Reed Neurological Research Center, UCLA School of Medicine, Los Angeles, California

Neurological lesions in chickens experimentally infected with virulent Newcastle disease virus isolates

Distribution, character, and severity of lesions were evaluated in tissues from the central nervous system of chickens inoculated with 10 different Newcastle disease virus (NDV) isolates: CA 1083, Korea 97-147, Australia (all velogenic viscerotropic), Texas GB and Turkey North Dakota (both velogenic neurotropic), Nevada cormorant, Anhinga and Roakin (all mesogenic), and B1 and QV4 (lentogenic). Tissues for the present study included archived formalin-fixed, paraffin-embedded brain (all strains) plus spinal cord (two strains). Encephalitis was observed in all velogenic viscerotropic and velogenic neurotropic strains, and in some mesogenic strains. In general, the encephalitic lesions began at 5 days post infection, with more severe lesions occurring around 10 days post infection. At this time point, especially in the grey matter of the brain, cerebellum and spinal cord, there were neuronal necrosis, neuronal phagocytosis, and clusters of cells with microglial morphology. Axonal degeneration and demyelination was also observed. Immunohistochemistry (IHC) for viral nucleoprotein confirmed the presence of virus. In the areas of encephalomyelitis, IHC for CD3 revealed that many of the inflammatory cells were T lymphocytes. IHC using an antibody for glial fibrillar acid protein showed reactive astrogliosis, which was most pronounced at the later time points.

Newcastle disease: a review of field recognition and current methods of laboratory detection

Newcastle disease (ND) remains a constant threat to the poultry industry and is a limiting disease for poultry producers worldwide. The variety of clinical presentations and the emergence and spread of new genetic variants make recognition and diagnosis challenging. The current review details the pertinent features of the clinicopathologic disease in the main susceptible species, including chicken, turkey, duck, goose, pigeon, and other birds such as cormorants, psittacines, and canaries. Furthermore, the available and emerging laboratory diagnostic methodologies for the detection and typing of the virus are reviewed, including traditional techniques such as virus isolation and immunohistochemistry as well as rapid procedures based on molecular tools, such as real-time polymerase chain reaction, gene sequencing, and microarrays. The relevant genetic variability of ND viruses probably represents the major limitation in the validation and application of the current, advanced diagnostic molecular techniques. This underscores the importance of a multidisciplinary and comprehensive diagnostic approach, which should include, next to the new generation assays of the genomic era, the more traditional techniques such as histopathology, immunohistochemistry, and virus isolation.

Response of chickens to infection with Newcastle disease virus isolated from a guinea fowl

An isolate of Newcastle disease virus obtained from a guinea fowl was characterized as a viscerotropic velogenic strain based upon pathogenicity index studies. Following inoculation of the viral isolate oronasally into 3-week-old chickens, clinical signs appeared after an incubation period of 4-5 days and included dullness, depression, dyspnoea, diarrhoea and leg paralysis. The virus caused a mortality of 56% with haemorrhages at the tip of the glands of the proventriculus and caecal tonsil. Histopathological changes were prominent in the lymphoid organs, being characterized by depletion, degeneration and necrosis of the lymphoid tissues. The brain was the first organ affected, with changes being noticed 3 days after infection. Isolation of virus from various organs was more frequent from 5 to 10 days after infection, but the virus persisted in some of the organs until 21 days after infection. In spite of the high mortality, a good immune response was elicited by the isolate, as was evident from the antibody titre.

Newcastle disease vaccines

Newcastle disease (ND) is a worldwide problem with severe economic implications, affecting chickens, turkeys and other birds. Newcastle disease virus (NDV), a member of the Paramyxoviridae group can cause disease of diverse severity in accordance with environmental factors. NDV strains are classified according to their virulence into three categories. The lentogenic strains are very mild and naturally inhabit healthy flocks. They can be used as live vaccines even for young chicks. Killed vaccines can be produced from the same viruses following inactivation. Mesogenic ND viruses, which cause mild or inapparent respiratory infections, have recently been banned in many countries even for killed vaccine production due to fears of disease emergence. Velogenic strains are the causative agents of the disease and can be used for the purpose of vaccine challenge test. Production and use of Newcastle disease vaccines are discussed in this review.

Paramyxovirus-1 in feral pigeons (Columba livia) in Ontario

Paramyxovirus-1 (PMV-1) infection was diagnosed in racing pigeons in Ontario during 1985, but it was not until January 1989, that the virus was isolated from feral pigeons (Columba livia) in this province. During an 18 month period beginning January 1988, a total of 43 feral pigeons was submitted to the Wildlife Diseases Laboratory, Pathology Department, Ontario Veterinary College. A history of neurological signs accompanied most of the birds. Tissues from 29 birds were submitted for PMV-1 isolation. Allantoic inoculation of embryonated chicken eggs yielded PMV-1 in 10 of the pigeons submitted. On the basis of histological criteria, we believe that 12 other birds were also infected with PMV-1.Gross pathological changes were unremarkable. Lymphplasmacytic interstitial nephritis was observed histologically in all birds from which PMV-1 was isolated. Other lesions seen, in decreasing frequency of occurrence, were lymphoplasmacytic interstitial hepatitis and multifocal hepatic necrosis, lymphoplasmacytic interstitial pancreatitis, nonsuppurative encephalitis and myelitis.The existence of PMV-1 in feral pigeons poses a potential threat to the poultry population since there is ample opportunity for mingling with poultry under open housing management. There is also a concern that pigeons may harbor the virus, perhaps in the kidney, and become chronic carriers and potential long-term disseminators of the disease.