Detection of equid herpesviruses 2 and 5 in a herd of 266 Lipizzaners in association with ocular findings

A herd of Lipizzaners (n=266) in three locations [Federal stud Piber (Styria), Heldenberg (Lower Austria) and the Spanish Riding School Vienna (Vienna)] were examined for ocular diseases and tested for herpesviruses (HVs) in PBMCs, nasal- and conjunctival swabs. In 167 (62.8%) horses equid herpesvirus-2 (EHV-2) nucleic acid was identified in at least one of the investigated samples, and 136 (51.1%) horses were positive for equid herpesvirus-5 (EHV-5) nucleic acid in at least one of the samples. One hundred and five (39.5%) of the horses mentioned above were identified with EHV-2/EHV-5 double infections. The results were correlated with potential influence factors such as age, gender, location, and housing. Statistical analysis demonstrated a significantly higher percentage of horses diagnosed with HV infections stabled in one location (Piber); also, housing in free stalls was associated with a higher rate of HV infections. Horses carrying EHV-2 or EHV-5 nucleic acid were significantly younger than the negative group. Statistical analysis of PCR results and ophthalmic findings did not prove a significant association between any disease pattern and presence of the equid gammaherpesviruses EHV-2 and EHV-5. The results of this herd survey indicate that horses younger than eight years of age, housed in free stalls with high population densities have a significantly increased risk for infection with EHV-2 and EHV-5. However no prediction can be made whether this results in ophthalmic disease. This is the first ophthalmic-virologic survey of this magnitude in a single horse breed.