Lack of detectable equine herpesviruses 1 and 2 in paraffin-embedded specimens of equine sarcoidosis

Background: Equine sarcoidosis is a rare, multisystemic, noncaseating, granulomatous and lymphoplasmacytic disease of unknown etiology. A recent report described a horse with granulomatous skin disease displaying histologic, electron microscopic, and polymerase chain reaction (PCR) findings consistent with equine herpesvirus 2 (EHV-2). Objective: To investigate the presence of EHV-2 and equine herpesvirus 1 (EHV-1) in 8 horses with sarcoidosis. Animals: Eight horses with sarcoidosis, reported previously. Methods: Retrospective study. PCR assays of the tissues were performed to detect DNA associated with EHV-1 and EHV-2. For both herpesviruses the target was their respective glycoprotein B gene. Positive controls consisted of DNA from viral cultures of culturettes from naturally occurring respiratory infections of EHV-1 and EHV-2. Results: The PCR analyses for both equine herpesviruses' DNA were negative in all 8 horses. Conclusion: The failure to detect DNA from EHV-1 and EHV-2 in paraffin-embedded skin of these 8 horses does not discount EHV-1 or EHV-2 as causing some cases of ES, but lends support to the presumably multifactorial etiologic nature of the disease.