A 24-year-old Shawano County Quarter Horse mare sampled on March 7 tested positive via polymerase chain reaction (PCR) testing for equine influenza virus. She was also positive for Streptococcus equi subspecies zooepidemicus. Five to seven horses are affected with clinical signs of respiratory disease at the boarding stable, where approximately 40 horses reside. Affected horses were isolated and the farm placed under a voluntary quarantine. The WDA reported that some horses at the stable had traveled to shows and competitions, and the vaccination status of the infected animals was unknown.

In Grant County approximately 30 horses at a private farm showed respiratory clinical signs, including coughing and nasal discharge. The WDA reported some were dyspneic—experiencing difficult or labored breathing—with low-grade fevers, and affected horses generally did not go off their feed. Horses had no recent history of travel, and there had been no recent new additions or visiting horses on the farm. The attending veterinarian sampled two of the most severely affected horses—which were not vaccinated—on March 22, and both were confirmed as PCR positive for influenza A virus (H3N8). The farm enacted a voluntary quarantine and horses were improving.

Finally, in Sauk County, a 9-year-old Quarter Horse gelding sampled on March 27 tested positive on PCR for equine influenza (H3N8). He had had been sick for a day with a high fever, lethargy, intermittent cough, and nasal and ocular discharge. Four other equids on the premises did not show clinical signs. The horse’s vaccination status is unknown, but WDA officials reported vaccination was unlikely. The premises put a voluntary quarantine in place and the gelding recovered.

About Equine Influenza

Equine influenza is a highly contagious respiratory disease that infects horses, ponies, and other equids, such as donkeys, mules, and zebras. The virus that causes it is spread via saliva and respiratory secretions from infected horses. Horses are commonly exposed via horse-to-horse contact; aerosol transmission from coughing and sneezing; and contact with humans’ contaminated hands, shoes, or clothes or contaminated tack, buckets, or other equipment.

Clinical signs of equine influenza infection can include a high fever (up to 106°F); a dry, hacking cough; depression; weakness; anorexia; serous (watery) nasal discharge; and slightly enlarged lymph nodes. Consider monitoring your horse’s health at shows by taking his temperature daily, which can help you pick up on signs of infection early and take appropriate measures to reduce disease spread.

​Vaccination is an important and inexpensive way to protect your horse. US Equestrian requires proof that horses have had an equine influenza vaccination within the six months prior to attending organization-sanctioned competitions or events. Your veterinarian can help you determine what other vaccines your horse might benefit from.

In addition to vaccinating, following strict biosecurity protocols can help reduce your horse’s chance of infection and disease. Such measures include quarantining new equine arrivals at barns, disinfecting buckets and equipment, and preventing nose-to-nose contact between horses.