The 2 different types of IBDV
Infectious bursal disease virus (IBDV) can have a major impact on animal welfare, international trade, and the poultry industry economy.
It is a highly infectious disease of young chickens caused by a virus that specifically attacks part of the immune system. The outcome of infection depends on the age of the bird and the type of strain.
There are 2 different types of IBDV – Types 1 and 2. There are no known cases of IBDV type 1 (IBDV-1) in New Zealand commercial poultry, although the disease has been detected here twice before. Both times it was eradicated.
Type 2 is already in New Zealand and causes no significant health issues in the national flock and poses no trade concern.
Most chickens are susceptible from 3 to 6 weeks of age.
Younger birds that recover from infection can be permanently immunosuppressed due to the damage to the bursal lymphoid tissue, impacting production, and impairing the efficacy of subsequent vaccinations for other diseases.
IBDV types of varying virulence are present in commercial flocks around the world. The virus does not pose a food safety issue. Chicken meat and eggs are safe to eat.
Global distribution of IBDV-1
The virus is widely distributed throughout the world. Numerous detections have been made in Europe, the Americas, Africa, Asia, and in most countries which have an intensive poultry industry.
Why it is a problem for New Zealand
An incursion of IBDV-1 would have a major impact on our poultry sector, on market values, and possibly on our food security.
History of IBDV-1 in New Zealand
IBDV-1 was first discovered in New Zealand in 1993 and subsequently eradicated following an industry-led programme.
In 2019, IBDV-1 was again detected in layer hens at a South Island egg farm. Presence of the disease was picked up by a poultry producer through regular voluntary testing and confirmed by further testing at MPI.
Impacted farms were placed under biosecurity controls to prevent virus spread, and Biosecurity New Zealand undertook testing and sampling and worked with the egg and poultry industries to eradicate the disease.
Trade of poultry products to a few markets was affected, and the export of chicken meat to Australia was temporarily suspended.
In November 2021, the response was closed following a final round of testing that confirmed the disease had been eradicated from the affected properties and that New Zealand commercial poultry was again free from IBDV-1.
What we are doing
The ongoing industry-led 'Country Freedom Quality Plan' for IBDV in conjunction with MPI’s general surveillance programme ensures early detection of IBDV and provides ongoing confidence that the disease is absent from commercial chicken flocks in New Zealand.
If the presence of IBDV-1, or another exotic disease, is suspected, MPI must be notified.
How it could get here
IBDV is very hardy and can survive in a wide variety of environmental conditions. Meat from young chickens could contain the virus, which is very stable in tissues, and so existing regulations restrict meat importations to cooked products from approved sources.
Border controls enable us to intercept unauthorised or potentially contaminated items. Introduction of IBDV-1 into a young broiler flock by people who have been exposed to the virus while overseas visiting a poultry farm, represents one of the highest risks.
Accidental introduction by contaminated materials or the illegal importation of infected carcasses is unlikely but possible.
How to identify IBDV-1
Outbreaks of IBDV-1 are caused by virulent strains of the virus. Clinical signs are seen only in young birds and include:
- diarrhoea
- anorexia
- prostration.
Very young birds die suddenly. Mild strains of the virus do not produce clinical signs unless it's complicated by secondary infection.
Who to contact
If you suspect this disease in poultry, call the exotic pest and disease hotline 0800 80 99 66
