Infectious Diseases

Earlier Detection of EIV

By Adam Marcus

A new study shows equine influenza virus (EIV) can be detected in the air around infected horses, even before the animals appear sick.

“I believe that regular air sampling and testing of air samples will enable early detection of infectious diseases” in horses, said Manabu Nemoto, DVM, PhD, of the Equine Research Institute at the Japan Racing Association, in Tochigi, who led the study. “This technology is not widely used in the Japanese equine industry, so I hope that air sampling will be useful as a new technology for infectious disease control in the future,” added Dr. Nemoto, who also is an expert at the World Organisation for Animal Health Reference Laboratory for Equine Influenza.

For the study, Dr. Nemoto and his colleagues infected 2 horses—housed in separate stalls—with EIV, then collected air samples for the next 13 days using the AerosolSense Sampler (Thermo Fisher Scientific). The machine can detect a range of animal and human viruses, including influenza, SARS-Cov-2, the cause of COVID-19, and respiratory syncytial virus. The test also can be paired with polymerase chain reaction (PCR) testing to identify genetic material in samples.

According to Dr. Nemoto’s group, EIV RNA turned up in 26 of 28 aerosol samples between day 1 and day 13 of the study, demonstrating the infected horses shed detectable amounts of virus even when they did not exhibit clinical signs of infection.

The researchers also used a less sophisticated rapid test, which can return a result in 30 minutes through real-time PCR, to look for EIV. Again, the virus was readily apparent, showing up in 23 of 28 tests across the study period.

“These findings confirm that horses infected with EIV shed the virus into the air,” the researchers reported. “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.”

Dr. Nemoto acknowledged the presence of viral DNA in an air sample does not necessarily mean an animal is sick. “It depends on the stages of infection. Viruses detected in the early stages of infection are linked to clinical signs, whereas viruses in the late stages of infection are not,” he said. “The air sampler can detect inactivated viruses that are not associated with clinical signs, especially in the late stages of infection.”

Dr. Nemoto said the air sampler also can detect viral genes from environmental surfaces in the stalls, rather from aerosols shed directly by the horses. “This means that, for accurate evaluation, environmental surfaces in the stalls must be cleaned and disinfected before using the air sampler,” he said. MeV

For more information:
Nemoto M, Kawanishi N, Kambayashi Y. Detection of equine influenza virus gene in the air around infected horses. Vet Microbiol. 2025;302:110388 https://www.sciencedirect.com/science/article/abs/pii/S0378113525000239