Bird flu and wild ducks by Dr Matt Draisma

Excerpt from Hunter 15

There have been no reports of bird flu virus being detected in migratory birds in Australia as yet. Only one case of bird flu virus has been diagnosed in an imported parrot here held in a quarantine station, which I didn’t think should have been allowed under our strict quarantine laws but apparently is, and remains a stupid administrative oversight under the present circumstances. This import policy will, no doubt, be urgently reviewed in this light and should, in fact, have been reviewed much earlier.

The Federal animal health services are surely presently monitoring for the virus in waterbirds in our far north, where some of our waterfowl species migrate to India and Asia and back. The health authorities already have various sentinel stations operating on the Torres Straight islands and near Darwin and are monitoring for malaria, as well as insect-borne viruses such as Jap encephalitis, blue tongue virus and others. They are also monitoring rabies viruses on various migratory bat species to stop this from coming across from Indonesia.

Migrating snipe and mutton birds could be at risk of being carriers down here in the south, as they migrate from China and Siberia. Snipe population numbers here, as well as the type of habitat that they and the mutton birds both prefer here, would not be likely to facilitate the necessary close contact with our local ducks to readily pass the virus on. Nevertheless, it will be important now and in the future for all duck hunters to alert the authorities to any sudden waterfowl sickness epidemics or mass deaths should they find such, as it could implicate an exotic disease outbreak, including one caused by bird flu.

The bird flu virus is known to spread occasionally from poultry to individual humans where it can then cause a fatal lung infection. This is not due to this virus itself having great virulence but rather is due to the disproportionate and excessive reaction of the human immune system to this particular virus strain and the resultant auto-destruction, which greatly increases the body damage and often makes it fatal to humans. The fear is that once a human is infected, the virus will mutate and begin to pass from human to human. So far this has not happened with any of the known bird-to-human infections, some of which the human victims have survived. The bird flu virus is spread aerially in faecal dust from the birds feathers, usually by flapping wings in intensive domestic poultry sheds (or at slaughter), but also by a multitude of other ways described below, to be directly inhaled by other birds or their human handlers.

South-east Asia is a high risk spread area for bird flu because of the culturally close contact between live domestic poultry (mainly chickens and ducks) and humans - both in rearing facilities in high-density urban areas, in the home and at local produce markets. A lot of these people buy live poultry from densely-packed marketplaces, transport them live on high human density public transport or on motorbikes, home kill and dress them for personal consumption (including portions of the offal). This is the best way to guarantee their freshness, which is important in hot, humid climates when refrigeration is often unavailable. This multiple close contact greatly facilitates human exposure.

Domestic pigs are also intensively kept under similar circumstances in these countries. Many of our annual human flu virus strains emerge from mild and often symptomless pig or bird (chicken or domestic duck) flu virus strains in this Asian flu virus breeding cauldron. These flu viruses infect humans annually, the virus strains are monitored and vaccines are annually made from new strains for use on the old and young. The difference with the present particular bird flu strain is that it is highly virulent and lethal to birds.

The bird flu virus itself is quite fragile and does not live long on exposed surfaces, even on the hands. Dressing ducks as we do, by skinning and breasting them, avoids having to even touch the gut, and also removes the skin with its surface contaminants. Risk of gut spillage during the dressing is thus nil using this method. Shot perforation and subsequent leakage of gut contents onto the meat is also easily detected once the skin is off. Such contaminated sites may be radically trimmed or the entire carcass can then be discarded.

Wearing disposable gloves followed by hand washing with soap after dressing ducks, as we already do, is sufficient at present to control most risk of virus exposure. As an added precaution we can swap the soap for any type of mild disinfectant.

If the virus enters the wild duck population in Australia then all is not lost either. The additional wearing of face masks and outer protective clothing would then be advisable when handling and dressing wild duck carcasses and would not present too many problems.

Any bird flu virus-affected birds usually die rapidly (and often in large numbers) after exposure. Any healthy and active wild birds will therefore have a low risk of being infected at the time they have been shot. Birds that remain on the water when the shooting starts or that are slow to fly up, should always be treated with caution and discarded, rather than consumed as they may possibly be infected or be sick with something else (or they may be young, naïve birds). Both freezing and cooking easily kills the bird flu virus, so early undetectable infections in birds that are still well when shot, pose no risk for consumption if handled in the prescribed manner.