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.