Newcastle Disease

What is Newcastle disease?

Newcastle disease is a highly contagious viral disease of domestic birds (including poultry) and wild birds. There are several different strains and, in its acute form, Newcastle disease has a very high mortality rate.

Can it affect all bird species?

Yes. Bird species most susceptible include chickens, turkey, emus, pigeons, pheasants, quail and guinea fowl. Ducks and geese are not as susceptible but may still be carriers of the disease even if they do not show any of the clinical signs.

What does Newcastle disease look like?

There are several forms of the disease.

Birds with a mild form of Newcastle disease may show no clinical signs or there may be some breathing problems and/or a decline in egg production with soft, misshapen or abnormally pigmented eggs.

The clinical signs of virulent Newcastle disease may start with depression, breathing difficulties and/or a drop in egg production, but they may develop other signs such as nervous tremors, paralysis and green or blood-stained diarrhoea. Birds may become unable to use their legs or wings or hold their head up straight. In some cases, birds can die so quickly that the clinical signs do not show up.

The clinical signs of virulent Newcastle disease can look very similar to those of Avian Influenza. Indeed, even post mortem examination cannot always reliably distinguish between Newcastle disease and Avian Influenza. As a result, any diagnosis made on the clinical signs or by post mortem may need to be confirmed by laboratory tests.

Does it affect humans?

People handling infected birds are at some, albeit low, risk of mild and short term conjunctivitis or flu-like symptoms. People who have not come into close contact with infected birds are not at significant risk.

Where birds show the signs of Newcastle disease, they are destroyed and not used for human consumption. Any virus in birds that were not showing any clinical signs of the disease would, in any event, be completely destroyed by normal cooking.

Where is it?

Newcastle disease viruses are endemic in most countries, including Australia. The endemic strain in Australia is known as "V4", which is avirulent (ie mild). However, avirulent strains can mutate into virulent (ie severe and highly infectious) viruses - and this is thought to have caused the series of localised outbreaks of Newcastle disease in NSW and Victoria between 1998 and 2002. Those outbreaks of virulent Newcastle disease were successfully eradicated. The V4 strain remains endemic in Australia, so the potential for further virulent outbreaks of Australian-origin Newcastle disease remains.

How is it spread?

The most likely method is by direct contact with infected birds. Other sources of spread include:

Manure from infected birds
Exhaled breath from infected birds can infect other birds downwind
Contaminated feed, egg cartons, chicken crates and other equipment
People can carry the virus in clothing, on shoes or even in nasal passages
Contaminated water.

What is the response to an outbreak of Newcastle disease?

Movement controls would be put in place to help contain the spread of the disease. Infected or high risk birds would be quarantined and destroyed, followed by decontamination of the properties involved.

Are the mild strains of Newcastle disease a risk?

Yes. The series of outbreaks of virulent Newcastle disease on the Australian mainland during 1998 to 2002 were thought to have been caused by the mutation of a non-virulent strain that has been endemic in Australia for some time. In other words, those outbreaks were not the result of virus coming from overseas but instead were of Australian origin.

What can be done to prevent Newcastle disease?

Vaccination is a most important part of our defence against a repeat of the home-grown outbreaks we had on mainland Australia in 1998-2002. It is compulsory for growers with more than 1,000 birds to vaccinate against Newcastle disease. In most cases, there is little point in people with a few backyard chickens vaccinating their birds. Further information is available on vaccination against Newcastle disease in the Biosecurity Tasmania factsheet:
Newcastle Disease in Poultry - Important information for people with a few backyard chickens (PDF 413Kb);
Ensure that wild birds cannot access, and thereby potentially infect, your birds' water and feed supplies or come into close contact with your birds;
Do not feed food scraps to your birds. Food scraps may contain viable viruses;
Ensure new birds brought onto your property are from a reliable, ND free source;
Ensure nobody has access to your bird or feed sheds unless they are complying with your onfarm biosecurity requirements.