Surveillance programme for important equine infectious respiratory pathogens in the USA.
Authors: Pusterla N, Kass P H, Mapes S, Johnson C, Barnett D C, Vaala W, Gutierrez C, McDaniel R, Whitehead B, Manning J
Journal: The Veterinary record
Summary
# Surveillance of Equine Respiratory Pathogens in the USA Between 2009 and 2011, a nationwide surveillance programme collected blood and nasal swabs from 761 equine cases presenting with acute upper respiratory signs or febrile neurological disease, using real-time PCR to identify equine influenza virus (EIV), equine herpesvirus types 1 and 4 (EHV-1 and EHV-4), and *Streptococcus equi* subspecies *equi*. Of the index cases, 26.4% tested positive for at least one pathogen, with EHV-4 predominating (82 cases), followed by EIV (60), *S. equi* (49) and EHV-1 (23), whilst 15 horses had dual infections and one had triple infection. Detection rates for each pathogen showed marked variation according to season, age, breed, sex and use category, indicating that risk stratification should inform both clinical investigation and biosecurity planning. These findings provide crucial epidemiological context for respiratory disease in North American equine populations and suggest that diagnostic protocols and vaccination strategies should be tailored based on local circulation patterns and individual animal risk factors rather than applied uniformly across all presentations.
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Practical Takeaways
- •EHV-4 is the most commonly detected respiratory pathogen in clinical cases across the USA, followed by EIV, making these priorities for diagnostic testing and vaccination protocols
- •Multiple pathogen infections occur in approximately 2% of cases (16/761), so consider testing for multiple agents rather than single pathogen panels when respiratory disease is suspected
- •Seasonal, age, and use-related patterns in pathogen prevalence should guide your risk assessment and biosecurity protocols for different horse populations and times of year
Key Findings
- •26.4% (201/761) of enrolled horses tested PCR-positive for one or more of the four pathogens studied
- •EHV-4 had the highest detection rate at 82 cases, followed by EIV (60 cases), S. equi subspecies equi (49 cases), and EHV-1 (23 cases)
- •Multiple infections occurred in 16 horses, including 15 double infections and 1 triple infection
- •Detection rates for all pathogens varied significantly by season, age, breed, sex, and use of the animal