Newcastle disease

ND is caused by Newcastle disease virus, which is an avian paramyxovirus type 1 (a virus in the family Paramyxoviridae).

Virus strains vary in severity:

• Velogenic (virulent): Causes severe disease and high mortality.
• Mesogenic: Causes moderate disease and mortality.
• Lentogenic (avirulent): Causes mild or no disease; often used for vaccines.

ND is a highly contagious viral disease that affects domestic poultry (especially chickens), cage and aviary birds, and wild birds.

Worldwide

ND occurs in most countries.

Virulent ND is a major global poultry disease and can cause serious trade and production losses.

Australia

Virulent ND outbreaks have occurred in Victoria and New South Wales.

ND prevention is now managed under the National Newcastle disease management plan (NNDMP), supported by vaccination in commercial chickens.

Queensland

Queensland is considered low risk for virulent ND.

ND vaccination is compulsory for layer chickens in Queensland.

In low-risk states (including Queensland), some short-lived flocks, such as broilers, may have reduced vaccination requirements but must still be included in ND surveillance.

All bird species are susceptible:

• Chickens are the most severely affected, particularly by virulent strains.
• Turkeys and game birds can also be seriously impacted.
• Cage and aviary birds show varying severity depending on species and virus strain.
• Wild birds often have mild or no symptoms but can still spread the virus.

In birds:

• Infection typically occurs through contact with infected birds or contaminated materials.
• Virus spreads in the respiratory, digestive, and nervous systems.
• Infected birds shed the virus in droppings and respiratory secretions.
• Incubation usually lasts 5–6 days.
• Virulent strains can cause rapid illness and high mortality.

In the environment:

• Virus contaminates litter, dust, sheds, equipment, feed and water.
• It survives longest in cool, moist conditions and organic material such as manure.
• Survival is shorter in hot, dry, sunny conditions.

Viscerotropic velogenic ND (severe intestinal form)

• Death within 2 days (survivors may develop twisted necks and muscle twitching)
• Mortality rate up to 90%
• Sudden, rapid onset
• Severe depression
• Loss of appetite
• Sharp drop in egg production
• Laboured breathing
• Swollen head
• Blue comb
• Green diarrhea
• Dehydration
• Collapse

Neurotropic velogenic ND (severe nervous and respiratory form)

• Mortality rate of 10–20% (higher in young birds)
• Severe coughing
• Severe gasping
• Head tremors
• Paralysis of wings and legs
• Twisted necks
• Depression
• Loss of appetite
• Reduced egg production

Mesogenic ND (moderate form)

• Mortality rate of 10%
• Coughing
• Sneezing
• Nasal discharge
• Depression
• Weight loss
• Reduced egg production (for up to 3 weeks)

Lentogenic ND (mild form)

• Rare deaths
• No visible signs
• Some birds may show mild respiratory symptoms, loss of appetite, or reduced egg production.

Differential diagnoses

• Avian influenza
• Avian paramyxovirus
• Infectious bronchitis
• Infectious laryngotracheitis
• Other viral, bacterial and parasitic gut and respiratory diseases

Laboratory testing is required to confirm ND and identify the virus strain.

ND can cause:

• rapid, severe disease with high mortality
• human destruction of flocks
• reduced egg and meat production
• costs for culling, disposal, cleaning, disinfection, vaccination and surveillance
• movement restrictions on birds, eggs and products
• loss or suspension of export markets
• long-term effects on Australia’s poultry health status.

The disease can have significant emotional and financial impacts on poultry owners.

Environmental

ND virus enters the environment in faeces and respiratory secretions from infected birds.

It can be transmitted by:

• moving live birds, even if they appear healthy
• contaminated cages, equipment, vehicles, and egg trays
• clothing, boots, and the hands of people moving between sheds or farms
• poorly cleaned catching and transport equipment
• dust and aerosols by moving between sheds.

Birds

ND virus is usually spread by:

• direct contact with infected birds
• virus shed in faeces, nasal and eye discharges, or respiratory droplets
• contaminated feed, water, litter or surfaces
• close contact in sheds, cages, shows and markets.

Humans

ND virus is zoonotic, meaning it can infect humans. Human infection is rare.

People are exposed mainly by:

• handling sick or dead birds
• contact with contaminated faeces, litter or equipment.

In people, infection usually causes only mild, short-term conjunctivitis. Anyone who develops eye symptoms or flu-like illness after exposure should seek medical advice.

There is risk of infection throughout the year.

Outbreaks are more likely when:

• flocks are unvaccinated, or vaccination is incomplete
• birds from different sources are mixed (for example, shows, markets, multi-age sites)
• biosecurity, hygiene or pest control is poor
• new birds are introduced without quarantine or health checks
• manure, litter or dead birds are poorly managed.

ND has an incubation period of 2–15 days. Moving apparently healthy birds can spread ND to new areas.

If you suspect ND:

• Isolate sick birds.
• Stop the movement of birds, eggs, and equipment on and off the property.
• Prevent contact between your birds and other flocks.
• Do not send birds to sales, shows or slaughter until advised.
• Contact your veterinarian to arrange examination and testing.

Legal obligations

If you become aware of or suspect clinical ND in any animal, you must report this as soon as practicable to:

• Biosecurity Queensland on 13 25 23
• or
• the Emergency Animal Disease Hotline on 1800 675 888.

If you own, treat or manage birds, you have a general biosecurity obligation to take all reasonable and practical measures to prevent or minimise the effects of biosecurity risks such as ND. This means you are legally required to reduce the risk of ND and limit its spread when dealing with possible carriers.

This includes following vaccination, biosecurity and reporting requirements, and cooperating with the Newcastle Disease Surveillance Program.

Advice for bird and poultry owners

Monitor your birds for:

• sudden increases in illness or deaths
• drops in feed or water intake
• drops in egg production or egg quality
• breathing problems (coughing, gasping)
• green diarrhoea
• nervous signs (tremors, twisted necks, paralysis).

Consider ND as a possible cause if:

• several birds become sick or die over a short period
• birds have recently been moved onto the property
• birds have attended shows, sales or other gatherings
• wild birds have close access to sheds or feed.

Prevention

Following good biosecurity and management practices will help to prevent disease and restrict its spread.

Guidelines for prevention:

• Vaccinate commercial chickens as per the NNDMP.
• Keep sheds and equipment clean and dry.
• Dispose of litter, manure and dead birds regularly and appropriately.
• Bird-proof sheds and feed stores to prevent wild bird entry.
• Limit visitors and require clean clothing and footwear.
• Clean and disinfect all equipment, crates, and vehicles between farms and flocks.
• Buy birds from reputable suppliers with known health and vaccination status.
• Quarantine and monitor new birds before adding them to your flock.
• Do not mix birds from different sources at shows or on your property.

Backyard and small-scale poultry owners should discuss ND vaccination and biosecurity with their veterinarian or poultry advisor.

Outbreaks

If virulent ND is suspected or confirmed:

• Restrict movement and quarantine infected or at-risk flocks.
• Humanely destroy (stamp out) infected flocks.
• Vaccinate at-risk flocks if needed.
• Clean and disinfect premises, equipment, and vehicles.
• Trace potentially exposed birds, products, and equipment.

The Newcastle disease surveillance program, authorised by the Biosecurity Act 2014, will conduct surveillance to ensure eradication.

Movement restrictions

If virulent ND is detected:

• Movement restrictions will apply to all affected and at-risk properties.
• Strictly control or prohibit the movement of birds, eggs, manure, litter, feed, and equipment.
• Restrict the slaughter, sale, and export of birds and products from quarantined areas.
• Maintain quarantine until cleaning, disinfection, and surveillance confirm the virus is eliminated.

Intensive surveillance activities will confirm the virus has been eliminated.

Vaccination

Vaccination against ND is mandatory for all commercial layer chicken flocks under the NNDMP.

Short-lived flocks (commercial broilers) may have reduced vaccination requirements, but it is recommended to participate in the Newcastle disease surveillance plan for unvaccinated broilers (PDF, 468KB) under the NNDMP.

Vaccination:

• reduces the risk and impact of ND
• does not completely prevent infection or virus shedding
• must be combined with good biosecurity.

For detailed vaccination information, see information for veterinarians.