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The remainder of the 2015 Far West Regional Morgan Championship Horse Show was cancelled due to illness late last week. Samples from three of the affected horses were tested at the Oregon State University Veterinary Diagnostic Lab on Monday, June 22 and were confirmed to be positive for Equine Influenza A Virus. The samples were negative for Equine Herpes Virus 1 & 4 and for Equine Viral Arteritis. The remainder of the samples will be tested via Merck's Equine Respiratory Pathogen Surveillance Program at UC Davis Veterinary Diagnostic Lab on Tuesday, but we expect the results will confirm OSU's diagnosis. 

All affected horses are recovering with only symptomatic treatment, though the number of cases has increased to approximately the mid 20s that we are aware of as of Monday.

The Equine Influenza Virus (EIV) can persist in the environment (on inanimate objects) for only about two to three days, fortunately, Infected horses should be quarantined for 21 days and any exposed but non symptomatic horses can be quarantined for 14 days. This virus is very contagious, and can travel up to 50 yards through the air, so quarantine arrangement should take this into account. Infected horses should be rested from work for one week for every day of fever they experience or there is risk of cardiac muscle damage.

Intranasal vaccines will provide the most rapid protection, usually by day five, against influenza. Intramuscular influenza vaccines are effective as well, but take longer (about two weeks) to provide protection. Make sure your vaccine carries the more recent strains (A2/Clade 1/North American). 

For more information for owners, go to http://www.aaep.org/custdocs/Influenza%20guidelines.pdf.
And for those who enjoy the technical details go to http://www.aaep.org/info/equine-influenza.