Drug Peramivir Could Help Horses Suffering from Flu

Flu season for horses can be any season. And considering that even horses vaccinated against the equine influenza virus (EIV) can still “catch the flu,” this disease is cause for concern. A group of Japanese researchers, however, recently evaluated a flu inhibitor in horses and found that it could help EIV-infected animals recover more quickly.

“The flu, caused by EIV, is one of the most important respiratory diseases in horses,” said Takashi Yamanaka from the Epizootic Research Center at the Equine Research Institute, operated by the Japan Racing Association. EIV is highly contagious; causes fever, nasal discharge, depression, anorexia, and coughing; and can lead to fatal pneumonia. Affected horses require time off from training and performing to receive treatment and recover. What’s worse, influenza outbreaks occur even in vaccinated horses due to the fact that the vaccine is not 100% effective against all “field” strains of EIV.

Researchers have tested several EIV inhibitors in horses, but those tested required oral administration several times per day or needed to be inhaled. Neither approach is overly practical for horses and owners. But Yamanaka recently took a look at a human flu inhibitor for possible use in horses.

“Peramivir is a pharmaceutical drug that inhibits one of the key enzymes, neuraminidase (NA), on the influenza virus,” explained Yamanaka. "Peramivir (has been) licensed for use in humans since 2010.”

To determine whether a single intravenous injection of peramivir was effective for treating equine influenza, Yamanaka and colleagues tested the drug in laboratory viral cultures and in six horses experimentally infected with EIV, all of which had nasal discharge, a fever, and tested positive for the equine influenza virus using a commercially available kit. Key findings of the study were:

  • Peramivir inhibited the enzymatic activity of NA in seven different field strains of EIV in the laboratory;
  • Experimentally infected horses subsequently administered peramivir had milder clinical signs and recovered more quickly than horses that were administered only saline (control group); and
  • Treated horses shed the influenza virus for a shorter period of time than the control horses.

Yamanaka concluded, “These results clearly show that peramivir may be a very useful tool for treating EIV and may also be able to help limit the spread of this highly contagious virus in the horse population during outbreaks.”

Commenting on the study, Nicola Pusterla, DVM, PhD, Dipl. ACVIM, an associate professor of equine internal medicine and chief of large animal medicine and section head of equine medicine and dentistry at the University of California, Davis, School of Veterinary Medicine, said, “The drug is promising … (but) we don't have any safety or (pharmacokinetic) data [regarding how the horse’s body metabolizes the drug]. I am expecting the drug to be expensive, especially when you compare the body weight difference between a human being and a horse.”

That said, American horse owners will likely have to wait for access to this medication, as peramivir is currently only approved in Japan and Korea.

The study, “Efficacy of a single intravenous dose of the neuramidase inhibitor peramivir in the treatment of equine influenza,” was published in The Veterinary Journal.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.