Chandrasekhar Reddy Rachamreddy Venkata, Putla Bajibabu, Sarangi Laxmi Narayan, Rana Samir Kumar, Surendra Kota Sri Naga Leela, Ponnanna Nadikerianda Muthappa, Sharma Girish Kumar
National Dairy Development Board Research and Development Laboratory, IIL Campus, Gachibowli, Hyderabad, 500032, Telangana, India.
National Dairy Development Board, Anand, 388001, Gujarat, India.
Theriogenology. 2020 Nov;157:467-471. doi: 10.1016/j.theriogenology.2020.08.021. Epub 2020 Aug 19.
Infectious bovine rhinotracheitis (IBR) caused by bovine alphaherpesvirus 1 (BoHV-1) is an economically important disease of cattle and buffaloes. Following acute infection, the virus usually attains latency in the sensory neurons. Stress-induced reactivation of latency can cause the infected animals to intermittently shed the virus in body secretions including semen. A longitudinal analysis was carried out to study BoHV-1 shedding in the semen of IBR seropositive cattle and buffaloes. The study involved data generated from the screening of 119,850 extended frozen semen (EFS) batches, collected from 1,229 IBR seropositive bulls, over a period of four years (April 2015 to March 2019). A TaqMan based real-time PCR assay was employed to detect the gB gene BoHV-1 DNA in the EFS batch samples. Each sample was tested in duplicate and amplification in any of the replicates at or below the threshold cycle (Ct ≤ 40) was considered positive. The overall positivity of BoHV-1 in EFS batches was 1.18%. About 41% of the bulls (509 of 1,229) were found to have excreted the virus in semen at least once during the study period. The frequency of viral shedding in buffaloes (0.96%) was significantly lower than that of cattle (1.3%) (p < 0.001). No significant difference was noted in the rate of shedding between the first and the second ejaculates collected on the same day (p = 0.607). The rate of shedding also did not vary among various breeds of cattle (p = 0.454) or with the age of the bulls (p = 0.054). No significant variation in the shedding rate was observed in cattle across different seasons (p = 0.101); while in buffaloes, the rate was higher in autumn (1.2%) than in winter (0.7%) (p = 0.037). The difference in positivity among semen stations was statistically significant (p < 0.001). Analysis of data revealed that ≥100 EFS batch samples/bull were screened from 361 of the 1,229 bulls included in the study. None of the EFS batches screened from 39 of these 361 bulls were found positive during the four years, suggesting they were non-shedders. Further research is warranted to delineate the underlying features of the seropositive non-shedders; following which an adequate risk assessment may be made for the maintenance of infected but non-shedding bulls in semen production.
由牛α疱疹病毒1型（BoHV-1）引起的传染性牛鼻气管炎（IBR）是牛和水牛的一种具有重要经济影响的疾病。急性感染后，该病毒通常在感觉神经元中潜伏。应激诱导的潜伏激活可导致受感染动物在包括精液在内的身体分泌物中间歇性排毒。进行了一项纵向分析，以研究IBR血清阳性牛和水牛精液中的BoHV-1排毒情况。该研究涉及对1229头IBR血清阳性公牛在四年期间（2015年4月至2019年3月）采集的119,850批冷冻精液（EFS）进行筛查所产生的数据。采用基于TaqMan的实时PCR检测法检测EFS批次样本中的BoHV-1 gB基因DNA。每个样本进行重复检测，任何一个重复样本在阈值循环（Ct≤40）及以下出现扩增则被视为阳性。EFS批次中BoHV-1的总体阳性率为1.18%。在研究期间，约41%（1229头中的509头）的公牛被发现至少有一次精液排毒。水牛的病毒排毒频率（0.96%）显著低于牛（1.3%）（p<0.001）。同一天采集的第一次和第二次射精的排毒率无显著差异（p=0.607）。不同品种的牛之间的排毒率也没有差异（p=0.454），也与公牛的年龄无关（p=0.054）。不同季节牛的排毒率没有显著变化（p=0.101）；而在水牛中，秋季的排毒率（1.2%）高于冬季（0.7%）（p=0.037）。精液站之间的阳性率差异具有统计学意义（p<0.001）。数据分析显示，在纳入研究的1229头公牛中的361头中，每头公牛筛查了≥100批EFS样本。在这361头公牛中的39头所筛查的EFS批次在四年期间均未发现阳性，表明它们不排毒。有必要进一步研究以明确血清阳性不排毒者的潜在特征；在此之后，可对精液生产中感染但不排毒的公牛的饲养进行充分的风险评估。
