Newcastle Disease—A Review of the Geographical Incidence and Epizootiology

SummaryThe geographical incidence of Newcastle disease has changed markedly since 1962. New features have appeared. These include the appearance of a virulent and highly diffusible strain of virus. Another feature present in North and South America has been the occurrence of the classical type of virulent virus, causing marked intestinal lesions.It is clear that more information is needed on the part played by free-flying psittacines and other birds in their native environment.Although the classic methods of spread have been studied, nevertheless, initial outbreaks of undetermined origin have been reported from a number of countries. Whether these outbreaks are the result of infection from free-flying migratory birds has not been determined. Another cause of spread of Newcastle disease virus is the rapid movement by air transport of both domestic poultry and smaller birds caught in the wild.If birds are to continue to be transported in large numbers, corresponding quarantine measures involving strict procedures must be established by the importing countries.