Time to rule the roost

Outbreaks of the highly pathogenic avian influenza (HPAI) virus H5N1 have been reported in Hong Kong since 1997. The geographical location of Hong Kong strongly suggested that these outbreaks were part of a serious H5N1 problem in a much wider area in Asia, and in 2003 and 2004 new outbreaks of H5N1 were reported across Asia. While the virus was successfully contained in South Korea, Japan and Hong Kong, it continued to create problems in other countries such as China, Vietnam, Indonesia and surrounding countries. In 2005, the H5N1 virus spread from Asia to Mongolia, Kazakhstan and Russia and from there to, amongst others Turkey and Iraq.

Problems in surveillance, diagnostic capacity and transparency continue to exist and while the number of reported human fatalities is over 80, it remains unclear exactly how many people have been infected and how many of these have developed a clinical disease. In 2003 in The Netherlands, 50 percent of the poultry workers assisting in the eradication of H7N7 became infected and developed conjunctivitis. Furthermore, 60 percent of the family members of these people also became infected. This suggests that the number of people infected with AI might be much higher than is reported.

In spite of all efforts, the H5N1 virus has spread from Asia to Russia and from there to the Middle East. It is clear that a more aggressive approach is urgently required.

Achievements since 2003
Surveillance is the basis of any strategy to control or eradicate the virus. However surveillance alone does not control the virus; it only tells us where to apply the control program. Aggressive methods are necessary to contain the virus in the area and to control or eradicate it. The cornerstones are biosecurity (prevention of new cases) and culling or vaccination or a combination of both. There are several examples of successful culling strategies; Japan, South Korea, The Netherlands, Canada, the US and others have managed to control the HPAI through an efficient eradication program based on culling.
Hong Kong, the US and Italy are clear examples of successful eradication strategies against HPAI H5 and H7 outbreaks, based on vaccination.

The effect of vaccination
There is strong scientific evidence on the efficacy of AI vaccines in poultry. However this does not count for all vaccines and it is of paramount importance that vaccines comply with the OIE Manual of Standards. The experience in Hong Kong (Nobilis Influenza H5, Intervet) showed that eradication with vaccination is a viable strategy. Since the implementation of the vaccination program, no more cases in poultry and people occurred. After intensive monitoring there was no evidence of asymptomatic shedding of the virus. Vaccination, as part of the overall control program blocked transmission on commercial farms; this has been confirmed in various research trials. Although vaccinated birds, after heavy challenge, can still excrete limited amounts of virus, they were not able to infect other vaccinated birds as from seven days after vaccination.

To vaccinate or not
Objections to vaccination tend to be based partly on the fear of further spread of the virus amongst vaccinated birds and also on fears from the poultry industry in exporting countries that vaccination will lead to trade problems.

Vaccination has proven to be essential in containing and eradicating diseases. Classical Swine Fever and Foot and Mouth Disease have successfully been eradicated in Europe, with vaccination in several countries. These successes date from the previous century, when the scientific state of knowledge was certainly not as advanced as today. However, in spite of this perceived lack of scientific know-how, the vaccination strategy was successful. At present, we have much greater knowledge about epidemiology, vaccination and diagnostics and better access to both vaccines and excellent diagnostic tools. However, the extreme reluctance to apply these vaccines suggests that the scientific knowledge has overcome our common veterinary sense, which was so successful in the vaccination strategies of the past centuries.

The poultry industry fears it may have an unfavourable influence on their ability to compete on the international market. Import restrictions may arise in case of vaccination, either based on genuine fears about the virus being introduced through products from vaccinated birds or because of trade politics. The fear about introduction of the virus can be addressed, however. The OIE Animal health Code describes the standards for international trade of products from birds, vaccinated against AI. These standards guarantee that import of the virus with poultry products will not occur. If vaccination is misused as a trade hurdle, the issue should be addressed in the political field and not only in the animal health field. The EU can do more to support countries that for sound veterinary reasons choose to vaccinate and to comply with OIE standards, and that still encounter trade problems. Such trade restrictions clash with the rules of free trade under the World Trade Organisation, for which the OIE sets the technical standard.

Vaccination is not perfect, nor is culling. It is the overall program that has to bring the success. Avian Influenza is on the move, both geographically as well as biologically, and all available tools should be used to contain it. We can no longer afford to ignore such a powerful tool as vaccination.

Emergency preparedness
Emergency preparedness is essential and a lot has been done and still is being done to prepare for a pandemic. Contingency plans are in place to prepare for a potential outbreak in poultry. However, within the EU relatively little is being done on poultry vaccine banks. If vaccination is to be an important part of a contingency plan, it is urgent that vaccine banks are established in peace time.

Emergency preparedness still assumes, however, an outbreak in poultry or even a pandemic. Prevention is better than cure. Equally essential is to fight the virus at its source in poultry in those countries where the disease is present right now. Whether this is close to the political borders of the EU or far away in Asia is not relevant. Efforts to prevent a pandemic have to be undertaken worldwide.

In 2006, spending within the EU is not in line with the main challenge – to prevent a pandemic. While enormous amounts of money are spent on national and EU capacity to deal with a pandemic, much more could be done to control AI at the source in poultry.

A more aggressive approach
The international and national measures have not been effective in containing the virus in Asia. Culling strategies were successful in countries with a very good veterinary infrastructure and sufficient funds to carry out the culling program, but in others the disease has become endemic. It is in the interest of AI-free countries to apply much more aggressive efforts towards large-scale vaccination programs. Furthermore, it is of paramount importance that the vaccines comply with OIE standards and that manufacturers demonstrate that their vaccines are indeed effective in reducing virus excretion and block transmission.
The EU needs to substantially increase the financial support to vaccinating countries to increase the capacity for large-scale vaccination programs, both in terms of availability of vaccines and in terms of infrastructure to enable these campaigns.

The availability of vaccines can be increased by providing funds for the purchase of vaccines demonstrated to be compliant with OIE standards. The funding of local vaccine manufacturing facilities requires careful consideration. Upgrading local manufacturers to OIE standards is a major undertaking and a thorough assessment must be made on how upgrading is possible, the risks involved and whether the facility will be able to sustain the improved standards in the future.

For further information please contact Paul van Aarle DVM at paul.vanaarle@intervet.com or visit www.avian-influenza.com

More information on data on vaccination is available at: www.avian-influenza.com