Stemming the spread of bird flu

What measures are in place to reduce the transmission of avian influenza?
14 February 2023

Interview with 

Ian Brown, APHA


A free-range chicken on a farm


So far, sixty-five bird species in the UK have been confirmed with avian flu infection, and tens of thousands of birds have been reported dead - almost certainly an underestimate - and internationally the number is north of a billion. So what should we be doing to stem the spread? The focus is very much on farming. Will Tingle spoke to Head of Virology at the Animal and Plant Health Agency, Ian Brown…

Ian - The first primary thing is to consider that this is a disease of birds with a large impact on poultry. So the focus of course is to control the disease in poultry. So the first key thing is to work closely with keepers of birds to report suspicion of disease early. That means that then investigations and veterinary inquiries can be conducted, samples can be taken, and rapid testing done, which means we get early detection. The earlier you detect a case, the better chance you've got of mitigating its spread and its consequence for that flock. Second thing is, upon confirmation of a case of bird flu in a flock of birds that are domestic, then there's a whole raft of measures that are put in place that follow international guidelines. The farm is effectively locked down. It can't move birds, people, equipment off. The effective population is rapidly culled, so the remaining live birds, and the premises are thoroughly cleansed and disinfected. And then there's a fallow period before that farm can go back into business. In the premises around the location within three and 10 kilometers, we talk about control zones, so this is where there's enhanced surveillance and monitoring to ensure there hasn't been any further spread of infection from that infected premise.

Will - And there are flu vaccines that do exist for poultry and other birds. How effective are they at combating the spread of avian flu?

Ian - Vaccination works effectively when it's part of a larger control program. So if you vaccinate and do nothing else, you will likely still have a problem because vaccinated birds can still get exposed and infected to the virus and they can still shed the virus and pass it onto other birds. However, when it's used in conjunction with other control measures, it can successfully reduce infection. But considerations for vaccination are complicated. It's not a simple fix. You need the right vaccines. You need to be able to administer them on scale, need to be able to administer them relatively cheaply. And importantly, you need to monitor all of your birds that you've vaccinated on a very frequent basis because you need to be confident that wild type virus hasn't entered your vaccinated flock. When you vaccinate, of course, your ability to clinically look for sick birds is compromised because by definition the birds won't get sick. So that means you have to do active testing and monitoring, which still needs to be fully worked out at international scale, how that can be done in a way that gives confidence.

Will - Are there any things that can be done to prevent the spread in wild birds? Because they seem to be the problem. They seem to be the ones taking it from farm to farm.

Ian - The disease or infection will ultimately probably die out in wild birds at some point. We know that for some species of wild birds, this has high lethality and it can get into discrete populations with biodiversity impact. So it is important that we can reduce that source infection. We have to be realistic. There is little we can do to actually protect the wild birds themselves. They will go through natural cycles of epidemic and recovery. And this is about making sure that where we can, we apply best practice to reduce contact between poultry and wild birds. And that means more education, more awareness. But recognizing that in some poultry production systems around the world is easy to say, it's not easy to do.

Will - At an economic level. Are there safeguards in place to protect farmers who could potentially lose their entire livelihood, should their farm get infected with this avian flu?

Ian - Well of course the first important thing is that the farmer's vigilant and he knows his birth and any changes that signal early signs of disease, it's important that those producers report. Because the earlier they report, the earlier we can confirm disease and if we do confirm disease, then the faster the birds can be culled. And then of course there's a valuation at that point, which will lead to some compensation. Obviously if a farmer reports a problem late and this is a very devastating, fast spreading disease, then he could have lost his entire flock. So early reporting is really important. Making sure they've got stringent biosecurity practices, and education of anybody that comes onto the farm. So limiting visitors and making sure that the operatives on the farm are well trained and well versed in biosecurity practice, that they have a protocol and that it's followed. Sadly we've seen a number of cases where there are protocols but they're not being followed by staff, or the protocols are inadequate. So that biosecurity is a really, really important investment for the producer of birds.

Will - There's been many reports now of the flu slowly creeping into mammalian species. Do you think the protocols will now have to change because the disease is now in some mammal species?

Ian - This has been observed in many countries around the world, including the uk and it's a consequence obviously of extensive spreading of wild birds. So what is being done in the UK and indeed probably in many other countries is we have ramped up our surveillance. So we are now running an in real time program to track and understand this spread from wild birds into mammals. So from January this year, DEFRA and the involved administrations supported a program delivered by Animal Plant Health Agency to actively target mammals that we think have a higher probability of exposure and infection with the virus. Once we detect positive animals, we will then analyze that virus, dissect it, look at its genetics, and determine whether we believe there are changes in that virus that might change what we call the risk profile, both for mammals and potentially of course for humans. So what we're looking for is changes in the virus that might signal some form of adaptation. So at the moment, all of the cases we've detected in the UK, which is now 13 over the last 12 months or so in several species of mammal to date, and not all the data is complete. We've seen some changes. Yes, we've seen a consistent change in the virus when it switches from birds to mammals, but what we've not seen yet is evidence that the virus is transmitting from one mammal to another. So that is very important. So are these just isolated spillovers, which lead to what we call dead end infection, or could they go from one fox to another or one otter to another? Now we have no evidence of that yet. So to date we haven't got any evidence of that. But that's obviously why we're doing the surveillance.


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