Bird flu: a new sampling campaign is planned in Africa

Asia, Europe, Africa... The bird flu epidemic has not needed a passport to cross borders, but has almost certainly required a vector.

What sort? This is one of the questions that is still bothering researchers. Migrating wild birds have been at the heart of the debate on the matter ever since the crisis began. However, we also know that legal and illegal trade circuits play a major role in disease spread within countries.

For Emmanuel Camus, Director of CIRAD's Animal Production and Veterinary Medicine Department, "both types of vector are suspected. The balance may swing one way or the other, depending on the situation ". While legal trade circuits are more or less familiar, it will be less easy to evaluate the role of illegal circuits. As regards the role of migrating wild birds, an initial campaign of 5000 samples has been conducted by CIRAD, in conjunction with the NGO Wetlands International and the FAO, in 14 countries since January 2006. Their analyses have not revealed any trace of the highly pathogenic H5N1 virus to date. However, we cannot state with any certainty that wild birds are not responsible, since we do not yet have certain data. Conversely, the analyses did reveal the existence of other less pathogenic avian viruses, and provided further information about the ecology of the bird flu virus in the tropics.

A new sampling campaign is scheduled in Africa as of September 2006, at more sites. Moreover, research recently showed that while bird flu viruses are generally found in the cloaca, H5N1 concentration is even higher in the respiratory tract of infected birds. In the next campaign, samples will thus also be taken from the larynx of each bird.

This new sampling operation will be facilitated by better local infrastructures: Africa will shortly have some ten laboratories capable of diagnosing the disease, compared to just one at the end of 2005. Moreover, the CIRAD "Control of Emerging and Exotic Animal Diseases" Research Unit's analysis laboratory in Montpellier should have automatic equipment by the autumn, enabling it to handle up to 400 samples a day and provide more rapid diagnoses.

Over and above the existence of the virus within flocks, researchers also need to understand intracontinental bird movements in particular. In effect, in addition to migration patterns, which have been known for some time, there are also bird movements within Africa, particularly from West to East and South to North, that may play a significant role in spreading the disease. To determine that role, CIRAD is planning to work with Wetlands International and the Wildlife Conservation Society to capture birds early this coming winter and fit them with very lightweight satellite transmitters so as to monitor their movements.

http://www.cirad.fr