Sciensano hosts the national reference laboratory (NRL) for the Newcastle disease virus (ND).
Newcastle disease
Newcastle disease
Newcastle disease (ND), also known as avian pseudopest or paramyxovirosis, is a highly contagious viral disease that affects many bird species (wild and domesticated). It can be caused by a variety of strains. The symptoms of this disease vary depending on the viral strain and the affected poultry species. In case of very aggressive strains, the disease can lead to a high mortality. It is present everywhere in the world.
Newcastle disease and animals
Transmission
Newcastle disease virus (NDV) is spread by direct contact between infected birds or by indirect contact with contaminated substrates (such as water or food contaminated with infected faeces). The disease is highly contagious and can rapidly become epizootic (i.e., animal epidemic) if strict, rapid and effective control measures are not implemented.
Symptoms
The Newcastle Disease Virus (NDV) can infect more than 200 different bird species. An infection with this virus causes symptoms such as:
- depression
- diarrhea
- exhaustion
- edema of the head and
- barbels.
In general, respiratory, digestive and nervous symptoms can be observed.
However, the virulence of this virus and the clinical symptoms of the disease may vary, depending on the host and strain involved.
Newcastle disease and humans
Humans are not sensitive to the disease. Some isolated cases of conjunctivitis have been reported, but they are rather limited and benign.
Notifiable disease?
Newcastle disease (ND) is a disease that requires mandatory notification to the local FASFC control unit. In view of its highly contagious nature, strict embargoes on the trade in poultry products are introduced at international level. In addition to good biosafety practices, the ND control mainly consists of the compulsory vaccination in Belgium of poultry and the slaughter of infected birds and those who may be infected (protection zone).
Information for health professionals
To limit the spread, several very strict health measures are taken, such as:
- set up warning systems
- preservation in quarantine or in zones (protection, monitoring, buffer)
- destroy contaminated or possibly exposed poultry
- stop or control the transport of poultry, or materials in contact with those.
Vaccination against Newcastle disease
Currently, and depending on the disease situation and regulations, vaccination programs against ND use 2 strains:
- lentogenic (weakly virulent) strains, which can either be inactivated (killed) or weakened (alive) to protect the vaccinated birds as well as possible with as few side effects as possible.
- mesogenic strains (with moderate virulence).
In addition, vaccination programs can also differ between poultry breeds. In general, post-vaccination serology is used to confirm the successful administration of the vaccine and an adequate immune response of the vaccinated bird.
The current vaccination strategies mainly protect against morbidity (frequency of disease) and mortality (frequency of death). They also significantly reduce the occurrence of the disease and the viral re-excretion, but can not exclude them. This limitation is a crucial element in controlling the spread of the disease.
Limitation of the effectiveness of the vaccine
One of the most important considerations in immunization programs is the degree of maternal immunity in young chickens. This immunity can vary considerably from farm to farm and individually between chickens.
Another limitation of the effectiveness of the vaccine is that the current vaccines are less effective against the viruses that are currently circulating. However, they protect very well against isolated viruses in earlier epizootic diseases.