By Agu, Anthony Onwubiko
Velogenic Newcastle disease (ND) is a major disease of commercial
and village poultry in Afiica and Asia. Studies of the sequential pathogenesis
of ND under experimentally controlled con&tions have been limi tecl. A flock
of 160 6-week old cockerels, not vaccinated against any disease, was
inoculated intramuscularly with a local Nigerian isolate ofvelogenc ND virus
(NDV) (C'GF-1). Another group of 80 cockerels was inoculated with
phosphate buffered saline ocly and kept as uninfected control. On day 3
post inoculation (PI) the infected birds came down with dullness, drop in
feed and water consumption. Morbidity was 100% by day 4 PI and clinical
signs included grecnish diarrhoea, paralysis and opisthotonus. Torticollis
was observed from clay 7 PI. Improvement in the clinical signs was obsenwd
on day 10 PI and hy day 18 PI only torticollis persisted in some of the birds.
The major gross lesions were petechiation of the proventricular mucosa,
sharply demarcated button-like haemorrhagic ulcers i~i \he snlilll illtestines
and swollen, haemorrlzagic and cheesy caceal tonsils. Bursa of Fabricius,
thymus and spleen were atrophic but by day 20 PI these organs were almost
regaining their nonrial sizes. Other organs showed congestion, haenlorrhage
and oedema. Histop~~thological sections of the lymphoid organs showed
severe lyrnphocytolysis necrosis and depletion Sollwed la tcr by repopulation.
Rend epithelium ;.;as pylaotic. Lesions observed in the brain inlcuded
endotheliosis, peiivasculx lyrnphocitic cuffing, gliosis and hyperaernia.
Oedema and severe lymphocytic infilteration were observed,in the n~eninges.
Infected birds showed increased haemagglutination inhibition (HI) antibody
titres on days 7 and 20 PI. The uninfected birds presented neither clinical
signs, lesions nor seroconversion.
From the above observations it is suggested that the button-like
haenlorrhagic ulcers of the small intestines transiet atrophy of thymus and
petechiation of proventr-ic~ilar mucosa can be veiy useful in the held
diagnosis of ND.