21 Sunday July 2019
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Newcastle Disease in Poultry

Newcastle disease is an infection of domestic poultry and many other bird species with virulent Newcastle disease virus (NDV). It is a worldwide problem that presents primarily as an acute respiratory disease, but depression, nervous manifestations, or diarrhea may be the predominant clinical form. Severity depends on the virulence of the infecting virus and host susceptibility. Occurrence of the disease is reportable and may result in trade restrictions.

Etiology and Pathogenesis

NDV, synonymous with avian paramyxovirus serotype 1 (PMV-1), is an RNA virus and the most important of the 9 known PMV serotypes as a pathogen for poultry. The original classification of NDV isolates into 1 of 3 virulence groups by chicken embryo and chicken inoculation as virulent (velogenic), moderately virulent (mesogenic), or of low virulence (lentogenic) has been abbreviated for regulatory purposes.Velogens and mesogens are now classified as virulent NDV (vNDV), the cause of Newcastle disease and reportable infection, whereas infections with lentogens, the low virulence NDV (loNDV) widely used as live vaccines, are not reportable. Clinical manifestations vary from high morbidity and mortality to asymptomatic infections. The severity of an infection is dependent on virus virulence and the age, immune status, and susceptibility of the host species. Chickens are the most and waterfowl the least susceptible of domestic poultry.

Epidemiology and Transmission

Virulent NDV strains are endemic in poultry in most of Asia, Africa, and some countries of North and South America. Other countries, including the USA and Canada, are free of those strains and maintain that status with import restrictions and eradication by destroying infected poultry. Cormorants, pigeons, and imported psittacine species have also been sources of vNDV