Surveillance of equine influenza virus and cause specific morbidity rate in young horses in Ontario

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Diaz Méndez, Andrés
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University of Guelph

Nasopharyngeal swabs and acute and convalescent serum samples were collected from a total of 115 client-owned horses in twenty-three outbreaks of respiratory disease reported in Ontario (October 2003 to October 2005). Sera were paired and tested for antibody to equine influenza virus subtype 1 (AE1H7N7), equine influenza virus subtype 2 (AE2-H3N8), equine herpesvirus 1 (EHV1), equine herpesvirus 4 (EHV4), equine rhinovirus 1 (ERV1) and equine rhinovirus 2 (ERV2). Overall the cause specific morbidity rate of equine influenza virus in the respiratory outbreaks was 56.5% [determined by the single radial haemolysis test (SRH)]. The AE2-H3N8 was isolated from 15 horses in 5 outbreaks. Interestingly, four fold increase in antibody levels or presence of a high titre against ERV1 was observed in 11/23 outbreaks and ERV2 was observed in 2/4 outbreaks where AE2-H3N8 was diagnosed as the primary cause of disease using the SRH. In conclusion, AE2-H3N8 was found to be an important cause of equine respiratory disease. ERV1 and ERV2, which were present in 18/23 outbreaks, may represent an important component in equine respiratory disease in performance horses.

nasopharyngeal swabs, acute, convalescent, serum samples, horses, outbreak, respiratory diseas, Ontario, antibody, equine influenza virus subtype 1, equine influenza virus subtype 2, equine herpesvirus 1, equine herpesvirus 4, equine rhinovirus 1, equine rhinovirus 2