Here we describe OvHV-2 DNA in the blood and semen of asymptomatic boars and from the brain of symptomatic sows and gilts with MCF that was probably transmitted by artificial insemination.
OvHV-2 DNA was detected by using a specific PCR (4) in 5 of 7 paraffinized sections of the brainstem (5).
To find possible carriers of the virus, blood samples were collected from 9 pregnant sows, 10 nonpregnant sows, and 30 breeding boars and analyzed for OvHV-2 DNA.
Our findings of OvHV-2 DNA in the semen of asymptomatic boars suggest that the OvHV-2 in the sows and gilts originated from asymptomatic boars that were responsible for maintaining the virus in the herd.
Emergence of OvHV-2 in boars that had no known contact with sheep was surprising, especially given the possibility of venereal transmission through contaminated semen.
The vasculitis lesions were strikingly similar to those observed in cattle with MCF caused by OvHV-2 or alcelaphine herpesvirus 1.
Although horses are not considered susceptible to OvHV-2, histopathologic findings in this case were consistent with MCF-like lesions.
DNA was extracted from these samples, and PCR was performed to detect members of the MCFV group, including OvHV-2 (5), caprine herpesvirus 2 (6), and alcelaphine herpesvirus 1 (7).
Considering that sheep and goats are the most important natural reservoirs of OvHV-2 (6), these results support the notion that infected goats were the most likely source of infection for horses in this outbreak.
To further support this diagnosis of OvHV-2 infection, we attempted to detect viral DNA in the vascular wall of the foal's hepatic arterioles that contained fibrinoid necrotizing lympho-histiocytic vasculitis by using laser capture microdissection on sections stained with hematoxylin and eosin (10).