NEWCASTLE-DISEASE VACCINES

Newcastle disease (ND) is a worldwide problem with severe economic imp lications, affecting chickens, turkeys and other birds. Newcastle dise ase virus (NDV), a member of the Paramyxoviridae group can cause disea se of diverse severity in accordance with environmental factors. NDV s trains are classified according to their virulence into three categori es. The lentogenic strains are very mild and naturally inhabit healthy flocks. They can be used as live vaccines even for young chicks. Kill ed vaccines can be produced from the same viruses following inactivati on. Mesogenic ND viruses, which cause mild or inapparent respiratory i nfections, have recently been banned in many countries even for killed vaccine production due to fears of disease emergence. Velogenic strai ns are the causative agents of the disease and can be used for the pur pose of vaccine challenge test. Production and use of Newcastle diseas e vaccines are discussed in this review. (C) 1998 Elsevier Science Inc .