Malignant Catarrhal Fever Viruses in Tennessee Ruminants

Malignant catarrhal fever (MCF) is a lymphoproliferative and inflammatory syndrome affecting primarily ruminant species. The disease, which is often fatal, is most often described as affecting bovids and cervids. No vaccines are available for prevention of MCFV infection. The primary method to control spread of disease is to prevent contact between carriers and clinically susceptible species. There is no known method to control infection of malignant catarrhal fever virus-white-tailed deer variant (MCFV-WTD), as the carrier animal of this virus is unknown.

To determine the prevalence of malignant catarrhal fever viruses in Tennessee ruminant populations, blood and/or lymph node samples were collected from farms, animal processing and disposal facilities, and hunter check-in stations from 2006-2008 from several species of animals including cervids, cattle, and goats. Strain-specific real time PCR was developed to detect ovine herpesvirus-2 (OvHV-2), caprine herpesvirus-2 (CpHV-2), and MCFV-WTD DNA. MCFV DNA was detected in all species of ruminants sampled. Although disease related to infection with MCFV-WTD and CpHV-2 has not been reported in Tennessee cattle or cervid populations, MCFV-WTD DNA was detected in 3 percent of cervid samples, and MCFV-WTD and CpHV-2 DNA was detected in 27 and 3 percent respectively of cattle samples from animal disposal facilities that process dead or debilitated animals. One hunter harvested deer (n=781) and 25 cattle (n=165) tested from animal disposal facilities were positive for OvHV-2 DNA.

This study demonstrated that healthy cattle and cervids can be infected with OvHV-2 and MCFV-WTD without apparent disease, and dead or debilitated cattle were infected with OvHV-2, MCFV-WTD and CpHV-2 at a higher percentage than healthy herd animals. Prevalence of CpHV-2 in Tennessee goat populations (7%) was significantly lower than reported in other goat populations (73%). Low prevalence of CpHV-2 in Tennessee goat populations likely explains why no evidence of infection was found in cervids tested, and the low prevalence of CpHV-2 infection in dead or debilitated cattle compared to prevalence of infection with OvHV-2 and MCFV-WTD. The discovery of infection in cattle with CpHV-2 and MCFV-WTD opens a new avenue of investigation into the pathology and virulence of MCFV’s in domestic cattle.