Early detection of avian influenza by farmers is vital for containing and eradicating the disease within a premises and limiting further spread, according to David Mercer from DARD Veterinary Service.

Mercer was speaking at an event organised by the Ulster Farmers’ Union and the British Poultry Council at Greenmount last Friday to raise awareness and understanding of the risk of avian influenza to the 3m laying birds and 13.5m broilers in NI.

He said that DARD would rather have an increase in the number of negatively diagnosed reports of bird flu rather than a positive case, notified late, and that has had the opportunity to spread.

According to Fraser Menzies from DARD, outbreaks classified as low pathogenic avian influenza (LPAI) can be difficult to detect as symptoms only affect the lungs and gut and can be subclinical. However, highly pathogenic avian influenza (HPAI) outbreaks have the ability to enter all systems in birds. Symptoms include high mortality rates, loss of appetite, diarrhoea, open mouth breathing and depression.

He said that these symptoms are similar to other diseases and are not specific to avian influenza, meaning prompt testing for the disease is essential. Menzies added that LPAI can go undetected for over three weeks in flocks, allowing the virus time to multiply and spread. The shortest time from infection to clinical signs of HPAI is three days.

Sources

Menzies said that the primary source of infection is from wild birds by indirect contact through infected faeces. One million migratory birds pass through Ireland each year. The virus is not an airborne disease, as commonly thought, and can survive for long periods in damp conditions.

High rates of mutations and swapping of genetic material with the influenza virus mean developing an effective vaccination would be extremely difficult. Instead a strict biosecurity procedure is essential.

Good practice includes separate footwear and overalls for each poultry house, a designated changing zone, thorough cleaning of boots before disinfecting, use of a visitor’s book, cleaning water pipes and tanks with hydrogen peroxide and locking doors of poultry houses and yard gates.

Outbreak

An outbreak of avian influenza has never occurred in NI. However, farmers were warned not to become complacent with detection and biosecurity, as costs quickly build up in an outbreak. Three outbreaks of avian influenza in Britain in the last 12 months cost the poultry industry £50m.

“In the USA this year, there was good detection of outbreaks but biosecurity was poor which hit the industry hard. It cost $3.3bn over 223 outbreaks of highly pathogenic avian influenza over a few months,” said Gordon Hickman from the Animal and Plant Health Agency (APHA).

Contingency

If the disease is confirmed on a holding, birds are valued and slaughtered quickly on the premises so the virus is no longer replicating. David Mercer from DARD said that compensation is based on the bird’s value at the time of slaughter and the farmer is not paid for dead or sick birds so it is in the farmer’s interests to report the disease before it spreads throughout the flock.

In an outbreak, a 3km protection zone and a wider 10km surveillance zone around the infected premises is set up. Movements of poultry and poultry products from farms are restricted but can still happen under licence.

“Protection zones will last for 21 days after preliminary cleansing and disinfecting by the department. Surveillance zones last for 30 days. The zones might not be perfect circles around the farm and can extend along roads,” Mercer said.

Trade

Gordon Hickman from APHA emphasised that an outbreak in NI would stop trade of poultry products from the UK to countries both inside and outside the EU.

The final phase of cleansing and disinfection of an infected holding is the responsibility of the owner, and it is not until three months after this that the UK can regain disease freedom status from the World Organisation of Animal Health (OIE).

He said that usually trade within the EU begins once the zones around the infected premises are lifted, and with most countries outside the EU once the UK regains OIE disease freedom status.

One issue that could delay final cleaning and disinfecting in NI is the disposal of infected litter. In Britain, it is piled for 42 days then incinerated. However, with no incinerator in NI, litter has to be spread on land after six weeks. David Mercer acknowledged that getting a location where local residents were content for spreading to happen could prove difficult.