Influenza A viruses (IAVs) infect humans and a variety of other animal species. Infections with some subtypes of IAV were also reported in domestic cats and dogs. In addition to animal health implications, close contact between companion animals and humans also poses a potential risk of zoonotic IAV infections. In this study, serum samples from different cat and dog cohorts were analyzed for IAV antibodies against seven IAV subtypes, using three distinctive IAV-specific assays differing in IAV subtype-specific discriminatory power and sensitivity. Enzyme-linked immunosorbent assays against the complete hemagglutinin (HA) ectodomain or the HA1 domain were used, as well as a novel nanoparticle-based, virus-free hemagglutination inhibition assay. Using these three assays, we found cat and dog sera from different cohorts to be positive for antibodies against one or more IAV subtypes and/or strains. Cat and dog serum samples collected after the 2009 pandemic H1N1 outbreak exhibit much higher seropositivity against H1 compared to samples from before 2009. Cat sera, furthermore, displayed higher reactivity for avian IAVs than dog sera. Our findings show the added value of using complementary serological assays, which are based on reactivity with different numbers of HA epitopes, to study IAV antibody responses and for improved serosurveillance of IAV infections. We conclude that infection of cats and dogs with both human and avian IAVs of different subtypes is prevalent. These observations highlight the role of cats and dogs in IAV ecology and indicate the potential of these companion animals to give rise to novel (reassorted) viruses with increased zoonotic potential.

中文翻译：

---

在猫和狗中对A型流感病毒抗体进行血清学筛查表明，经常感染不同的亚型。

甲型流感病毒（IAV）感染人类和其他各种动物。还报道了家猫和狗中有一些亚型的IAV感染。除了对动物健康的影响外，伴侣动物与人类之间的密切接触也构成人畜共患IAV感染的潜在风险。在这项研究中，使用三种不同的IAV亚型特异性区分能力和敏感性不同的独特的IAV特异性测定，分析了来自不同猫和狗队列的血清样品中针对7种IAV亚型的IAV抗体。使用针对完整血凝素（HA）胞外域或HA1域的酶联免疫吸附测定，以及新型的基于纳米颗粒的无病毒血凝抑制测定。使用这三种方法，我们发现来自不同队列的猫和狗血清对一种或多种IAV亚型和/或菌株的抗体呈阳性。与2009年之前的样本相比，2009年H1N1大流行爆发后收集的猫和狗血清样本显示出更高的抗H1血清阳性。此外，猫血清对禽IAV的反应性比狗血清高。我们的发现表明，使用互补血清学分析（基于与不同数量的HA表位的反应性）来研究IAV抗体反应并改善IAV感染的血清学监测，具有附加价值。我们得出结论，不同亚型的人和禽IAV感染猫和狗是普遍的。