Veterinary Population Medicine Department, College of Veterinary Medicine, University of Minnesota, St. Paul, MN, USA.
Departamento de Ciencias Veterinarias y Salud Pública, Facultad de Recursos Naturales, Universidad Católica de Temuco, Temuco, Chile.
Prev Vet Med. 2021 Mar;188:105257. doi: 10.1016/j.prevetmed.2021.105257. Epub 2021 Jan 5.
Piglets prior to weaning play a central role in maintaining influenza infections in breeding herds and the use of nurse sows is a common practice to adopt piglets that fall behind and that otherwise would die. Transmission of influenza A virus (IAV) from nurse sows to adopted pigs has been reported experimentally, however, the importance of this route of transmission under field conditions has not yet been elucidated. A cohort study to assess the IAV status in nurse and control sows and their respective litters was carried out in three influenza positive breed-to-wean farms. A total of 94 control and 90 nurse sows were sampled by collecting udder skin wipes and oral swabs at enrollment (∼ 5-7 days after farrowing) and at weaning. Six piglets per litter were sampled randomly at enrollment, 2 days post-enrollment (DPE), 4 DPE, at day 14 of lactation (14DL) and at weaning. At enrollment, 76 % (69/91) of udder wipes and 3 % (3/89) of oral swabs from nurse sows were positive by rRT-PCR compared with 23 % (21/92) of udder wipes and 0 % (0/85) of oral swabs from control sows. Of the 94 control litters sampled, 11.7 %, 14.9 %, 22.9 %, 46.8 % and 63.9 % tested rRT-PCR IAV positive at enrollment, 2DPE, 4DPE, 14 DL and weaning, respectively. Corresponding prevalence for nurse sow litters were 12.2 %, 30.2 %, 37.0 %, 59.4 % and 56.4 %. The odds of IAV positivity were significantly higher (p < 0.05) for litters from nurse sows 2 DPE (odd ratio (OR) = 6.13, 95 % CI = 1.8-21.2), 4 DPE (OR = 5.5, 95 % CI = 1.7-17.8) and 14 DL (OR = 3.7, 95 % CI = 1.1-12.3). However, there were no differences in the proportion of positive samples at weaning. Moreover, approximately 18 % of the control sows and 11 % of nurse sows that tested IAV negative in oral swabs at enrollment, tested IAV positive at weaning. This study indicates that nurse sows can contribute to the transmission and perpetuation of IAV infections in pigs prior to weaning, particularly during the first week after adoption.
在断奶前的仔猪在繁殖群中维持流感感染方面发挥着核心作用，而使用奶妈母猪来收养掉队的仔猪并使其存活是一种常见做法。已报道实验中从奶妈母猪向收养仔猪传播甲型流感病毒（IAV），但在田间条件下这种传播途径的重要性尚未阐明。本研究在三个流感阳性的从配种到断奶的农场中开展了一项评估奶妈和对照母猪及其各自仔猪的 IAV 状态的队列研究。在入组时（大约在产仔后 5-7 天）和断奶时，共采集了 94 头对照母猪和 90 头奶妈母猪的乳头拭子和口腔拭子样本。在入组时，每个窝随机采集 6 头仔猪样本，在入组后 2 天（2DPE）、4DPE、哺乳期第 14 天（14DL）和断奶时采集样本。与 23%（21/92）的对照母猪的乳头拭子和 0%（0/85）的口腔拭子相比，76%（69/91）的奶妈母猪的乳头拭子和 3%（3/89）的口腔拭子通过 rRT-PCR 检测呈阳性。在入组时，94 个对照窝中分别有 11.7%、14.9%、22.9%、46.8%和 63.9%的窝通过 rRT-PCR 检测 IAV 呈阳性，而在 2DPE、4DPE、14DL 和断奶时的相应流行率分别为 12.2%、30.2%、37.0%、59.4%和 56.4%。奶妈母猪窝的 IAV 阳性率明显更高（p<0.05），在 2DPE（比值比（OR）=6.13，95%CI=1.8-21.2）、4DPE（OR=5.5，95%CI=1.7-17.8）和 14DL（OR=3.7，95%CI=1.1-12.3）时。然而，在断奶时的阳性样本比例上没有差异。此外，在入组时，约 18%的对照母猪和 11%的奶妈母猪的口腔拭子 IAV 检测阴性，但在断奶时的检测呈阳性。本研究表明，奶妈母猪可在断奶前，特别是在收养后的第一周内，促进 IAV 感染在仔猪中的传播和持续存在。
