Evidence of persistent malignant catarrhal fever infection in a cow obtained by nucleic acid hybridisation.

A natural non-fatal case of sheep-associated malignant catarrhal fever in a cow is reported. Viral DNA confirmed by nucleic acid hybridisation and polymerase chain reaction persisted in peripheral blood leukocytes for at least 3 months after the clinical onset of the disease. Concultivation of leukocytes with various cell cultures failed to result in isolation of the virus either by cytopathic effect or by nucleic acid hybridisation.