Dexamethasone-induced recrudescence of malignant catarrhal fever and associated lymphosarcoma and granulomatous disease in a Formosan sika deer (Cervus nippon taiouanus).

Malignant catarrhal fever (MCF) was diagnosed in a 2-week-old Formosan sika deer. The fawn had been previously exposed to a clinically normal neonatal wildebeest calf from which alcelaphine herpesvirus-1 was isolated. Alcelaphine herpesvirus-1 was isolated from buffy coat leukocytes and nasal and ocular secretions of the fawn during the acute illness. The fawn clinically recovered after 3 weeks. Virus was not recovered from blood at this time. Dexamethasone, given 4 months after clinical recovery, resulted in reisolation of MCF virus from blood and recrudescence of clinical MCF. The deer was euthanatized. At necropsy, pathognomonic lesions of MCF, granulomatous disease, and malignant lymphoma were observed. Antibodies to bovine leukosis viral antigens were not detected in the serum. The epidemiologic and pathogenetic importance of the findings are discussed.