Opinion: A vet’s view on avian flu

By Alex Royden, BVSc MRes MSc PhD MRCVS, Poultry Health Services

Alex Royden is lead vet for the northwest practices of Poultry Health Services in Tarvin, Shrewsbury and Preston. She has been part of the team at PHS since 2018, before which she completed a PhD on the role and impact of biosecurity in the control of Campylobacter in commercial broiler production.

Avian influenza (AI) is a horrible disease, not just for the affected birds’ health and welfare, but also for the people involved too. It is stressful for the farmers who deal with the consequences of an outbreak, and it can take an emotional toll on the people who work with the birds, to see the animals they have reared go to waste. However, there are strategies which can help poultry businesses become as resilient as possible. Knowing the signs of disease and understanding what would happen in the event of a local outbreak can help businesses prepare, whilst implementing the tightest biosecurity measures, which will reduce risk.

AI is not an airborne disease, it is spread through contaminated material, such as faeces from wild birds coming into chicken sheds on workers’ boots, so it is worth reviewing the systems in place and whether any biosecurity measures can be improved.

Spotting the signs of AI can sometimes be challenging, however high pathogenic cases are easier to diagnose. Chickens, turkeys and other reared birds are all prey species, which means they often hide signs of illness until they are very sick or even close to death. This makes sudden death a sign of AI, but also a common sign of other diseases too. The visible signs of this disease can also be different between species. Respiratory symptoms such as gasping, panting or coughing, decreased feed intake, diarrhoea, swollen heads or blue discolouration of bird’s wattle and combs are all possible signs of AI, but could be caused by other diseases too.

With low pathogenic strains of the disease, the signs can be very subtle, sometimes simply a drop in egg production or slower growth. Therefore, asking your vet to investigate anything that is not quite right is the best way to be vigilant. The vet will conduct diagnostic tests to rule out other causes.

If the vet cannot rule out AI as the cause of disease, the potential case will need to be reported to Defra. The farmer can call to report the disease themselves, but vets are legally required to do so if they suspect AI. Whoever makes the call, they would initially speak to the APHA duty vet to talk through the case, who would then discuss it with their colleagues to determine the likelihood that it is AI and decide whether it is a report case.

For a report case, the farm would be placed under restrictions and a vet from the APHA would come out to the farm to take samples to test for AI. The exact restrictions are determined on a case-by-case basis, depending on the level of risk.

With AI, there is also a ‘test to exclude’ option available in certain circumstances. This is only for cases where the farmer and vet do not think that AI is present, but it cannot be ruled out, for example if there is another disease present but it does not fully account for all the symptoms the birds are showing. If going down this route, the vet would do the testing and the farm would not be placed under restrictions unless the tests came back positive.

As well as looking out for signs and understanding what would happen in the worst-case scenario of having an outbreak on-farm, it is also worth being prepared for the consequences of being placed in a protection or surveillance zone. Protection zones cover a 3km radius around an outbreak, while surveillance zones cover a 10km radius. There are strict rules regarding movement of chicken litter and manure, hatching and table eggs, chicks, pullets or birds for slaughter from any farms within these zones. The exact regulations differ depending on the type of animal, so it is worth understanding what it would mean for your business if you were to be placed within either zone, and what licenses you would need to apply for to be able to move eggs or birds from the farm. It can even be worth pre-filling in the application forms for any licenses that would be required, so all the information would be ready to submit the application as soon as it is needed.

Finally, it is imperative to note that with AI, doing the right thing does not just benefit one farm, or those in their local area, it protects the national flock.


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