Animal Health Australia (AHA) coordinates the National Newcastle Disease Management Plan on behalf of its relevant stakeholders.
Newcastle disease (ND) is a viral disease of domestic poultry and wild birds characterised by gastrointestinal, respiratory and nervous signs.
The virus strains that cause ND can be categorised into three different types, based on their virulence (degree of harm) in chickens:
- velogenic (highly virulent; cause severe disease; often fatal disease)
- mesogenic (intermediate; cause coughing, reduced egg quality and production losses; some fatalities)
- lentogenic (avirulent or non-pathogenic; cause subclinical infection or mild respiratory symptoms; negligible fatalities).
Most ND strains are either velogenic or lentogenic; some are mesogenic.
While the epidemiology of ND is not completely understood, it is thought that wild birds, in particular water fowl, may be the reservoir for lentogenic strains of ND virus. These viruses could become more virulent after establishing in poultry.
The World Organisation for Animal Health (OIE) disease card on Newcastle disease provides detailed information on the worldwide distribution and importance of ND, including its aetiology (classification of the causative agent), epidemiology (host species, clinical and pathological signs and modes of transmission), diagnosis, control and public health relevance.
Australia’s Newcastle disease status
Australia is free from virulent ND, but this has not always been the case.
Australia’s first cases of virulent ND occurred in 1930 and 1932; both were eradicated according to a slaughter-out policy.
In 1966, an avirulent ND strain was identified. Evidence suggests that this strain and other avirulent strains have since spread through the poultry industry in all states.
During the 1990s, strains emerged that were associated with mild disease, and some were found to be genetically similar to virulent ND viruses.
In September 1998, a virulent ND virus emerged on a mixed layer and broiler farm at Deans Park, Western Sydney, New South Wales (NSW). Genetic sequencing showed that this virus had originated from an avirulent ND virus of Australian origin. It was genetically different from ND viruses that occur in other countries.
In April 1999, another outbreak of ND occurred at Mangrove Mountain on the NSW Central Coast.
In early 2000, cases of ND occurred in western Sydney and in Tamworth, NSW. After depopulating the Tamworth property, a national survey undertaken to help define the distribution and types of ND viruses circulating in Australia before taking response action on the western Sydney properties.
The national survey for ND virus distribution completed in late 2000 was designed to ensure coverage of all sectors of the Australian commercial poultry industry. The survey did not detect any isolates of virulent ND virus or any isolates with gene sequences related to the NSW virus outbreaks; all viruses detected were avirulent strains genetically distinct from virulent ND virus.
In early 2001, the birds on five remaining properties in western Sydney from which virulent ND virus had been isolated were destroyed.
In October 2001, Australia met international standards for freedom from virulent ND virus.
An incident of virulent ND was confirmed in mid-2002 on a single property at Meredith, Victoria, and another in late 2002 on a property at Horsley Park, NSW. In both instances, disease eradication processes prescribed in Australia’s AUSVETPLAN disease strategy for the control and eradication of ND were applied.
National response to Newcastle disease
Ratification of the Emergency Animal Disease Response Agreement in March 2002 heralded the first time that the private sector was involved in the decision-making process during the response to the Victorian outbreak in mid-2002.
The Agreement provides for industry representation on the biosecurity incident National Management Group (NMG), a high-level committee responsible for approving emergency animal disease (EAD) response plans and all expenditure relating to the response and recovery from an EAD outbreak.
The Agreement also provides for industry representation on the Consultative Committee on Emergency Animal Diseases (CCEAD), the committee of technical experts advising NMG on responses to EAD outbreaks.
An NMG meeting in May 2002 requested that AHA coordinate an immediate review of Australia’s policy for the management of ND, including topics such as active monitoring and surveillance and compulsory vaccination in designated risk areas. The review was conducted using an expert working group and a national workshop of key stakeholders to develop and agree on the technical and policy issues relating to a national integrated management plan.
Previous national Newcastle disease management plans
The National Newcastle Disease Management Plan 2002-04 was developed and the National Newcastle Disease Steering Committee (NDSC) formed. The plan followed a risk management approach, addressing goals for the long-term control of ND, as agreed by industry and government stakeholders. The objectives were to:
- minimise the risk of ND outbreaks from virulent viruses of Australian origin
- protect the status of non-infected flocks and regions
- reduce the social, economic and trade impacts of ND at farm, regional and national levels.
The NDSC and Australia’s Animal Health Committee endorsed an updated ND management plan for 2005–07 that confirmed the need for a national approach to management of ND to reduce the risk that circulating precursor ND viruses mutate into virulent forms, which would result in clinical disease. Vaccination of high-risk areas was a key component of the 2005–07 plan, and a set of vaccination standard operating procedures (SOPs) was prepared.
The ND management plan for 2008–12 was based on, and consistent with, earlier plans, and its goal remained to reduce the spread of precursor viruses through the application of poultry industry biosecurity plans and the strategic application and monitoring of vaccination using live V4 and inactivated vaccine. This plan included several new elements designed to reduce the amount of vaccination required by the vaccination SOPs.
The NDSC’s National Newcastle Disease Management Plan 2013–2016 kept the goal of a vaccination program that mitigated the risk of an outbreak of Australian-origin ND (AoND). There have been no outbreaks of AoND since compulsory vaccination commenced under the first plan. The 2013–2016 plan was a continuation of the 2008–2012 version, consistent with previous modifications designed to reduce the amount of vaccination required by the vaccination SOPs.
Current Newcastle disease management plan
A new National Newcastle Disease Management Plan (2020) has been developed by the NDSC and endorsed by the Animal Health Committee. It describes Australia’s management of ND for the foreseeable future including the SOPs for vaccination. It is accompanied by a ND Surveillance Plan for unvaccinated broilers, for surveillance in any state where vaccination of broilers for ND is not compulsory, as permitted under the Management Plan (i.e. TAS, QLD, SA, WA).
Newcastle disease vaccination program
The vaccination program aims to displace precursor strains of ND virus that have sequences close to the virulent sequence and that might result in the emergence of virulent ND virus.
The ND Management Plan includes vaccination (according to the nationally agreed Newcastle disease vaccination program – SOPs of commercial domestic chickens in all states and territories. In jurisdictions considered to be of low risk for an outbreak of ND, vaccination of short-lived birds (i.e. birds of relatively low risk) may be reduced as per the revised SOPs. However, in flocks that opt for reduced vaccination, surveillance protocols as detailed in this plan must be implemented.