（超过66%的样本和68%的农场），而全球牛中最常报道的亚型（IIaA15G2R1）在不到13%的样本和16%的农场中被发现。其余亚型（IIaA16G2R1、IIaA17G4R1、IIaA20G5R1、IIaA19G6R1、IIaA20G6R1和IIaA20G7R1）仅限于1至3个农场。这是哥伦比亚首次对隐孢子虫种类和亚型进行的大样本量研究，证明了该原生动物在该地理区域奶牛场中的遗传独特性。
