Epizootic Research Center, Equine Research Institute, the Japan Racing Association, 1400-4 Shiba, Shimotsuke, Tochigi, 329-0412, Japan.
Acta Vet Scand. 2012 Apr 16;54(1):25. doi: 10.1186/1751-0147-54-25.
Since equine influenza A virus (H3N8) was transmitted to dogs in the United States in 2004, the causative virus, which is called canine influenza A virus (CIV), has become widespread in dogs. To date, it has remained unclear whether or not CIV-infected dogs could transmit CIV to horses. To address this, we tested whether or not close contact between horses and dogs experimentally infected with CIV would result in its interspecies transmission.
Three pairs of animals consisting of a dog inoculated with CIV (10(8.3) egg infectious dose 50/dog) and a healthy horse were kept together in individual stalls for 15 consecutive days. During the study, all the dogs and horses were clinically observed. Virus titres in nasal swab extracts and serological responses were also evaluated. In addition, all the animals were subjected to a gross pathological examination after euthanasia.
All three dogs inoculated with CIV exhibited clinical signs including, pyrexia, cough, nasal discharge, virus shedding and seroconversion. Gross pathology revealed lung consolidations in all the dogs, and Streptococcus equi subsp. zooepidemicus was isolated from the lesions. Meanwhile, none of the paired horses showed any clinical signs, virus shedding or seroconversion. Moreover, gross pathology revealed no lesions in the respiratory tracts including the lungs of the horses.
These findings may indicate that a single dog infected with CIV is not sufficient to constitute a source of CIV infection in horses.
自 2004 年美国的马流感 A 病毒（H3N8）传播给犬以来，这种被称为犬流感 A 病毒（CIV）的致病病毒已在犬中广泛传播。迄今为止，仍不清楚 CIV 感染的犬是否会将 CIV 传播给马。为了解决这个问题，我们测试了 CIV 感染的犬和马之间的密切接触是否会导致其种间传播。
三对动物，包括接种 CIV（10（8.3）个鸡蛋感染剂量/只狗）的犬和一匹健康的马，被关在单独的畜栏中连续 15 天。在研究过程中，所有的犬和马都进行了临床观察。还评估了鼻拭子提取物中的病毒滴度和血清学反应。此外，所有动物在安乐死后都进行了大体病理检查。
所有接种 CIV 的三只犬均出现发热、咳嗽、鼻漏、病毒脱落和血清转化等临床症状。大体病理学显示所有犬的肺部均有实变，从病变中分离出马链球菌兽疫亚种。同时，配对的马均未出现任何临床症状、病毒脱落或血清转化。此外，马的呼吸道包括肺部均无肉眼可见的病变。
这些发现可能表明，一只感染 CIV 的犬不足以成为马感染 CIV 的来源。
