Allerson M W, Davies P R, Gramer M R, Torremorell M
Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN, USA.
Transbound Emerg Dis. 2014 Dec;61(6):490-9. doi: 10.1111/tbed.12053. Epub 2013 Jan 8.
Influenza A viruses are common causes of respiratory disease in pigs and can be transmitted among multiple host species, including humans. The current lack of published information on infection dynamics of influenza viruses within swine herds hinders the ability to make informed animal health, biosecurity and surveillance programme decisions. The objectives of this serial cross-sectional study were to describe the infection dynamics of influenza virus in a two-site swine system by estimating the prevalence of influenza virus in animal subpopulations at the swine breeding herd and describing the temporal pattern of infection in a selected cohort of growing pigs weaned from the breeding herd. Nasal swab and blood samples were collected at approximately 30-day intervals from the swine breeding herd (Site 1) known to be infected with pandemic 2009 H1N1 influenza virus. Sows, gilts and neonatal pigs were sampled at each sampling event, and samples were tested for influenza virus genome using matrix gene RRT-PCR. Influenza virus was detected in neonatal pigs, but was not detected in sow or gilt populations via RRT-PCR. A virus genetically similar to that detected in the neonatal pig population at Site 1 was also detected at the wean-to-finish site (Site 2), presumably following transportation of infected weaned pigs. Longitudinal sampling of nasal swabs and oral fluids revealed that influenza virus persisted in the growing pigs at Site 2 for at least 69 days. The occurrence of influenza virus in neonatal pigs, but not breeding females, at Site 1 emphasizes the potential for virus maintenance in this dynamic subpopulation, the importance of including this subpopulation in surveillance programmes and the potential transport of influenza virus between sites via the movement of weaned pigs.
甲型流感病毒是猪呼吸道疾病的常见病因，可在包括人类在内的多种宿主物种之间传播。目前缺乏关于猪群中流感病毒感染动态的已发表信息，这阻碍了做出明智的动物健康、生物安全和监测计划决策的能力。这项系列横断面研究的目的是通过估计种猪场动物亚群中流感病毒的流行率，并描述从种猪场断奶的选定生长猪群中的感染时间模式，来描述双地点养猪系统中流感病毒的感染动态。从已知感染2009年大流行性H1N1流感病毒的种猪场（地点1）每隔约30天采集鼻拭子和血液样本。每次采样时对母猪、后备母猪和新生仔猪进行采样，并使用基质基因逆转录-聚合酶链反应（RRT-PCR）检测样本中的流感病毒基因组。在新生仔猪中检测到流感病毒，但通过RRT-PCR在母猪或后备母猪群体中未检测到。在育肥场（地点2）也检测到一种与在地点1的新生仔猪群体中检测到的病毒基因相似的病毒，推测是在感染的断奶仔猪运输之后。对鼻拭子和口腔液体的纵向采样显示，地点2的生长猪中流感病毒持续存在至少69天。地点1新生仔猪而非繁殖母猪中出现流感病毒，强调了在这个动态亚群中病毒维持的可能性、将这个亚群纳入监测计划的重要性以及流感病毒通过断奶仔猪的移动在不同地点之间传播的可能性。
