Abstract：
Swine influenza A virus (swIAV) is a major pathogen affecting pigs with a huge economic impact and potentially zoonotic. Epidemiological studies in endemically infected farms permitted to identify critical factors favoring on-farm persistence, among which maternally-derived antibodies (MDAs). Vaccination is commonly practiced in breeding herds and might be used for immunization of growing pigs at weaning. Althoughinterference between MDAs and vaccination was reported in young piglets, its impact on swIAV transmission was not yet quantified. To this aim, this study reports on a transmission experiment in piglets with or without MDAs, vaccinated with a single dose injection at four weeks of age, and challenged 17 days post-vaccination. To transpose small-scale experiments to real-life situation, estimated parameters were used in a simulation tool to assess their influence at the herd level. Based on a thorough follow-up of the infection chain during the experiment, the transmission of the swIAV challenge strain was highly dependent on the MDA status of the pigs when vaccinated. MDA-positive vaccinated animals showed a direct transmission rate 3.6-fold higher than the one obtained in vaccinated animals without MDAs, estimated to 1.2. Vaccination nevertheless reduced significantly the contribution of airborne transmission when compared with previous estimates obtained in unvaccinated animals. The integration of parameter estimates in a large-scale simulation model, representing a typical farrow-to-finish pig herd, evidenced an extended persistence of viral spread when vaccination of sows and single dose vaccination of piglets was hypothesized. When extinction was quasi-systematic at year 5 post-introduction in the absence of sow vaccination but with single dose early vaccination of piglets, the extinction probability fell down to 33% when batch-to-batch vaccination was implemented both in breeding herd and weaned piglets. These results shed light on a potential adverse effect of single dose vaccination in MDA-positive piglets, which might lead to longer persistence of the SwIAV at the herd level.
摘要：
猪甲型流感病毒（swIAV）是影响猪的主要病原体，具有巨大的经济影响和潜在的人畜共患。在地方性感染的农场中进行流行病学研究，以确定有利于农场持久性的关键因素，其中母源抗体（MDAs）。疫苗接种通常在种畜中进行，可用于断奶时生长猪的免疫接种。尽管据报道，在幼猪中，MDA和疫苗接种之间存在干扰，其对swIAV传播的影响尚未量化.为了这个目标,这项研究报告了在有或没有MDAs的仔猪中进行的传播实验，在四周大时注射单剂量疫苗，并在接种疫苗后17天受到挑战。为了将小规模实验转移到现实生活中，在模拟工具中使用估计的参数来评估它们在畜群水平上的影响。根据实验过程中对感染链的全面随访，当接种疫苗时,swIAV攻击株的传播高度依赖于猪的MDA状态。MDA阳性接种疫苗的动物的直接传播率比没有MDA的接种疫苗的动物高3.6倍。估计为1.2。然而，与先前在未接种疫苗的动物中获得的估计相比，接种疫苗显着降低了空气传播的贡献。在大规模仿真模型中集成参数估计，代表典型的从牛群到鱼群，当假设母猪接种疫苗和仔猪单剂量接种疫苗时，病毒传播的持续时间延长。当在没有母猪疫苗接种但对仔猪进行单剂量早期疫苗接种的情况下，在引入后5年灭绝是准系统的，当在种猪群和断奶仔猪中实施逐批疫苗接种时，灭绝概率下降到33%。这些结果揭示了单剂量疫苗接种对MDA阳性仔猪的潜在不利影响。这可能会导致SwIAV在群体水平上的持续时间更长。
