Pathogenicity of two strains of Newcastle disease virus in the grey-breasted helmet guinea fowl.

Thirty-five 6-week-old guinea fowl keets, seronegative for maternal antibodies to Newcastle disease virus, were infected with Herts strain (33/56) and Kumarov strain of Newcastle disease virus intramucularly (IM) or intranasally (IN). Clinical signs were first noticed four days post infection (PI) in the group infected IM but five days PI in the group infected IN with Herts strain of Newcastle disease virus. These clinical signs were similar in both groups and included anorexia, droopiness, huddling together, greenish diarrhoea and marked cachexia. Prominent nervous signs, including spasms of the head and neck, were observed in groups infected with Herts strain. The major gross lesions observed were emaciation with prominent keel bone, empty intestinal tract and distended gall bladder in most keets. The histological lesions were characterised by meningoencephalitis, necrosis and loss of lymphocytes from splenic and lymphoid aggregates. There was muscular degeneration and necrosis in the gizzard and mild pulmonary congestion and oedema in some keets. Neither gross or microscopic lesions were observed in keets that had received the Kumarov strain.