There are steps that need to be taken if avian influenza (AI) is suspected, and also following confirmation that the virus is present. 草榴社区 Guardian takes a look at what these steps are.
Poultry keepers must report suspicion of avian influenza (AI) and, while this process will vary depending on whether the premises is in England, Wales or Scotland, it will generally involve communication with a duty vet at the Animal and Plant Health Agency (APHA).
Zoe Treharne, veterinary lead for the avian expert group at APHA, says if the duty vet cannot rule out AI over the phone, they will then give verbal movement restrictions, and will send a veterinary inspector to investigate.
It is worth noting that APHA personnel who come on farm must wear full personal protective equipment, including a respirator.
Examine
The veterinary inspector will examine the farm and birds; this will involve looking at paperwork such as the visitor book, and they may perform a postmortem examination. If they cannot rule out notifiable disease, they will send samples to APHA Weybridge for testing. Formal restrictions will also be served.
Restrictions mean that poultry keepers cannot legally move anything on or off the farm without a licence. APHA will place a surveillance and protection zone around the farm, with restrictions on poultry keepers in these zones.
The testing carried out on suspect AI cases is usually performed on oral and cloacal swabs from birds, says Ms Treharne.
In some cases, dead birds will be sent to APHA Weybridge for postmortem examination.
There are two types of tests carried out under UK law, PCR, and virus isolation. The results of PCR are available within 24-48 hours.
"Virus isolation results are available between two and six days after the test starts. The six-day viral isolation is the last test result received, and if all other tests are negative, disease is officially negated, and restrictions are lifted.
AI confirmed what next?
Once testing confirms the virus, APHA undertakes further investigations, and the process is started to cull the flock prior to cleaning and disinfection. Ms Treharne says the farm will be assigned an APHA case vet as the point of contact for APHA.
Further investigations will then be carried out for two purposes; to assess how the birds became infected and the potential for spread from the farm.
Ms Treharne says: To speed along this process, the farm should nominate a point of contact. This person should have good knowledge of the day-to-day running of the farm and, if the farm is part of a larger business, they need to understand the business model including linked premises. They should also be able to easily access the farm records.
Documents
Ms Treharne adds visitor books, production information, and standing operating procedures are all useful documents at this stage.
The farm visitor book will show who has been on the farm, and this is essential for showing who may have carried infection elsewhere.
APHA will contact everyone who has been on the farm to find where they may have carried infection to. If they have been on other poultry sites, these may need visiting to investigate risk of AI infection.
Production records can also be used by APHA to find when infection may have started, for example by showing a reduction in feed or water intake. Ms Treharne says if information is only written on a board each day, taking a picture can be a useful way to capture this information.
Standard operating procedures will detail biosecurity measures, such as boot dip use and how often they are changed. These can be useful to show to APHA as they will clearly outline the procedures that personnel on farm follow.
Culling
Following confirmation of the virus, all birds on farm will be culled to minimise the spread of AI. A valuation estimation visit is performed 24 hours before culling starts. This is a count of all the healthy birds on farm and gives the maximum compensation amount. Compensation is based on the number of healthy birds at the start of the cull.
Ms Treharne says: APHA will organise culling as soon as possible after disease confirmation. The method of culling varies depending on the species of bird, and the house set-up.
Culling is done using the most humane method, to reduce stress of the birds.
During culling an APHA welfare vet will be on site overseeing the process to ensure that the welfare of the birds is paramount. APHA will arrange disposal of the birds.
Cleaning, disinfection and restocking
Farms require two rounds of cleaning and disinfection before restocking can occur explains Ms Treharne.
The first round is organised and performed by APHA and then the farm handles the second round after the plan has been signed off by the APHA.
The APHA case vet will work with the farm to discuss the different options available.
Restocking decisions are discussed with the APHA case vet and agreed with the APHA on a case-by-case basis.
Protection and Surveillance Zones
Once the suspicion of AI has been reported two circles are drawn around the farm. Ms Treharne explains that the first is the 3km protection zone; the second is 10km surveillance zone.
Poultry premises in these zones, including smallholders, are under restrictions. Due to restrictions, premises in the zones need licences for certain movements of animals, poultry litter and slurry. The rules differ depending on if the premises is in a surveillance zone or a protection zone.
Within the zones, APHA performs surveillance. Most surveillance is of poultry within the protection zone, and this takes the form of a visit. In the surveillance zones APHA will visit random poultry premises, and they may contact some by phone.
The zones are removed when the surveillance has been completed with no further cases of highly pathogenic avian influenza.
Licencing
If a farm is under restrictions, then keepers need licences to allow people and items on and off farm. For instance, if feed is needed prior to culling, then a licence is needed for this. Ms Treharne says licences are issued by APHA and licencing needs will be discussed by the APHA case vet. Within protection and surveillance zones licences are also needed for certain movements.
There are two types of licences general and specific. General licenses cover certain routine movements if the keeper meets the licence conditions. For example, there is a licence that allows the movement of poultry carcases for disposal from premises in a protection zone. The person responsible for the movement can be the licensee.
If a general licence is not available, then farms need to apply for a specific licence. The person who does this is responsible for ensuring licencing conditions are met. In some cases, this will require an inspection by an official vet.
