Newcastle Disease in Laying Hen Flocks

1. Newcastle Virus

Newcastle disease is caused by a highly infectious virus that affects poultry and other birds. Newcastle virus comes in many strains that are sometimes classified, from "hot to cold", as velogenic, mesogenic, lentogenic and assymptomatic. The cold strains will cause no symptoms while the hot ones can lead to very high mortality in poultry flocks.

2. Signs and Susceptibility to Newcastle Disease

In unvaccinated birds, or in face of a strong challenge, Newcastle disease can cause a drop in egg production, decrease in egg white thickness and an increase in abnormal egg shells. In vaccinated laying hens, mortality may not increase in face of a challenge. Young pullets tend to be more severely affected than older birds and are more likely to die from the disease. In some cases, the virus does not directly kill the birds but makes them more vulnerable to bacteria such as E. coli. Older turkeys and waterfowl tend to be more resistant to the disease than chickens.

The hot strains of Newcastle virus can cause significant mortality and damage the bird's respiratory tract and/or the nervous system. One severe form of the disease, Velogenic Viscerotropic Newcastle Disease or VVND, can cause hemorrhages in the digestive tract. This form of Newcastle disease has been associated with parrots, cockatiels and other exotic birds. All mortality due to hot strains of Newcastle Disease must be reported to the Canadian Food Inspection Agency (CFIA). It is CFIA's responsibility to investigate and recommend action when mortality due to Newcastle disease is suspected.

3. Newcastle Disease in Other Birds

4. Spread of Newcastle Disease

Newcastle disease can be spread to commercial poultry from numerous sources, including: 

1) other poultry and wild birds; 2) other animals; 3) people and equipment
4) airborne particles; 5) contaminated water, feed or grain

The virus can be shed in droppings and manure from infected birds and it can also travel as airborne particles. It is preserved by cold temperatures but may be destroyed by direct sunlight.

5. Diagnosis

If Newcastle disease is suspected, then birds should be submitted to a diagnostic laboratory to rule out diseases which can cause symptoms similar to Newcastle Disease: Infectious Bronchitis, severe Mycoplasma gallisepticum (MG), Infectious Laryngotracheitis (ILT), Avian encephalomyelitis (AE) or vitamin E deficiency. The treatments for these diseases are not all the same and an accurate diagnosis is needed.

6. Blood Sampling

In vaccinated birds, Newcastle disease may appear very similar to a bronchitis challenge in your flock. Blood sampling the birds can help determine whether Infectious Bronchitis or Newcastle disease is present. One set of 20 blood samples should be taken when production starts to drop or mortality starts to increase and another set should be taken four weeks later. If the blood samples indicate that the birds have increased their serum antibodies to protect against Newcastle Disease, the birds likely have been challenged. Blood samples taken prior to the production drop or mortality may also be useful. In flocks that have been injected with killed Newcastle vaccine, these pre-challenge blood samples should be taken six or more weeks after the pullets have been needled.

It is very difficult to interpret blood samples taken from birds which have been boosted with live Newcastle vaccine during lay or injected with killed vaccine as pullets. The live vaccine stimulates the birds to produce antibodies against Newcastle virus and the blood test does not distinguish between antibodies produced in response to a vaccine versus a field challenge. When pullets are injected with killed vaccine, the antibody levels stimulated by the vaccine are very high and the blood test may not be able to detect the increase in levels that occurs if the birds are further challenged.

7. Vaccination

All leghorn pullets are vaccinated against Newcastle disease. Producers wanting extra protection for their flock can have their pullets injected with a killed vaccine at 17 to 19 weeks of age. Another alternative is to "boost" with live vaccine throughout lay. The injection stimulates antibodies against Newcastle disease for the entire laying period and needs only to be given once. Success of the killed vaccine depends on effective priming of the pullets with live vaccine prior to the injection. If the birds are boosted with live vaccine during lay, care must be taken to avoid a strong reaction to the vaccine which could affect production. Most vaccine companies recommend re-vaccinating every 6 to 8 weeks during lay. Prolonging the time between vaccinations further may result in an undesirable reaction to the vaccine. Only use the type of vaccine recommended by your vaccine company or veterinarian. If you are spraying the vaccine, follow the recommendations on type of sprayer and nozzle size.

If you must begin a live boosting program in the middle of a flock, collect blood samples from all ages of birds in the laying barn and check the Newcastle antibody levels. If antibody levels are low, the vaccine is more likely to have a negative effect on the birds. You may want to avoid vaccination unless a high Newcastle risk exists on your farm. To minimize the chance of a strong reaction, vaccine manufacturers often recommend that the first vaccination be delivered in the water instead of with a sprayer. Avoid vaccinating during times of stress in the flock. When you start live vaccination on a multiple age layer farm, remember that the vaccine can spread from barn to barn and it is usually best to vaccinate all barns at the same time.

8. Prevention / Biosecurity

Many steps can be taken to prevent Newcastle disease from infecting your flock: