Low dose velogenic viscerotropic Newcastle disease virus infection caused 30% mortalities in Anak broilers but none in Lohmann Brown layer chickens

摘要

The aim of this project was to find out the comparative susceptibilities of broilers and layer chickens to a low dose of velogenic viscerotropic Newcastle disease virus (vvNDV) infection using mortalities as the main indicator. Five weeks old Anak broilers and Lohmann Brown layer chicks were inoculated with vvNDV. The birds were monitored daily for clinical signs and disease evolution was evaluated. Clinical signs consisting of depression and diarrhea appeared at 3 days post-inoculation (DPI) in broilers and at 2 DPI in layer chickens resulting in total mortalities of 30% and 0% in broilers and layer chickens, respectively. Weight loss was statistically, significant in infected broilers on 3 to15 DPI ( p ?0.05), while no such difference was observed in the weight of infected layer chicks ( p ?0.05). Macroscopic lesions were similar but more severe in broilers compared to layer chickens and included proventricular haemorrhages, intestinal and caecal ulcers. But atrophy of the bursa, spleen and thymus and necrosis and depletion of lymphocytes in the three organs were severe in the infected broilers and pullets Antibody response was significantly ( p ?0.05) higher in the layer chickens but virus isolation was more frequent in the broilers.