Detection of equine influenza virus gene in the air around infected horses.

Equine influenza virus (EIV) can be transmitted by inhalation of aerosolized droplets, direct contact, and contaminated fomites. However, to our knowledge, there are no reports of the recovery of EIV from the air surrounding infected horses. Here, we evaluated whether EIV can be recovered from the air in the stalls of experimentally infected horses by using an air sampler. Furthermore, we examined whether rapid molecular test kits with reaction times of less than 30 min can detect EIV from air samples for potential field application. Two horses kept in individual stalls were experimentally infected with EIV. Air samples were collected daily by using an air sampler until 13 days post-inoculation (dpi). Viral genes were detected in 26 out of 28 air samples from both horses at 1-13 dpi by real-time RT-PCR. A rapid molecular test kit based on real-time RT-PCR detected viral genes in 23 air samples from one horse at 1-9 and 12 dpi, and from the other at 1-13 dpi. These findings confirm that horses infected with EIV shed the virus into the air. Air sampling is safe for humans and horses and avoids the potential for injury when nasopharyngeal swabs need to be collected from untrained or aggressive horses. EIV RNA was detected in the air samples by using real-time RT-PCR or the rapid molecular test kit before the horses showed clinical signs. Thus, air samplers can detect EIV RNA as early as possible through routine testing in locations such as quarantine facilities.