: Doing the right thing to do away with bird flu

    2007/07/07
Doing the right thing to do away with bird flu
By : MOHD ZAMRI SAAD

Avian influenza has raised its sinister head once again in Malaysia. There is no reason for us to fail to eradicate the disease as all steps have been put in place. But just how long will it take, asks MOHD ZAMRI SAAD.

BIRD flu hit Malaysia again this year, for the third time. In the last two rounds, we were considered lucky as it did not destroy our chicken industry, while none of the patients in contact with the dead birds contracted the deadly virus.

We seem to be lucky again this time. Only some chickens have had to be destroyed so far, while human patients have all been negative. But as we may not be lucky the next time, proper prevention, eradication and control of the disease should be in place.

Devastating Asian outbreaks of bird flu started in mid-December 2003 in Korea before spreading to eight countries by March 2004. By then, Malaysia, Singapore and the Philippines were the only countries in East Asia free of the disease.

The episode devastated the poultry industry in Thailand, Indonesia and China. Recognising the threat of bird flu, the 72nd World Organisation for Animal Health (OIE) annual general session recently added new articles for avian influenza to its Terrestrial Animal Health Code.

All the affected countries, except Indonesia and People’s Republic of China, adopted a stamping-out policy under which infected birds were destroyed and vaccination was prohibited.

Indonesia and China adopted a modified stamping-out policy of culling and vaccination. The success of control measures varies and has been influenced by many factors.

Disease prevention is considered the most efficient method of animal disease control. This involves inhibiting introduction of avian influenza virus into a country or a poultry flock.

It includes minimising direct and indirect contact between birds of the flock (chickens) and wild waterfowl, live market birds or pet birds. Consequently, bio-security is extremely important in minimising the risk of primary introduction.

In addition, efficient surveillance for the presence of the virus, antibodies or clinical signs must be put in place to ensure successful prevention of avian influenza infection.

If these steps fail to prevent the avian influenza virus from infecting the flock, eradication of the virus from the affected flock will have to be the next step.

The amount of virus produced by an infected flock can be reduced and finally eradicated by killing and removal of the affected birds, followed by culling of exposed birds.

The "stampede method" is the method of choice during early infection.

Three zones are immediately established: An "infected zone" within a 1km radius of the infected flock; a "buffer zone" of another 2km radius, and a "surveillance zone" of another 7km radius.

In the infected zone, all birds, animals and their products are destroyed. Within the buffer zone, only birds and their products are destroyed and no animal movement is allowed. The surveillance zone is intensively monitored for signs of avian influenza.

The "stampede" policy must be well supported by a quick and accurate diagnosis and a suitable compensation scheme.

Controlling avian influenza aims not to eradicate the disease entirely but reduce the amount of virus produced by an infected flock, in the hope of reducing the incidence of new birds being infected by the virus. This is practised in a country or flock that has endemic episodes of avian influenza, or has had the disease for a long time.

Since the amount of virus can be reduced by vaccination, it has become the most common method of controlling avian influenza.

Vaccinations are capable of inducing antibodies that provide protection against mortality, morbidity (incidence of the disease) and decline of egg production, and significantly reduce the excretion of virus.

Vaccination reduces the number of newly infected birds but does not entirely eliminate the disease, giving a chance for the virus to make a comeback in the future. Since vaccination is only able to reduce the excretion, the virus usually remains within the country or flock.

Therefore, in some countries, vaccines have been banned or discouraged because they interfere with the stamping-out eradication policy aimed at total removal or killing of the virus. Immunised birds can still be infected and excrete the virus without showing symptoms, exacerbating the spread of virus.

The tragedy of the Nipah virus infection in pigs in 1999, which crippled the pig industry, killed more than 100 people and changed the lifestyle of hundreds of pig farmers, was a blessing in disguise.

The outbreak caught us by surprise, when we were ill-prepared to handle such animal disease outbreaks.

Subsequently, we realised the necessity to be prepared at all times. Suitable laboratories were established by the government and private sector, equipped with state-of-the-art equipment.

Human resource development was speeded up to ensure more experts in the required areas, and co-operation among different but relevant authorities became more efficient.

Farmers and the industry started to realise the importance of animal movement in spreading the disease, and the devastating effects of animal disease outbreaks.

The government and general public grew aware of the importance of animal disease control and were ready to participate. Public education has become an important part of the agenda for both government and private veterinarians.

Are we doing the right thing? Yes. We have been a country free of bird flu, and prevention has been our policy.

Steps towards prevention have been put in place, particularly preventing animal entry from infected countries. Now that the country has been newly infected, eradication through the stampede policy is the method of choice.

All requirements for the stampede policy are in place: Government support for compensation, laboratories for quick and accurate diagnosis, availability of expert resources, legislation, and co-operation between the government and private sector.

There is no reason for us to fail to eradicate the disease. The question is, how long will it take?

Dr Mohd Zamri Saad is dean of Universiti Putra Malaysia’s Faculty of Veterinary Medicine.