All quiet on the bird flu front - will it stay that way this autumn?

However, one has to consider that maybe all these dead birds found with traces of H5N1 may not be uncommon. In past years lots of wild birds could be found dead at the end of the winter. They were not tested as much before 2005. So it's not surprising that there were no findings.

And of course it's not just wild birds that can spread the disease. There is great concern both in the EU and the USA about illegally imported meat and illegally imported birds. It has been pointed out that the spread of the disease has followed trade routes rather than bird migration routes. The poultry industry itself has transmitted the virus - by sending hatching eggs from Turkey to Nigeria for example.

Outbreaks continue to pop up in the Far East. Laos reported an outbreak in late July 2006, and Thailand, which culled thousands of commercial poultry only last year, has another outbreak now. Of greater immediate concern to the EU is the serious situation in Romania. According to a report released by the US Department of Agriculture, 15 avian influenza outbreaks occurred during the second wave of the virus in May. The disease has left many Romanian producers on the verge of bankruptcy. Almost one million birds were culled during May, compared to 421,000 birds culled during October to December last year.

Whilst countries on and around the Black Sea experience outbreaks of the disease, re-infection of migrating wildfowl remains a possibility, and also transmission of the disease to the EU this winter. That is why Germany is continuing its locking up policy in parts of the country with large stretches of open water and waterfowl.

The bad news is that H7 has also re-appeared in Holland, August 2006, and H5N1 in Germany 4.8.06.

Avian influenza has always been around. What's the fuss?

Birds that are the natural hosts of influenza viruses do not always suffer from the disease. Problems occur when the virus spreads to intensively reared domestic poultry. Strains of H5 and H7 have the potential to mutate to highly pathogenic forms after transmission and adaptation to their new hosts. This situation is different from that in wild birds, where the birth of highly pathogenic forms had never been observed (Webster 1998).

Until the emergence of Asian lineage H5N1 viruses, wild bird populations were affected only sporadically, were locally restricted, and die-offs were virtually unknown. The problem in recent years has been the massive interface between poultry production and wild birds in S E Asia. In Thailand, Indonesia and Vietnam, poultry production has soared eightfold in 30 years, to 2.4m tons of meat in 2001. China, too, has seen poultry production rise, trebling to nine million tons a year, with most growth accounted for by new intensive farms. There have therefore been numerous opportunities for HPAI virus transmission to take place from infected poultry back to the wild bird population.

There has been a fundamental change in the behaviour of the disease since early 2005 when die-offs in wildfowl were reported. It was at first even questioned if these die-offs were avian influenza, since this had not been typical of the disease in the past. However, from these infections in the Far East, the disease has progressed towards Europe, resulting in the incidences of infection of wild birds in the EU. The die-offs around Lake Qinghai have been repeated in 2006.

' One may even come to look at the highly pathogenic forms as something artificial, made possible only as result of man-made interference with a naturally balanced system.' That is a statement from Lutz Gurter and Timm Harder of the Friedfrich Loeffler Institutute in Germany. If so this is true, then not only are the wild birds the victims of the systems we have put in place. All birds culled - the live burials, the live burnings and the inadequate methods of gassing - are a consequence of our actions too. This is no 'natural disaster'.

Will vaccination be compulsory?

Surely nobody has said that vaccination should be compulsory? Were this to happen, we would already be in a pretty desperate situation where ring vaccination might be used to stop the spread of the disease.This emergency measure does not preserve pure breeds and rare breeds. Since the vaccines take at least three weeks to be fully effective, ring vaccination creates only a limited buffer zone to give the culling teams time to do their job within the ring, and it is quite likely that infected birds would have been vaccinated. That would create all sorts of problems. Emergency vaccination is a situation best avoided. It is best to preventively vaccinate birds at risk, in high risk areas. In the future, perhaps commercial operations should also be subject to severe planning restrictions on their location. Why locate a new industrial unit in a high risk area? It should not happen with manufacturing - so why not with poultry units?

Can we breed for resistance to the disease?

For low pathogenic avian influenza, birds get mildly ill, and then get better. AI might not even be suspected at first; note that the affected farm in Holland had hundreds of dead chickens, but they attributed this to the hot weather. So they were just taken away in the normal way. So much for bio-security and prevention.

Also, the first free-range birds which contracted H7 in East Anglia in April showed few signs of illness. AI was not suspected at first. So birds can live and develop immunity to avian influenza. But LPAI can change from LPAI in outdoor birds and species to HPAI if it gets indoors to commercial chickens in conditions where there are several rapid cycles of infection. That's probably what happened in Holland in 2003. So LPAI should not be ignored whilst we have intensive poultry units. Many of us may not want these units, but they are a fact of life. If we could all go back to low density, organic systems, then the disease might be much less of a problem. But the industry now produces so much poultry meat that we have created a huge problem of potential mutation and transmission. Our food supply systems and over-consumption of animal protein are the fault.

It is very much doubted if outdoor poultry is any stronger. In commercial systems, these are usually the same breed as the indoor chickens but they experience part of their life outside. Organic and free range farmers like to think they have stronger chickens. The same goes for hobby birds. However, in view of the fact that even wild birds catch this H5N1 strain it is doubted that free-range birds are more resistant.

The density of industrial poultry is a much more important factor than strain of poultry. The stocking density of the birds and the rapidity of disease transmission does cause the mutation and explosion of bird flu.

"When low pathogenic avian influenza virus (LPAIV) strains are transmitted from avian reservoir hosts to highly susceptible poultry species such as chickens and turkeys (i.e., a transspecies transmission step!), only mild symptoms are induced in general. However, in cases where the poultry species supports several cycles of infection, these strains may undergo a series of mutation events resulting in adaptation to their new hosts. Influenza A viruses of the subtypes H5 and H7 not only run through a host adaptation phase but may have the capability to saltatorily switch by insertional mutations into a highly pathogenic form (highly pathogenic avian influenza viruses, HPAIV) inducing overwhelming systemic and rapidly fatal disease. Such HPAI viruses may arise unpredictably de novo in poultry infected with LPAI progenitors of H5 and H7 subtypes." http://www.influenzareport.com/ir/ai.htm So, perhaps we are caught between seeming to protect our poultry by keeping it biosecure inside, whilst creating conditions indoors which favour dangerous mutations, and causing huge problems in handling infected waste.

Do they vaccinate day old chicks?

There have been some pretty eye-catching adverts in the poultry press of day-old chicks about to be vaccinated by whole batteries of needles. Advertising licence? I think so.

At the moment, it makes no sense to the industry to vaccinate broiler chicks which have a life span of only six weeks. It would take at least half their life time to gain full immunity!

Longer-lived birds, such as pullets for laying, might be vaccinated in the future. The combination Newcastle Disease/ H5N1 droplet vaccine being developed in Germany (in conjunction with Intervet) may become a commercial reality in a year or two, but it could be five years away.

If vaccines delivered by injection were currently to be used for free range layers, as they are in Holland, then young birds (not chicks, but 7 weeks old) are vaccinated before they are released. A combination H5/H7 vaccine is produced by Intervet and DEFRA now has the option to buy 10 million doses.

Pure breeds are also being vaccinated in the Netherlands, as an alternative to shutting up the birds this September. The young birds are also vaccinated at around seven weeks of age. So, although there is this window where the birds are not protected from the virus it is at the least risky time of year, when the birds can also be reared partially indoors. Also, the chicks have protection from vaccinated parents for a few weeks. The vaccine is fully effective for the more risky cooler months. Goose breeders in particular have been interested in using the vaccine and Andrea Heesters reports no problems in using the vaccine on her birds. This is why the cooler months are more risky: "Avian influenza viruses reveal an astonishing capability to retain infectivity in the environment and particularly in surface water in spite of their seemingly delicate morphology (Stallknecht 1990a+b, Lu 2003). Virus suspensions in water have been shown to retain infectivity for more than 100 days at 17C. Below -50C the virus can be stored indefinitely. Data provided by Ito et al. (1995) and Okazaki et al. (2000) provided evidence that in the palearctic regions, avian influenza viruses are preserved in frozen lake water during the winter in the absence of their migrating natural hosts. Upon return for breeding purposes during the subsequent season, returning birds or their (susceptible) offspring are re-infected with viruses released by chance from melting environmental water. Along these lines, it has been hypothesised that influenza viruses can be preserved in environmental ice for prolonged time periods (Smith 2004), and that ancient viruses and genotypes might be recycled from this reservoir (Rogers 2004)."

Why are there so many different views on the use of vaccination?

Why are there so many political parties and religions? People never completely agree! Over the issue of vaccination and AI there will of course be different attitudes, different interests and different perspectives.

People who normally keep their birds indoors can only see disadvantages in vaccination. They feel that their birds can be protected by good biosecurity. However, note that the LPAI in Holland August 2006 was found in a closed system farm. Incidences of avian influenza show, time and time again, that biosecurity can be broken.

Where broiler meat is produced, or battery eggs, then the market could also be affected by consumer resistance to, as they see it, 'vaccinated' products. Many consumers do not know that chicken is being routinely vaccinated for various diseases such as Newcastle disease, gumboro, Mareks, salmonella etc, depending on where it was reared. Cooked chicken has also been imported from Thailand, which has experienced H5N1 avian flu, and Thailand has a current outbreak. How many consumers know this? How on earth can one tell what has happened in the life a cheap imported chicken? After all, EU rules stipulate that vaccination should be no barrier to trade in EU products.

Despite that regulation, vaccination of commercial poultry might limit sales. That is why commercial producers will shy away from vaccination; they do not want to limit foreign sales. As well as increasing their costs, vaccination will limit their market. Of course if vaccination of commercial poultry were to take place in several countries in the EU - then what would be the problem in the EU market, where most of our trade takes place?

Where birds are normally kept outdoors, then of course attitudes to vaccination are different. For people more concerned with welfare, free range and organic systems, then the option to vaccinate must be available. Which do you put first? Farming systems which are sustainable, with good welfare practice? Or mass production in systems which produce the cheapest product for the populace of the urban market which, on the whole, does not care about poultry welfare because they never see the issues? Which do you personally want to buy? A broiler which at seven weeks was not able to walk? Or a free-range organic bird allowed 12-13 weeks before despatch?

H5N1 has of course arrived in Europe when the methods of intensive poultry production are very much in question. The threat should not be allowed to disrupt sustainable farming systems and to favour factory farming, especially when the poultry industry is very much to blame for the circulation and re-circulation of the disease. A long term view is needed to combat this disease: a move away from the industrial security approach to lower stocking densities and sustainable systems. Our intensive poultry farming systems are all part of the problem of over-consumption and non-sustainable use of resources.

The view points of owners of pure breeds will vary too. Some will not want to vaccinate because their Belgian Bantams and Japanese can easily be kept in aviaries. That can be done with Call ducks, to limited extent, as well. But confinement is death to most waterfowl. Geese cannot be reared successfully, on welfare grounds or economic grounds, without grazing range. The veracity of that statement is illustrated by the situation in Germany. Between one third and one half of goose breeders in Germany have given up. Confinement has been enforced and, as a consequence, the birds have been culled. That is why some breeders want the option of vaccination should it become necessary. They certainly want the option in Germany now.

So a vaccination plan needs to be drawn up to accommodate many of these points of view. It is a very complex problem. After all, Dr Bernard Vallat (The Director General, OIE) wrote to Paula Polman of the NBvH, in answer to her query, that, 'Preventive vaccination should preferably be based on risk assessment to determine the right policy and the product to be used. Zoo animals, pets and poultry that cannot be confined have to be considered within this risk assessment.'