Newcastle Disease—Pathogenesis and Diagnosis

Discussion and SummaryThe pathogenesis and the gross pathology resulting from infection with viscerotropic velogenic Newcastle disease virus pathotypes, generally are characteristic in a susceptible avian population on a single premises or in one geographical region. The other forms of velogenic Newcastle disease and the disease caused by mesogenic or lentogenic types of the virus generally do not present characteristic symptoms and lesions.In geographical areas where virulent Newcastle disease is usually absent, the first appearance or reappearance of the disease has led to a number of false diagnoses, especially in the initial stages of an outbreak. The resulting delay can be very damaging to the poultry industry. In this situation, and because usually there is no gross nor microscopic pathognomonic lesion, prompt and accurate laboratory diagnosis is essential. The control of Newcastle disease and the reduction in the economic effects depend to a great extent on the speed in which a definitive diagnosis can be made and transmitted into prompt measures in the field. Under favourable conditions, it is possible to isolate and identify NDV in 48 hours.The gross and laboratory diagnosis of the many forms of Newcastle disease and its virus cannot be described in detail in a single review of this type. The clinical symptoms, the gross pathology and the different laboratory techniques available, require specialized study and knowledge. The main purpose of this paper is to outline the limitations of gross pathology, to caution against errors in field diagnosis and to emphasize the need for modern laboratory techniques and the speed, in hours, in which Newcastle disease virus can be identified provided simple but reliable methods are available.For the above reasons, it is considered more useful to provide a list of publications which describe aspects of the broad subject of the pathogenesis and diagnosis of Newcastle disease.