Author
 |
King, Daniel |
|
Submitted to: Merck Veterinary Manual
Publication Type: Book / Chapter Publication Acceptance Date: 5/19/2008 Publication Date: 10/15/2010 Citation: King, D.J. 2010. Newcastle disease. In: Kahn, C.M., editor. Merck Veterinary Manual. 10th edition. Whitehouse Station, NJ: Merck & Co., Inc. p. 2457-2458. Interpretive Summary: Newcastle disease (ND), called exotic Newcastle disease (END) in the U. S., continues to be a major threat to the poultry industry. That threat is seen in the form of production losses in infected flocks and trade restrictions that impact noninfected flocks in the same zone or region of a country. The clinical forms of ND remain unchanged from descriptions of the virulent forms of the disease first described in the 1920s to subsequent identification of infections with low virulence Newcastle disease virus (NDV) strains reported 20 to 30 years later. However, the international standards for characterization of isolates have changed to include classification by molecular techniques that expedite diagnosis and differentiation of virulent NDV isolates, the cause of notifiable disease, from low virulence NDV strains that are endemic in many poultry populations and are not the cause of notifiable disease. The new standards are no longer based on classifying NDV as lentogenic, mesogenic, or velogenic reflecting increased levels of virulence for chickens, but separate them into virulent, those viruses previously classified as mesogens and velogens, and of low virulence, the lentogens. Technical Abstract: Newcastle disease (ND), referred to as Exotic Newcastle disease (END) in the U. S., is an acute viral disease of domestic poultry and many other bird species and a recognized worldwide problem. Occurrence of END is due to an infection with virulent strains of Newcastle disease virus (NDV) and is a notifiable event, with subsequent trade restrictions. The clinical signs observed vary with the virulence of the infecting NDV strain, the avian species infected, and the predilection of the infecting strain for the respiratory, digestive, and/or nervous systems. Vaccination of poultry can control the occurrence of clinical disease, but does not prevent the infection of vaccinated birds. Infections with virulent NDV do not produce clinical disease in all bird species. Consequently, the diagnosis of END may require laboratory evaluation of virus isolates from infected birds rather than depending solely on the occurrence of severe clinical disease. |
