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Together with Avian Influenza, Newcastle disease virus (NDV) represents one of the two most significant avian diseases. This is possibly due to their rapid spread globally and the high mortalities they cause.
Outbreaks are notifiable to the World Organization for Animal Health (OIE). They are also published in different media to prevent their spread to the poultry industries of other countries.
NDV is classified in the Paramyxoviridae family, genus Avulavirus. The viruses are classified into different groups according to their pathogenicity.
The disease
In general, the disease can be observed in two different forms: When infection is caused by viruses of low virulence, the clinical signs include respiratory problems with rapid spread and lesions in the respiratory system, including the air sacs.
This causes a reduction in the productive parameters of the birds and an increase in the percentage of discarded birds in slaughterhouses.
Infection with virulent viruses: The symptoms are varied depending on the type of virus causing the outbreak, therefore, anything from conjunctivitis, dyspnea, inflammation around the eyes, diarrhea, severe depression to death can be observed.
Nervous signs like torticollis, and wing & leg paralysis may be seen in the final stages of the disease. Production is also significantly affected in adult birds. Deformed eggs with weak shells, pigmentless shells are common, as well as a general drop in lay. Mortality in young birds can reach 100%.
Transmission
The virus is released through the respiratory and intestinal tracts and is transmitted to other birds by aerosol or by ingestion of viral particles present in the feces and in the environment of the houses. The virus can also be transmitted by direct contact with infected birds, contaminated feed, objects and personnel, etc.
The incubation period varies from 3 to 8 days and the clinical consequences depend on factors such as:
Virus type
Viral load
Vaccination plan and type of vaccines
Immune status of birds
Diagnosis
Macroscopic lesions are variable depending on the type of virus affecting the birds. In some cases the lesions may be similar to those of avian influenza. Therefore, definitive diagnosis requires the identification of the virus either by isolation or by molecular methods.
Differential diagnosis
Newcastle disease virus must be differentiated from avian influenza, as these virus cause similar clini...
