Abstract & Overview
Newcastle disease is a contagious bird disease affecting many domestic and wild avian species. It is a zoonotic disease with widespread distribution. It is caused by avian Paramyxovirus serotype 1 virus which, with viruses of the other eight serotypes (avian paramyxovirus1-9), has been placed in the genus Avulavirus, sub-family Paramyxovirinae, family Paramyxoviridae. Virulent ND virus strains are endemic in poultry in most of Asia, Africa, and some countries of North and South America. Other countries, including the United States of America and Canada, are free of those strains in poultry. The strain of Newcastle pathogenicity can be classified into five pathotype: Asymptomatic enteric strain; Lentogenic strain; Mesogenic strain; Viscerotropic velogenic strain and Neurotropic velogenic strain. Clinical signs are extremely variable depending on the strain of virus, species and age of bird, management, concurrent disease, and pre-existing immunity caused by Paramixovirus with worldwide distribution affecting chickens of all age groups.