Przypadek zakaznego zapalenia mozgu i rdzenia kregowego u kurczat brojlerow

The study presents a case of infectious avian encephalomyelitis (AE) in a commercial broiler’s flock. The chickens (line Ross 308) at the age of 16 days demonstrated typical nervous symptoms: ataxia, unsteady gait together with laying on their sides. These signs were observed in the majority of the flock (50-60%) with the most severe outbreak between 16 and 22-days-of-age. At this period we did not observed an atypical mortality rate for the disease but there was a very high selection rate (3% within 6 days). In the necropsy only enlarged cloaca and an excess of urates in ureter were observed. The principle histopathologic changes were distributed throughout the central nervous system as manifested by gliosis, perivascular cuffing with lymphocytes and neuronal degeneration. These signs were typical for AE. Serological assays proved that 45% of 1-day-old chicks were seronegative against AE. This meant that broiler breeders were not vaccinated properly. Birds at the age of 3 weeks were seronegative, but at the age of 6 weeks, 5% of the flock had specific antibodies against AE. All these data: clinical signs, gross lesions, histopathology and serological examination, confirmed that the losses to the flock were caused by avian encephalomyelitis virus.