By Stephen Lister, poultry vet
Some 74 infected premises and nearly two million birds lost already – not the headline we wanted to see. Although we were predicting that this winter would present a challenge from Avian Influenza (AI) I don’t think any of us expected the scale and number of outbreaks we have experienced over the last month.
Also, we were not quite expecting the H5N1 strain to be involved in the outbreaks rather than the H5N8 that caused the disease outbreaks in winter 2020/21.
So, what went wrong? We always expected that the virus would appear here through wild bird migration and would be the major source of any outbreaks in commercial and backyard flocks. It seems that the wild bird migration started earlier than in previous seasons and was in unprecedented numbers. This may reflect something happening in their summer habitat but all we really know is that these birds, mainly wigeon and teal, decided to migrate early and quickly, are all here now and appear to have led to widespread and heavy loading of the environment with faeces and carcases heavily contaminated with the H5N1 virus. That is bad news if that contamination is close to a poultry farm. These birds appear to have spread around the country with wild bird detections, and corresponding poultry outbreaks, across England, Wales, Scotland and Northern Ireland. There do appear to be some hotspots of commercial outbreaks in areas such as Yorkshire and Lincolnshire, reflecting the perfect storm of the types of migrating birds, their number, and where they have come to feed over winter in an area densely populated with poultry farms.
The pattern of cases led to the announcement of the compulsory regional Housing Order first in the Yorkshire hotspot on 21 November and then quickly across the whole of the UK on 29 November. Housing has been assessed in the past as important in reducing the number of expected infected premises, but this is not the sole procedure needed to prevent outbreaks.
Other investigations so far suggest that producers have mostly heeded the message to keep their farms as isolated as possible from any others so that spread between farms is less likely (although not impossible if we let our guard down). However, the key now is that the biosecure area for all producers must come down to each individual house on a site.
What is clear is that with so much environmental contamination, it is walking in of contaminated wild bird faeces or equipment or things contaminated with droppings that will introduce infection into individual poultry sheds.
With muddy farm tracks, potholes and puddles between houses, just depending on a quick dip into a footdip outside a shed, with anything other than fresh disinfectant at the recommended dilution rate is unlikely to stop you walking in the virus. The entrance to each shed should now become the fortress with a change in boots and other PPE before you enter the bird area in ANY shed, not just when you arrive on farm each morning. The same goes for equipment, pallets, straw bales, straw choppers and anything else that has to go into a shed. Even if they were stored undercover elsewhere on farm they will become contaminated as they are moved across a farm track or concrete roadway and can be virtually impossible to disinfect effectively so can easily carry in the very small amounts of virus capable of infecting a whole flock of birds.
This is not rocket science, but rather a back to basics approach and to think how small amounts of virus can get in contact with your birds, and prevent it. The virus will always exploit the weakest link and we have to break the link.
About half the cases detected so far have been in commercial flocks of differing sizes, with the rest being in backyard flocks, wildlife centres or other small collections of captive birds. The commercial flocks have been a mix of commercial layers (free range and colony), turkeys (seasonal, commercial and breeders), broiler breeders and a few duck flocks.
Epidemiological investigations are continuing into the pattern of the outbreaks, but most seem to be separate individual incursions, except for a few that are in very close proximity to each other.
Detecting an affected flock is not always easy although the mantra of ‘something out of the ordinary’ still applies. Anecdotal information coming from the affected flocks suggests that most of the turkeys, ducks and chickens seem to present with signs of sudden unexplained mortality, initially quite low but then escalating rapidly, with some nervous signs as head or body tremors or twisted necks reported.
In commercial layers there may initially just be a few dull birds, reduced feed intake and then some pockets of unexplained mortality around the house before any effect on egg production. The situation then quickly deteriorates with increasing mortality in most situations.
So, the message is clear, as previously warned – look for any unexpected behaviour or losses in your birds and seek advice quickly. Obviously, there can be other causes, but in the current climate, anything out of the ordinary should be reported to your vet or direct to APHA to allow a discussion or investigation to take place, whilst at the same time keeping your farm isolated. The key is, and always has been, that prompt detection allows prompt action and limiting the chances of spread.
The number of outbreaks in such a short timeline, each with their own control zones (PZ and SZ), is a major trauma to all involved and is a significant drain on resources in terms of manpower, patrols, catching, killing and disposal of infected flocks. The fallout in terms of restrictions on bird movements and the necessary issuing of licences to allow essential movements is also causing difficulties for producers. The procedures have to stay in place to limit possible spread of infection and infected flocks need to be killed out as quickly as possible to reduce the amount of virus present. APHA are working hard to fulfil all their obligations on disease control but they need help from the industry to keep doing the things we are doing well but plugging all gaps and closing any weak links to prevent new cases occurring. We also need to maintain accurate and easily accessible records of all performance data and bird/people/equipment movements on and off farms as these will aid APHA with their tracings and allow them to manage risk of spread.
These are unprecedented and difficult times for our industry, both in terms of the economic loss but also the welfare of our birds and producers. We must do everything to support each other and take time to consider your own mental health and all those working with you.
So, the messages remain clear:
- Think about what you are doing on your farm and between farms, where virus might be sitting on your site and how you might track it into your birds – farm biosecurity addressing weak links
- Prevent physically bringing virus coming into a shed – operate a fortress mentality
- Reset your biosecurity border – consider each poultry shed as your ‘biosecure area’ and make sure that any virus in the environment of your farm stays at the shed door and is not allowed to enter
- Procedures – change boots and other PPE between EACH SHED, make sure that anything that must go into the poultry shed is EFFECTIVELY cleaned and disinfected
- Create clear strategies and procedures for your farm and make sure ALL staff buy in to it – basic precautions done well and consistently
- Consider the health and welfare of your birds, your staff and yourself in these most difficult of times