Veterinary Population Medicine Department, University of Minnesota, St. Paul, MN, United States of America.
Health Services, Pipestone Veterinary Services, Pipestone, MN, United States of America.
PLoS One. 2019 Jan 14;14(1):e0210700. doi: 10.1371/journal.pone.0210700. eCollection 2019.
Reducing the number of influenza A virus (IAV) infected pigs at weaning is critical to minimize IAV spread to other farms. Sow vaccination is a common measure to reduce influenza levels at weaning. However, the impact of maternally-derived antibodies on IAV infection dynamics in growing pigs is poorly understood. We evaluated the effect of maternally-derived antibodies at weaning on IAV prevalence at weaning, time of influenza infection, number of weeks that pigs tested IAV positive, and estimated quantity of IAV in nursery pigs. We evaluated 301 pigs within 10 cohorts for their influenza serological (seroprevalence estimated by hemagglutination inhibition (HI) test) and virological (prevalence) status. Nasal swabs were collected weekly and pigs were bled 3 times throughout the nursery period. There was significant variability in influenza seroprevalence, HI titers and influenza prevalence after weaning. Increase in influenza seroprevalence at weaning was associated with low influenza prevalence at weaning and delayed time to IAV infection throughout the nursery. Piglets with IAV HI titers of 40 or higher at weaning were also less likely to test IAV positive at weaning, took longer to become infected, tested IAV RT-PCR positive for fewer weeks, and had higher IAV RT-PCR cycle threshold values compared to piglets with HI titers less than 40. Our findings suggest that sow vaccination or infection status that results in high levels of IAV strain-specific maternally-derived antibodies may help to reduce IAV circulation in both suckling and nursery pigs.
减少断奶时感染甲型流感病毒 (IAV) 的猪的数量对于最大限度地减少 IAV 传播到其他农场至关重要。母猪接种疫苗是减少断奶时流感水平的常用措施。然而，母源抗体对生长猪中 IAV 感染动态的影响知之甚少。我们评估了断奶时母源抗体对断奶时 IAV 流行率、流感感染时间、猪 IAV 阳性检测周数以及保育猪中 IAV 估计数量的影响。我们评估了 10 个队列中的 301 头猪的流感血清学（通过血凝抑制 (HI) 试验估计的血清阳性率）和病毒学（流行率）状态。每周采集鼻拭子，整个保育期内猪被采血 3 次。流感血清阳性率、HI 滴度和断奶后流感流行率存在显著差异。断奶时流感血清阳性率增加与断奶时流感流行率低和整个保育期 IAV 感染时间延迟有关。断奶时 HI 滴度为 40 或更高的仔猪在断奶时也不太可能检测到 IAV 阳性，感染时间更长，RT-PCR 检测到 IAV 阳性的周数更少，并且与 HI 滴度低于 40 的仔猪相比，RT-PCR 循环阈值值更高。我们的研究结果表明，母猪接种疫苗或感染状态导致高水平的 IAV 特异性母源抗体可能有助于减少哺乳仔猪和保育仔猪中 IAV 的传播。
