Page 3 - Equine influenza e-Book
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Legal: Summary


        USA


       •  Reportable disease:
          o  Arizona.
          o  Louisiana.
          o  Mississippi.
          o  Vermont (type A).
          o  Virginia.
          o  Washington.
       •  OIE List B disease.

        UK


       •  No legislation, but Jockey Club regulations require primary and booster vaccinations of all horses
           entering racecourses.


        Age predisposition


       •  Foals: pneumonia.
       •  Adults: tracheobronchitis.

        Cost considerations


       •  Outbreaks in racing stables, breeding establishments and show barns. Marked impact on the equine
           industry.


        Pathogenesis



        Etiology


       •  Equine influenza A virus Equine influenza virus - an orthomyxovirus.
       •  Two main strains: H7N7 (formerly subtype 1) and H3N8 (formerly subtype 2).
       •  There have been very few reports of H7N7 subtype virus infections in the last 20 years, H3N8 infections
           predominate.
       •  There are two main lineages of H3N8 viruses: American and Eurasian.
       •  Host-species specific: infects horses, donkeys and mules only.

        Predisposing factors



        General


       •  Contact with infected equids.
       •  Stress, eg transport.
       •  Compromised local immunity, eg young foals.






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