Pathogen studies of bovine progressive degenerative myeloencephalopathy (weaver) of Brown Swiss cattle

Abstract

Results are given from further studies on the clinical signs and pathology of cattle affected with this disease. Clinical signs of bovine degenerative myeloencephalopathy ("weaver") in Brown Swiss cattle, appear when calves are 6 to 8 months old and progress during the next 12 to 18 months to recumbency. Four basic criteria for diagnosis are: 1. onset of bilateral hind leg weakness and ataxia between 5 and 8 months of age; 2. deficient proprioceptive reflexes, normal motor and sensory reflexes, and no other clinically detectable neurological abnormality; 3. absence of clinically significant skeletal or muscular abnormaltiy; and 4. adherence to familial relationship. There are no gross lesions typical for weavers, and primary microscopic lesions are confined to the central nervous system. Spinal cord lesions consisted of axonal degeneration including spheroid formation, loss of axons and myelin, and vacuolation of white matter due to large, empty intercellular spaces. Lesions were quantitatively similar at all spinal cord levels in the same funiculi. Cerebellar lesions were limited to selective degeneration and loss of Purkinje cells and occasional swelling of Purkinje cell axons in the granular layer of the cerebellar cortex. Progressive degenerative myeloencephalopathy is the single most important genetic disease of purebred Brown Swiss cattle and may be an inherited congenital metabolic defect of axon transport.