Association of Equine Herpesvirus 5 with Mild Respiratory Disease in a Survey of EHV1, -2, -4 and -5 in 407 Australian Horses.
Authors: El-Hage Charles, Mekuria Zelalem, Dynon Kemperly, Hartley Carol, McBride Kristin, Gilkerson James
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary: EHV5 Association with Mild Respiratory Disease in Australian Horses Whilst equine alphaherpesviruses (EHV1 and EHV4) are well-documented respiratory pathogens, the clinical relevance of gammaherpesvirus infections—particularly EHV5—remains poorly characterised. El-Hage and colleagues analysed nasal swabs from 407 Victorian horses using quantitative PCR to establish prevalence rates and disease associations across four equine herpesviruses, comparing 249 clinically normal horses against 120 displaying signs of mild respiratory disease. EHV5 emerged as significantly more prevalent in diseased animals (70.8%) than in clinically normal horses (55%), with infected horses showing nearly twice the odds of exhibiting respiratory clinical signs (OR 1.98, 95% CI 1.25–3.16); conversely, EHV1 and EHV4 showed minimal association with clinical disease, with only one infected horse among eight total shedders demonstrating respiratory signs. Notably, quantitative viral loads did not differ between diseased and non-diseased groups, suggesting that EHV5 detection alone—rather than shedding intensity—may represent a meaningful risk factor. Practitioners should recognise EHV5 as a potential contributor to mild respiratory disease presentations, though further investigation into the mechanisms of EHV5 pathogenesis and its interaction with other respiratory pathogens is warranted before implementing specific management or treatment protocols.
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Practical Takeaways
- •EHV5 should be considered a potential contributor to mild respiratory disease in horses; practitioners should be aware of its association with clinical signs
- •The absence of a dose-response relationship suggests EHV5 may be one of multiple factors in respiratory disease pathogenesis rather than a sole causative agent
- •Testing for EHV5 in horses with unexplained mild respiratory signs may help differentiate viral from other causes, though clinical significance remains to be fully determined
Key Findings
- •EHV5 was detected in 70.8% of horses with clinical respiratory disease compared to 55% of clinically normal horses, a statistically significant difference
- •EHV5-positive horses had twice the odds of demonstrating clinical signs of respiratory disease (OR 1.98, 95% CI 1.25-3.16) compared to EHV5-negative horses
- •EHV1 and EHV4 shedding showed minimal association with respiratory disease, with only 1 of 8 horses shedding these viruses showing clinical signs
- •No significant difference in viral load between diseased and non-diseased horses was detected for any EHV type