Malignant catarrhal fever (MCF) is a highly fatal viral disease of cattle and other susceptible species of ruminants that occurs sporadically and is characterized by two epidemiological aspects. One is known as wildebeestassociated MCF (WA-MCF), whose agent is Alcelaphine herpesvirus-1, and the other is known as sheep-associated MCF (SA-MCF), whose agent is ovine herpesvirus-2 (OvHV-2). The researchers developed polymerase chain reaction (PCR) assay to detect OvHV-2 genome in three sample groups: (1) Peripheral blood lymphocytes from cattle with clinical signs of MCF (n=15); (2) lymph node and spleen samples from healthy cattle (n=68); and (3) lymph node and spleen samples from adult sheep (n=82). All tissue specimens were collected randomly, and just one sample was taken from each animal. The PCR amplified a specific 422-bp SA-MCFV DNA fragment by pair primers 556 and 755 from samples. Of all 165 specimens, 44 samples had 422 bp SA-MCFV DNA fragment band (26.6%). Of 68 samples from healthy cattle, 20 samples were infected to OvHV-2 genome (29.41%), and of 82 healthy sheep specimens, nine samples were positive (10.98%). According to the data, the present study can confirm at least SA-MCF epidemiological form of the disease in sampling area. However, there may be another form, too. It is significant that infectivity rate of sheep samples was less than cattle, which suggests that healthy cattle are probably as important hidden carriers for OvHV-2 as sheep. In addition, positive lymph node sample rate was more than spleen samples in both groups 2 and 3. It may come from virus tropism to hide in the nearest lymphoid tissue and to cause latent infection.
