Neurotoxicose em bovinos associada ao consumo de bagaço de malte contaminado por Aspergillus clavatus

Abstract

Two outbreaks of a neurological disease affecting herds of dairy cattle that were fed moldy beer residues contaminated with Aspergillus clavatus in the county of Viamão, Rio Grande do Sul, Brazil, are described. The morbidity of both outbreaks was 30% and the lethality 50% and 100%. The clinical course varied from 5 to 64 days. Only one of the animals that recovered from the disease remained with slight locomotor sequels. Clinical signs were predominantly locomotor and included muscle tremors of varied intensity, hyperesthesia and progressive posterior ataxia, paresis and paralysis with knuckling of fetlocks of the hind limbs. Gait abnormalities were more pronounced after exercises which in general led to falling down. There was also reduced milk production, but appetite and water intake were maintained until close to death or euthanasia. From five cattle necropsied, two showed macroscopic lesions characterized by necrotic changes and mineralization in pelvic muscles and thoracic limbs. The main histological findings consisted of chromatolytic neuronal degeneration and necrosis in selected nuclei of the brain stem, the ventral horn of the spinal cord, and of the trigeminal, stellate celiac and spinal ganglions. In two cattle there was wallerian degeneration in dorsal funiculi of the spinal cord and ischiadic and fibular nerves. The diagnosis was based on epidemiological data, clinical signs, necropsy findings, histological lesions and mycological examination. Epidemiologic, clinical and pathologic aspects, pathogenetic mechanisms and differential diagnoses are discussed.