Clinical, serological and molecular investigations of EHV-1 and EHV-4 in 15 unweaned thoroughbred foals.
Authors: Marenzoni M L, Passamonti F, Cappelli K, Veronesi F, Capomaccio S, Supplizi A Verini, Valente C, Autorino G, Coletti M
Journal: The Veterinary record
Summary
# Editorial Summary: EHV-1 and EHV-4 in Unweaned Thoroughbred Foals Fifteen unweaned thoroughbred foals born to vaccinated mares were monitored over six months with repeated nasopharyngeal swabs and serological testing to establish whether equine herpesvirus types 1 and 4 were circulating on a stud farm and their role in respiratory disease. Despite stringent maternal vaccination protocols, both EHV-1 and EHV-4 were detected on the premises and confirmed in association with clinical respiratory signs in some foals, though viral circulation occurred regardless of clinical presentation. PCR proved effective at detecting viral presence in the nasopharyngeal tract but showed no significant difference in detection rates between clinically affected and unaffected foals, limiting its diagnostic specificity for predicting disease; serological assessment via seroneutralisation proved more informative for determining infection status. These findings underscore that vaccination alone cannot guarantee prevention of herpesavirus circulation in stud environments, and that clinicians should combine PCR results with clinical assessment and serological data rather than relying on molecular detection as a standalone diagnostic tool. The work highlights the value of integrated surveillance protocols on breeding premises and the need for comprehensive biosecurity measures alongside immunisation programmes.
Read the full abstract on PubMed
Practical Takeaways
- •Vaccination of mares does not guarantee prevention of EHV-1 and EHV-4 transmission to unweaned foals on the same premises
- •Respiratory clinical signs in young foals on stud farms should raise suspicion for herpesvirus infection even in vaccinated populations
- •PCR testing is better used for epidemiological confirmation of herd viral circulation rather than individual diagnostic purposes
Key Findings
- •EHV-1 and EHV-4 circulated on a thoroughbred stud farm despite stringent vaccination regimens in vaccinated mares
- •Both viruses were associated with respiratory disease in unweaned foals
- •PCR was effective for confirming viral circulation on premises but not particularly helpful as a diagnostic tool for individual cases
- •Foals showed three clinical patterns: asymptomatic non-seroconverted, symptomatic seroconverted, and symptomatic non-seroconverted