Table 1_Influenza A virus shedding and reinfection during the post-weaning period in swine: longitudinal study of two nurseries.xlsx

IntroductionInfluenza A virus in swine (IAV-S) is common in the United States commercial swine population and has the potential for zoonotic transmission.ObjectiveTo elucidate influenza shedding the domestic pig population, we evaluated two commercial swine farms in Illinois, United States, for 7 weeks. Farm 1 had a recent IAV-S outbreak. Farm 2 has had IAV-S circulating for several years.MethodsForty post-weaning pigs on Farm 1 and 51 pigs from Farm 2 were individually monitored and sampled by nasal swabs for 7 weeks.ResultsRT-PCR results over time showed most piglets shed in the first 2 weeks post weaning, with 91.2% shedding in week one, and 36.3% in week two. No difference in the number of pigs shedding was found between the two nurseries. Reinfection events did differ between the farms, with 30% of piglets on Farm 1 becoming reinfected, compared to 7.8% on Farm 2. In addition, whole genome sequencing of nasal swab samples from each farm showed identical viruses circulating between the initial infection and the reinfection periods. Sequencing also allowed for nucleic and amino acid mutation analysis in the circulating viruses, as well the identification of a potential reverse zoonosis event. We saw antigenic site mutations arising in some pigs and MxA resistance genes in almost all samples.ConclusionThis study provided information on IAV-S circulation in nurseries to aid producers and veterinarians to screen appropriately for IAV-S, determine the duration of IAV-S shedding, and predict the occurrence of reinfection in the nursery period.

引言：猪流感A病毒（IAV-S）在美国的商业猪群中普遍存在，并具有潜在的动物源性传播风险。研究目的：为阐明家猪群中的流感排泄现象，本研究对美国伊利诺伊州的两家商业猪场进行了为期7周的评估。农场1近期发生了IAV-S疫情，而农场2则已持续数年存在IAV-S的循环。研究方法：对农场1的40头断奶后猪和农场2的51头猪进行个体监测和采样，采样方式为鼻腔拭子，持续7周。研究结果：随时间推移的RT-PCR检测结果表明，大部分猪崽在断奶后前两周开始排泄，其中第一周有91.2%的猪崽开始排泄，第二周为36.3%。两个猪舍中排泄猪的数量没有发现差异。农场间再感染事件存在差异，农场1的30%猪崽发生了再感染，而农场2为7.8%。此外，对每个农场鼻腔拭子样本的全基因组测序显示，初始感染期和再感染期之间循环的病毒是相同的。测序还允许对循环病毒进行核酸和氨基酸突变分析，以及识别潜在的逆向动物源性传播事件。我们观察到一些猪出现了抗原位点突变，几乎所有样本中都有MxA耐药基因。研究结论：本研究为猪场中IAV-S的循环提供了信息，以帮助生产者和兽医进行适当的IAV-S筛查，确定IAV-S排泄的持续时间，并预测断奶期再感染的发生。