Equine Influenza Virus (EIV) Outbreak on Hawaii Island

Alert to veterinarians statewide regarding an ongoing Equine Influenza Virus (H3N8) outbreak observed on the Big Island of Hawaii. The disease appears to be limited to Hawaii Island at this time. The HDOA Animal Disease Control Branch is monitoring the situation and if you have diagnosed EIV in a horse, please contact the deputy state veterinarian in your county to assist us with tracking the disease event.

Hawaii County: Dr. Kim Kozuma (808) 974-6503 or (808) 365-4346
Maui County: Dr. Rick Willer (808) 873-3559
Kauai and Honolulu Counties: Dr. Travis Heskett (808) 483-7131

Quick Facts about Equine Influenza

Etiologic agent: Influenza type A, H3N8.
Species affected: Currently, only horses. The literature suggests that dogs and cats can become infected.
• via droplets and aerosols formed by coughing and sneezing
• direct or indirect contact with nasal discharge
• shedding of the virus often precedes clinical signs
• short incubation period, usually one to three days
• virus is typically excreted only 7-10 days after infection
Clinical signs: Acute respiratory disease, beginning with high fever (up to 106°), coughing, nasal discharge, and occasionally mild swelling of submandibular lymph nodes. Secondary bacterial infections may develop. Healthy adult horses will typically recover within one to three weeks,
although there may be a persistent cough.
Diagnosis: Can be presumed based on history, clinical presentation, and ruling out other causes of fever
• HDOA’s Veterinary Laboratory does not perform diagnostic testing for Equine Influenza.
• A number of mainland veterinary diagnostic laboratories can test for Equine Influenza and other infectious etiologies which can cause similar clinical signs. Contact the mainland laboratory of your preference for specific guidance regarding sample collection, preservation, and submission.
What has been observed in this event:
• Infection has been self-limiting, lasting approximately two to three weeks.
• Vaccinated horses were less likely to develop clinical signs than unvaccinated horses.
• Clusters of ill horses have been observed associated with equine events.
• Practicing good biosecurity reduces the likelihood of spread.

For more information, visit the website of the Hawaii Dept. of Agriculture, Animal Disease Control Branch at http://hdoa.hawaii.gov/ai/main/eiv/ or contact the Animal Industry Division at (808) 483-7106.

Thanks to Jenee Odani, DVM, DACVP and Dr. Travis Heskett, DVM, DACVP who contributed technical information for this article. [3/7/18]