A Brief Introduction to Equine Influenza and Equine Influenza Viruses

  • Thomas M. ChambersEmail author
Part of the Methods in Molecular Biology book series (MIMB, volume 2123)


Equine influenza virus (EIV) is a common respiratory pathogen of horses and other equids in most parts of the world. EIV are Type A influenza viruses and two subtypes are known: H3N8 and H7N7. Both are believed to have evolved from avian influenza virus ancestors. The H3N8 subtype circulates widely, but the H7N7 subtype is thought to be extinct. The clinical disease in horses, caused by either subtype, is an upper respiratory infection of varying severity depending upon the immune status of the individual animal. It is not normally life-threatening in itself except in very young foals; however it predisposes infected equids to secondary infections capable of producing life-threatening pneumonias. Vaccines are available and widely used in some horse populations, but their effectiveness is limited by antigenic drift and other factors, and vaccinated animals with subclinical infections have been responsible for introduction of EIV into susceptible populations. EIV has spread into canines.

Key words

Equine influenza virus Type A influenza Pathogenesis Vaccine Antigenic drift 


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Copyright information

© This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply. 2020

Authors and Affiliations

  1. 1.Department of Veterinary Science, Maxwell H. Gluck Equine Research CenterUniversity of KentuckyLexingtonUSA

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