It is always difficult timing an article like this – the situation can change rapidly making any advice obsolete!

Hopefully as this goes live the situation will be much as it is now – the immediate panic has worn off and we can make realistic plans for disease control. With so much media hype reality is often left behind. Hopefully I can answer some of the many questions that arise:

What is Bird Flu?

We are referring to a very large viral group known as Avian Influenza A which consists of 16 separate haemagglutinin (H) subtypes. “Highly Pathogenic Avian Influenza” (HPAI) viruses being specific to subtypes (H5 and H7) within this group. “Pathogenic” refers to their ability to cause disease – hence “highly pathogenic” means they are very likely to cause disease in many avian species. There are also “Low Pathogenic” AI viruses (LPAI) that may be hard to distinguish from the other strains without sophisticated diagnostic tests yet cause milder signs.

The viruses are further classified according to the antigens (H and N proteins) that they carry – hence the virus causing current concern is H5N1 strain. This not a unique virus – there will be many bearing this classification. However, this particular virus has been found spreading around the world from its origins in Asia and has caused much bird mortality in the last couple of years.
These influenza viruses are also referred to as “Influenza A”. This is the family of viruses to which they belong and they are closely related to mammalian Influenza A viruses.

Signs and Spread

Influenza viruses have been shown to infect a wide range of bird species though may cause slightly different clinical effects depending on species and a range of environmental factors. In raptors it will cause a respiratory infection (nasal discharge, tracheal inflammation, pneumonia, diarrhoea, nervous signs (fitting, etc) and death. In some cases death may occur before many of the major signs have started. The virus is excreted in respiratory discharges and faeces, so infected or carrier birds can easily pass on virus to naïve or susceptible birds or populations.

However, it must be remembered that this is principally a virus of the poultry industry. Here it is responsible for mass mortality and huge production losses. Most of the spread of virus in the current outbreaks can be attributed to movements of poultry around Asia. However, some spread is due to the migration of wild birds, especially waterfowl and these may be the main source of infection to captive raptors.

When designing measures to keep out migratory birds, consider that any contact may be dangerous. However, contact with the odd dropping is less likely to cause disease than close or prolonged contact with a sick bird. It is also apparent that wild birds live with avian influenza viruses most of the time. Many studies have shown them to be present in healthy birds and it appears that most live in a “balance” with the virus. The virus, however, keeps evolving and changing so wild bird mortalities will occur until the birds’ immune systems catch up.

If avian influenza virus is a fact of life with wild birds, why the fuss now? We have had outbreaks of HPAI infections in the UK from time-to-time, the last one in commercial birds in 1991/92, and these are usually rapidly brought under control.

However, we must remember that avian influenza A viruses are closely related to mammalian influenza A viruses. This current H5N1 strain has shown itself to be capable of infecting people (when in VERY close contact with infected birds) and there may have been one case of human to human spread, i.e. it has the potential to evolve just a little bit more and become a serious threat to human health.

So, while it is currently very much a bird disease, it has the potential to become worse and possibly cause a serious infection to the human population.

What Controls are currently in place?

At the moment imports of wild birds from outside the EU have been stopped.

Biosecurity in poultry movements have been stepped up.

These measures will, hopefully, prevent entry of virus to the UK, and identification of virus in a quarantine station showed (not only that quarantine set ups need improving!) but also that, basically, quarantine works.

However, we cannot stop migratory birds. While these are a small risk, they are a possible source of infection. The threat for this year may have gone due to the end of the winter migration, but will return next Autumn as birds return from Eastern Europe.

Within the UK there is control of meetings of birds. This may seem bizarre as we currently do not have the virus and the threat has receded, so it is hard to say when these controls will be lifted. However, any regulations to prevent this virus from entering and spreading in the UK would be beneficial.

Bizarrely too, there are no controls on a single falconer flying his bird at quarry – only if there are two or more falconers!

Nonetheless if you wish you want to organise a meet, the following must be done:

1. Apply to DEFRA for a license. To do this you must contact your local Animal Health Office for an application form. Full details of birds, location and purpose of the meet are required.
2. Obtain the services of a vet! The vet must be willing to take responsibility for the meet and must be available on that day to examine or treat any sick or injured raptors. It is also no use just listing a practice or clinic – it is the individual named vet who must be available. Whether they should be on site or just available so birds can be brought to them is unclear. Whatever, speak to the vet first and obtain permission to use their name. It is also useful if we can have a copy of the application and license for our records.

At the moment there is no requirement to bring all birds under cover and it is not advised to do this anyway – risk of significant contact with wild birds is small and risks of aspergillosis inside is, for many species, MUCH higher!

Above all, everyone is asked to:

1. Be vigilant. Watch out for large numbers of dead birds in any one place (especially waterfowl). While DEFRA are not interested in single dead birds they may get jumpy if a dozen or more are found. Do not pick up bodies – just contact the DEFRA Helpline (08459 335577). This is also a useful number for license queries, etc.
2. Practice biosecurity. This refers to the prevention of entry of viruses. It involves hygiene and disinfection as well as physical means of preventing viral entry. Advice on this can be found in some very useful leaflets from DEFRA (contact the local Animal Health Office), or from your vet.
3. If you have more than fifty birds then you must register with DEFRA.

What about Vaccination?

Vaccines against HPAI do exist. There are protocols for use in birds of prey and evidence to show they may be effective.

However, they cannot be used within the UK without specific permission from both the European Commission and DEFRA.

Why?

Basically, in an outbreak, birds within a certain distance of diseased premises may be blood tested for exposure to virus. Any found positive are likely to be culled. While there are means to distinguish between vaccinated birds and infected ones, it is unlikely that these tests will be able to be used quickly enough – the whole point of a test and cull policy is speed (hence some of the problems in the last Foot & Mouth Disease outbreak).

Similarly, vaccines do not prevent infection – while they may alleviate symptoms there is a risk that some vaccinated birds may carry and shed the virus both in their faeces and respiratory exudates, allowing susceptible birds to succumb to the disease.

Nonetheless it is likely in an outbreak that vaccine will be made available in certain cases.

The threat to captive raptors is small at present but may increase. If the virus enters the UK, various disease prevention measures may be enacted. The nature of these will depend on the source and degree of risk and, in such a situation you will be advised by DEFRA and your vet as to the best way of fulfilling these legal obligations. Above all, do not panic but listen to veterinary advice NOT the papers!

John Chitty BVetMed CertZooMed MRCVS

Thanks to Ruth Manvell of VLA Weybridge for help in writing this.
This article previously appeared in The Falconer magazine