Newcastle Disease and backyard or smallholder chicken flocks

Introduction

From 1998 to 2002, mainland Australia experienced a series of outbreaks of virulent Newcastle disease. This resulted in the deaths of a very large number of poultry and the disease was eventually eradicated through a program of slaughtering chickens and ducks throughout the districts affected. It was a distressing time for everyone involved.

The poultry industry and all Australian governments have developed the Newcastle Disease Management Strategy to try and ensure that such outbreaks do not occur again. An important part of that Strategy is the compulsory vaccination of all commercial poultry flocks against Newcastle disease.

If you own a few birds, the following information may help you understand the situation.

What is Newcastle disease?

It’s a highly contagious viral disease that can affect all bird species. Virulent strains of the disease cause very high mortality rates among poultry.

What does Newcastle disease look like?

In some cases, birds can die so quickly that the clinical signs don’t have time to develop. But, if the signs do develop, they generally start with breathing difficulties and are followed by nervous tremors and then by the birds being unable to use their legs or wings. It is often difficult to tell the difference between Newcastle disease and Avian Influenza by the clinical signs. If any of your birds looks sick, you should always get it checked by a vet.

Are all poultry owners required to vaccinate against Newcastle disease?

No. If you have less than 1,000 birds, you do not have to vaccinate.

But, if I don’t vaccinate, won’t that mean my birds are a weak link in our defence against Newcastle disease?

No. A very mild form of Newcastle disease virus is present in all States. Providing that strain does not mutate into something virulent, it poses no threat to birds. The outbreaks we had on the mainland between 1998 and 2002 were caused by a mutation of the endemic mild strain (known as the V4 virus) into a virulent strain of the virus.

All the available evidence indicates that, for such a mutation to occur, it needs a large number of birds in a small area to “generate” the virus mutation process. In simple terms, a small number of birds cannot generate enough virus for the mutation process to occur .

Can I vaccinate my birds anyway, even though I won’t be required to do so?

Yes, but in almost all cases it won't be worth your while. The aim of compulsory vaccination of commercial flocks is to prevent the development of a virulent virus, not to protect individual birds.

Will vaccination protect my birds from Newcastle disease?

The primary purpose of the compulsory vaccination of all commercial poultry flocks is to try to prevent the endemic V4 virus mutating into a virulent strain that would cause major health problems, including high mortalities, in poultry. If an outbreak of virulent Newcastle disease does occur due to the introduction of a virulent overseas strain of virus, there will be a disease control campaign to eradicate the virus. Such a campaign would probably involve the humane slaughter of poultry in and around the infected property – including birds that have been vaccinated. Vaccination is no guarantee against slaughter in the event of an outbreak.

If I want to vaccinate my backyard poultry anyway, how do I go about it?

Biosecurity Tasmania now has a permit system to enable poultry owners to buy vaccine direct from the manufacturer. However, the minimum quantity available from manufacturers is currently 1,000 doses and we are not aware of any plans by manufacturers to produce in smaller quantities. If you have several hundred birds, the permit system may be worthwhile for you. For a small number of birds it may be better to discuss with your local vet the possibility of organising a group vaccination.

Is Newcastle disease a risk to human health?

Unlike Avian Influenza, it is not a significant threat to human health. People handling infected birds without proper protection are at some risk of getting short term conjunctivitis.