Outbreak of bovine herpetic meningoencephalomyelitis in Southern Brazil

ABSTRACT

Background: Herpetic meningoencephalitis is an infectious contagious disease worldwide distributed, most often caused by bovine alphaherpesvirus type 5 (BoHV-5), although bovine alphaherpesvirus type 1 (BoHV-1) may occasionally be the causative agent. The disease is characterized by subacute to acute clinical onset, often affecting animals submitted to stressful situations. Clinical signs are mainly neurologic due to meningoencephalitis and cortical necrosis. The involvement of the spinal cord has also been reported, however in BoHV-1 associated disease only. The aim of this report is to describe an outbreak of bovine meningoencephalomyelitis associated to BoHV-5.Case In August 2017, nine 1-year-old calves died in a beef cattle farm with a flock of approximately 400 bovines. The animals presented neurological clinical signs characterized by excessive salivation, nasal and ocular discharges, incoordination, apathy, head tremors, head pressing, wide-based stance, recumbency followed by convulsions and paddling. According to the owner and referring veterinarian, affected animals displayed severe clinical signs with rapid progression and often leading to death in up to seven days. Four of these calves were submitted for necropsy, and gross lesions were present in the brain, characterized by mild to moderate multifocal hemorrhagic and soft areas. On cut surface, extensive areas of dark brown discoloration and malacia were observed. Histologically, lesions were characterized by extensive areas of liquefactive necrosis in the cerebral cortex grey matter, associated with inflammatory infiltrates composed of neutrophils, lymphocytes, plasma cells and foamy macrophages, as well as multifocal to coalescing areas of hemorrhage and fibrin deposition. Intranuclear eosinophilic inclusion bodies were rarely observed in neurons and astrocytes. On leptomeninges, there was diffuse inflammatory infiltrates of lymphocytes and plasma cells.[...]