Comparison of Newcastle disease viruses isolated from cormorants in Canada and the USA in 1975, 1990 and 1992.

Seventeen Newcastle disease virus (NDV) isolates obtained from cormorants, turkeys, a pelican, and a gull in Canada and the USA collected in 1975, 1990 and 1992 were analyzed for relatedness by monoclonal antibody profiling. In addition, nucleotide sequence analysis was performed in two areas of the fusion (F) gene for 5 of the isolates. No difference in the antigenicity of these 17 viruses, as determined by monoclonal antibody binding patterns, was seen. The amino acid sequences obtained via nucleotide sequencing at the cleavage site of the F protein showed that all the isolates tested had two pairs of basic amino acids immediately upstream of the cleavage site, and a phenylalanine residue at the N-terminus of the F1 protein, which is consistent with velogenic NDV. The deduced amino acid sequence obtained at the cleavage site of the F protein from 6 of the isolates was virtually identical regardless of the species, year of isolation, or location. However, the 1975 cormorant isolate showed marked differences from the 1990-1992 isolates in the nucleotide and deduced amino acid sequence of the F gene signal region. These data indicate that the 1990 and 1992 outbreaks were caused by the same epizootic virus and further suggest that the population of NDV in these wild birds may be very stable. The belief that the velogenic NDV circulating in cormorants in 1992 was transmitted into the free-ranging turkey flocks located near the cormorants in North Dakota is supported by the present study in which no distinction could be made between the viruses isolated from turkeys or wild birds.     

Newcastle disease.

Since 1926, there have been three epizootics of ND. The latter two have been directly linked with psittacine species and Racing Pigeons. The modern poultry industry is extremely vulnerable to the effects of NDV, once it gains entry to any facet of the industry. Consequently considerable expense and effort are expended to keep the virus at bay. The main threat continues to come from psittacine species and racing pigeons. The considerable international trade in these birds, together with rapid air transport, can allow virulent NDV to gain entry to a country while exotic birds are incubating the disease. It is hoped that quarantine barriers and requirements will prevent the virus from entering a country, but smuggling continues and constitutes the biggest risk. Domestic avian pets are also vulnerable to the virus. It is hoped that new in vitro testing procedures, such as monoclonal antibody and oligonucleotide fingerprinting techniques, may be used to identify rapidly and characterize emergent virulent strains, so that appropriate measures may be taken to prevent infection of commercial poultry and domestic pets.     

Isolation of Newcastle disease virus and Salmonella typhimurium from the brain of double-crested cormorants (Phalacrocorax auritus)

Avian paramyxovirus type 1 (Newcastle disease virus) and Salmonella typhimurium were isolated from the brain and lung tissues of double-crested cormorants (Phalacrocorax auritus) from Lac Canard, Alberta, Canada. More than 100 birds died during this outbreak in 1999. Affected birds presented signs of central nervous system disease characterized by unilateral wing and leg paralysis. Other geographic locations in the provinces of Alberta and Saskatchewan have reported cases of cormorants suffering from diseases with signs compatible with Newcastle disease. The virus isolated in the 1999 outbreak was characterized as mesogenic. These findings suggest that other pathogens, like S. typhimurium, may influence the clinical presentation of disease caused by mesogenic strains of Newcastle disease virus in cormorants.     

Epizootiology of Newcastle disease in waterfowl.

Antibodies to Newcastle disease virus (NDV) as measured by hemagglutination-inhibition and virus-neutralization tests were detected in 40/236 Canada geese captured while in their southward migration or in their wintering grounds. Antibodies were also found in 37/267 wild ducks and in 20/31 domestic geese. Adult geese were readily infected by several routes. Inapparent disease usually resulted, and only 1/13 cases were fatal. Goose embryos responded differently to inoculation with selected NDV strains than did chicken embryos of comparative developmental stages. Some goslings that hatched from inoculated embryos died and were found to have virus, whereas others survived and developed active antibodies. Four strains of virus isolated from migratory ducks of the Pacific flyway were characterized. All 4 strains were lentogenic but differed from lentogenic strains prevalent in chickens by being thermostable. It is proposed that wild waterfowl neither receive their ND infection from domestic poultry nor pass their disease to poultry. The virus reservoir probably exists in nature.     

Thermostable Newcastle disease vaccines in Tanzania.

The V4 thermostable Newcastle disease vaccine was tested under village conditions in Central Tanzania. The vaccination regimes were four vaccinations by eye drop (eye drop group), one vaccination by eye drop followed by three vaccinations by drinking water (drinking water group), one vaccination by eye drop followed by three vaccinations with vaccine supplied on boiled sorghum (food vaccine group) and no vaccine (control group). Antibody responses in the eye drop and drinking water groups suggested that at least 70% of the chickens would be protected against challenge with virulent virus. In both groups, eight of the 11 chickens survived laboratory challenge. Only three of the 11 chickens in the food vaccine group resisted challenge, and none of the 10 control chickens.     

Gordon Memorial Lecture. Newcastle disease

1. In this paper several historical and contemporary aspects of Newcastle disease (ND) are reviewed, with particular reference to the greater understanding which modern techniques have allowed. 2. Virulent ND viruses were generally thought to have emerged in 1926 as a result of transfer from a wild bird host reservoir but there is evidence that the virulent virus may have existed in poultry before 1926. Recent findings suggest that the virulent virus may emerge in poultry as a result of mutations in viruses of low virulence. 3. The history of ND in Great Britain reflects the four known panzootics that have occurred and serves as a model for the impact this disease may have on poultry populations. 4. Attempts to control and eradicate ND are not as straightforward as it may appear; in particular vaccination, while preventing deaths and disease, on challenge may not prevent virus replication and could therefore lead to the virulent virus becoming endemic. 5. Village chickens are extremely important assets in most developing countries, representing a significant source of protein in the form of eggs and meat but endemic ND can cause mortality of up to 60% in village chickens.     

Wintering of neurotropic velogenic Newcastle disease virus and West Nile virus in double-crested cormorants (Phalacrocorax auritus) from the Florida Keys

During November 2002, six double-crested cormorants (DCCs; Phalacrocorax auritus) were found moribund in Big Pine Key, FL, exhibiting clinical signs indicative of neurologic disease. Postmortem diagnostic evaluations were performed on two adult birds. Virulent Newcastle disease virus (NDV) was isolated from a cloacal swab from cormorant 1. West Nile virus (WNV) was isolated from the brain and lung of cormorant 2. Nucleotide sequence analysis of a portion of the fusion (F) protein gene of the NDV cormorant isolate revealed it shared a 100% deduced amino acid identity with only two viruses: the 1992 epizootic cormorant isolate from Minnesota and the 1992 turkey isolate from North Dakota. The epidemiologic significance of the recognition of virulent NDV on cormorant wintering grounds during a nonepizootic period, in addition to the potential implications of the concurrent isolation of NDV and WNV from cormorants, is discussed.     

Exotic Newcastle disease

Exotic Newcastle disease (END) is a virulent strain of avian paramyxovirus-1. This virus has devastated the poultry industry in many countries. As a result, strict international regulations are in place to control the movement of exotic birds, poultry, and poultry products to prevent the introduction of this disease into countries where it has been eradicated. When END is introduced to a naı̈ve, unvaccinated population of poultry, mortality may reach 100%. Signs in chickens will depend on the strain of END involved. However, this disease should be suspected in any outbreak of disease in poultry where there is high mortality and respiratory, gastrointestinal and/or central nervous system signs are observed. In the most recent END outbreak in the United States, many birds had edematous heads, cyanosis, and diphtheritic lesions of the trachea, oral cavity, and esophagus. Signs in companion birds are variable and often nonspecific. Practitioners, however, should suspect this disease in parrots, particularly Amazon parrots, if the sick bird is of questionable origin and over the course of the disease develops signs related to the central nervous system. Efforts to keep END out of the United States have been largely successful; however, on repeated occasions in the last 30 years, END has entered the United States through the illegal transport of fighting chickens and psittacine birds. In two cases, END has made it into commercial poultry operations, resulting in the slaughter of millions of birds and a significant economic impact to poultry and exotic bird producers. Education about this disease, strict biosecurity measures, and continued vigilance will be necessary to prevent future outbreaks of END.     

Characterisation of Newcastle disease viruses isolated in India.

Eleven Newcastle disease virus (NDV) isolates obtained from outbreaks of disease in chickens (9) and Japanese quail (2) in Tamil Nadu, India were characterised in pathogenicity tests, antigenically, using mouse monoclonal antibodies (MAbs), and other established tests devised to distinguish between different strains. All 11 isolates were shown to be highly virulent for chickens. In indirect immunoperoxidase tests used to assess the ability of a panel of 28 MAbs to bind to infected cell cultures, 10 of the isolates showed an identical reaction pattern, the other isolate (No. 4) failed to react with one MAb which bound to cells infected with the other isolates. Isolates 9 was unstable at pH 3 while the other 10 were stable. All other properties were shared by the 11 isolates.     

Exotic Newcastle disease in a game chicken flock.

A sudden increase in mortality, preceded by a short history of respiratory signs and diarrhea, occurred in a backyard flock of 48 game chickens in the Central Valley of California. Necropsy findings included severe generalized linear hemorrhages and/or ulcers in the digestive tract, larynx, and trachea. Histology revealed severe multifocal hemorrhages and necrosis in the mucosa of the respiratory and digestive tracts, vasculitis, and necrosis of lymphoid tissue. The birds were serologically negative to Newcastle disease virus; this was consistent with an acute infection. The avian paramyxovirus type 1 isolated was characterized as velogenic viscerotropic Newcastle disease virus. A thorough epidemiologic investigation was carried out, and no other premises were found to have birds with clinical signs or evidence of exposure. The entire outbreak was limited to the original backyard flock and resolved within 14 days of the onset of clinical signs.     

Efficacy of a commercial Newcastle vaccine against velogenic viscerotropic Newcastle disease virus.

Effects of parental immunity and method of vaccination were studied in broiler chickens vaccinated with a commercial LaSota vaccine and challenged with the Fontana strain of velogenic viscerotropic Newcastle disease (VVND). Immunity was satisfactory from all methods of vaccination used.