US poultry producers have experienced serious disease outbreaks. What can UK producers learn from their experience?
Poultry producers on both sides of the Atlantic need to prepare for the worst as autumn approaches and the threat of avian influenza returns.
Cobb animal health director Kate Barger says that the outbreak that hit the US in 2015 wiped out 23% of the country’s layer flock and 7% of its turkeys.
Total economic costs were put at $3.3bn, including the value of lost layers ($1bn), lost turkeys ($530m) and the costs of culling and disposal ($500m). Consumers were also paying more for eggs, while long-term jobs had been lost to the industry and some key export markets were closed.
That was despite all states having rigorous AI plans and testing regimes in place before the disease struck. “We thought we were prepared for the waves,” she said. “What we were not prepared for was the tsunami. We could not deplete flocks fast enough.”
Field observations from the US
- Onset of disease from exposure to symptoms – 7-11 days
- Older birds – 12 weeks-plus – were the most susceptible
- Depression would set in before mortality
- Initially, mortality was often seen in pockets of birds within the whole flock
- Once established, mortality from AI could reach 80% within four days
Furthermore, the worst could be yet to come, Dr Barger told the meeting.
So far this year, highly pathogenic avian influenza had appeared in the Pacific flyway, the Central flyway and the Mississippi flyway. “The Atlantic flyway, which has some of the biggest poultry concentrations in the US, was spared,” she said. “We got lucky.”
But John Clifford, chief vet at the USDA, had recently predicted that HPAI would be in all four flyways this autumn. The US government was preparing for 500 cases – double the number seen in the spring.
“If it takes hold in the Atlantic flyway, it will be devastating,” said Dr Barger. But she also warned that producers in the UK should be wary, too. “You all share a flyway with the Atlantic. You also share flyways with Continental Europe, which dips down into Africa and the Middle East where they already have influenza cases.”
Learning from the US
There were many key learnings from the US experience, said Dr Barger, though two stood out.
The first was the fact that the virus showed an alarming ability to persist in the environment. The second was that US biosecurity had not been good enough.
“You’ve got to have good biosecurity, and you’ve got to depopulate affected flocks extremely fast in order to reduce the viral load in the environment and reduce viral shedding.”
Research showed that virus survival was better in lower temperatures than during the summer. “Winter weather is coming, the birds are going to start migrating and we know that that virus can survive in faeces as well as in water for much longer, so the risk is starting again.”
Modelling of the affected farms also showed that farms located downwind of an infected premises were four times more likely to become AI-positive.
This was because the virus could ride in the dust, feathers, litter and crop debris from infected farms. As a result, the advice in the US had been to avoid moving anything off infected farms, including the dead birds. Instead, everything should be composted on farm, to reduce the chance of feathers and dust reaching other poultry sites in the area.
With AI now an ever-present threat, poultry producers and companies should evaluate the risk factors and plan ahead, said Dr Barger. “Being prepared means prevention, early detection and depopulation.”
The presence of nearby standing water, or harvested cereal crops, would increase the risk from wild birds. The proximity of other poultry farms was another factor, as was the incidence of shared equipment.
As for specific measures, Dr Barger highlighted the following:
- Disinfect everything that comes on to the farm
- Disinfect on a hard surface – this is far more effective than doing it on gravel or dirt
- Use high pressure to clean vehicles, and use a disinfectant with anti-virus properties
- Maintain and use foot-dips and hand sanitisers properly
- Provide different boots for each shed, and use barriers
- Seal buildings and avoid all contact with other birds
- Limit multi-farm access during high risk periods for service technicians and farm staff
- Make drivers and farm visitors change clothing, using a colour-coding system
- Have shed-specific tool kits
- Trees can provide a natural barrier, reducing dust or feathers reaching the farm
- Only use a dedicated rodent controller, who does not go to multiple farms
- Keep grass cut short, eliminate rubbish and clear up feed spillages
- Remove dead birds at the end of the day, and do not then return to the shed
- Lock gates and secure buildings
- Ban personal items such as mobile phones and keys from sheds
- Make sure this is all executed every single day