Bird Flu Basics for Duck Hunters

Avian influenza, bird flu, pandemic, highly pathogenic, H5N1 virus—what does all this mean to duck hunters and waterfowl conservation?

By Bruce Batt, Ph.D.

The press is bombarding us with information as a new strain of bird flu has devastated domestic poultry by the hundreds of millions in Southeast Asia and has, in a few cases, sickened or killed people. This is a bird disease that has spread over parts of Asia, Europe, and North Africa, and many experts believe its arrival in North America is inevitable. Some think it will happen this year. One way the virus could arrive is to be carried by waterfowl and other wild birds. Therein lies the connection with waterfowl and the threat to waterfowl conservation in North America, even though there has never been a case in which the disease is known to have been transmitted from a wild bird to a human.

WHAT IS AVIAN INFLUENZA?

The term avian influenza refers to viruses that occur in birds. Birds easily shake off most strains of bird flu, and most types have low pathogenicity (ability to produce disease). But genetic mutation occurs frequently in viruses, and sometimes a harmless virus will change to one that is highly pathogenic and can cause severe sickness and death. This is what has happened with the emergence of the strain of bird flu that is causing worldwide concern among poultry scientists, human health experts, and waterfowl managers. The new strain, which was identified in 1996, is known as the Asian H5N1 virus.

WHAT DOES AVIAN FLU HAVE TO DO WITH HUMAN HEALTH?

Rarely is an avian flu transmitted from birds to other kinds of animals. But the new Asian strain has infected more than 200 people, mostly in Southeast Asia. Almost all of them caught it directly from domestic poultry. More than 100 people have died—a very high mortality rate for any flu. By comparison, a few million Americans get the “normal” flu every winter, and an average of 36,000 die each year.

In nearly every case studied, people infected with the Asian bird flu have lived and worked in close contact with domestic poultry where they shared the same air, soil, and water. This degree of exposure is highly unusual in developed countries where poultry are generally raised in large sanitary “factories.” There have been at least three instances where the virus has been transferred from human to human within families. But even though in its present form the virus infects humans only with difficulty, additional mutations could allow it to spread more easily from human to human, eventually becoming widespread in people. This situation would be called a pandemic.

Even if such a genetic change were to occur, the mutated virus might be less virulent in people in its new form. Or, it could be just as deadly as the current form, and that’s why human health authorities are so concerned. They must prepare for the worst-case scenario because the consequences of failing to do so could be severe. That’s why we see bird flu in the news so much. International agreements have dedicated several billion dollars to everything from vaccine development to trade restrictions and surveillance of wild birds. These actions carry significant political and economic implications and are thus big news.

HOW ARE WILD WATERFOWL INVOLVED?

Wild birds, including waterfowl and other water birds, are sometimes killed by the new strain of bird flu, but most of them appear to be resistant. As a result, some can become carriers of the disease—that is, they have the disease in their bodies but are not sick and live normally. In this condition, infected birds may carry the disease to other locations and affect other wild and domestic flocks. Nevertheless, in almost every case where wild birds have died from the disease, the origin has been traced to infected flocks of domestic poultry. There are a few cases, however, where the disease arrived in remote locations where it was more likely transported by wild birds.

Although Asian H5N1 can be lethal to individual wild waterfowl, only a few large die-offs have occurred in the wild. The most serious happened in western China last summer when more than 6,000 wild birds died in a nature preserve. Among these were 2,000 bar-headed geese, an endangered species in Asia. This represented about 20 percent of the world’s known population, so the loss was significant for this species.

Beyond this case, most other outbreaks in wild waterfowl this past winter typically killed a few individual birds and rarely more than a few hundred. This is a bit of “good” news, as it lessens the concern that massive die-offs of waterfowl, in the hundreds of thousands or millions, are likely to occur if the disease comes to North America. We are still concerned about the effects of the disease, however, because of the large concentrations of ducks and geese that we see in North America during migration and winter.

A recent United Nations report recommended that protecting and restoring wetlands was a sound mechanism for dispersing large concentrations of wild birds to help keep them away from domestic flocks. For seven decades, DU has been advocating wetland conservation for different reasons. Such independent advocacy for wetlands is welcome and could benefit waterfowl in the long term.


Another concern among sportsmen and waterfowl managers is that some groups might advocate culling wild birds to prevent them from spreading the disease. This possibility has been thoroughly reviewed and opposed by international conservation organizations and by public health authorities across the world. The official position of both the U.S. Fish and Wildlife Service and the Canadian Wildlife Service is that such an action is out of the question. Large-scale culling is how diseases are stopped from spreading among domestic flocks where they are confined and every bird can be slaughtered. In the wild, such a campaign could never eliminate every bird in every targeted flock and would simply cause carrier birds to disperse to other areas.

The overwhelming concern with wild birds is that they might transmit Asian bird flu to domestic poultry flocks. The threat to domestic birds is huge with profound economic and food supply implications—but wild ducks and geese are not a threat to human health. Wild birds have never been shown to transmit the disease to people, and health officials consider this type of transmission highly unlikely.

HOW MIGHT ASIAN BIRD FLU GET TO NORTH AMERICA?

As this article was written in early June, Asian bird flu had not been detected anywhere in North America. Most authorities and biologists expect the virus to arrive by being transmitted in illegally imported poultry and poultry products or secondarily by wild birds that move between continents in the Northern Hemisphere. If avian flu ever becomes transmittable from human to human, it would almost certainly be transferred by airline passengers who unsuspectingly picked up the virus while in a foreign country and then carried it home on commercial aircraft—the prevalent way annual flu outbreaks are carried to this continent every year.

The wild bird connections are most likely to occur between Russia and Alaska, where more than 26 species of birds are known to regularly move across the Bering Sea. Some of these birds breed in Alaska and winter in China, Japan, and even Australia and Southeast Asia. Others breed in northern Russia and winter on the west coast of North America. There are also a few connections across the Atlantic with birds that winter in western Europe and breed in northern Canada and Greenland.

On March 20, the U.S. secretaries of the Interior, Agriculture, and Health and Human Services  announced a $29 million surveillance plan to search for the disease this year, in every state, in live wild birds, hunter-harvested birds, sentinel birds, and selected wetlands across the country. Between 75,000 and 100,000 samples will be taken and tested for Asian bird flu. The details of the national program can be studied at this website. For more about surveillance efforts in Alaska, click here, and for programs under way in Canada, see http://wildlife1.usask.ca/en/CCWHC_home.php.
 
With such surveillance efforts in place, there is a good probability the disease will be detected if wild ducks and geese carry Asian bird flu to North America this year.

IMPLICATIONS FOR WATERFOWL HUNTERS

So where does this leave the North American duck hunter? A couple of countries in Europe and Asia closed their spring hunting seasons this year. Might that happen in North America?

Obviously, the best scenario is that the Asian bird flu does not show up in North America. But even if it is discovered in wild birds in North America, not much is likely to change related to hunting seasons. The world’s health experts continue to stress that this strain of Asian bird flu has never been transmitted from wild birds to humans, so even if a hunter shoots and subsequently handles a bird carrying the disease, transmission of the virus is not very likely to occur. Nevertheless, hunters should use commonsense precautions when cleaning game.

The U.S. Fish and Wildlife Service does not anticipate closing waterfowl hunting seasons based on what is currently known about this form of bird flu.

LOOKING AHEAD

Nobody knows how the bird flu threat will play out in the next few months and years in domestic birds, wild birds, or humans. The greatest of all threats would be for the disease to evolve into a lethal form that is easily transmittable from human to human. Such a mutation has not occurred, and even the world’s experts in human health don’t agree on how likely that possibility is.

Nevertheless, it could happen, so authorities have no choice but to prepare for the worst. These efforts have sparked an explosion of media coverage this year.

Whatever happens, the ducks will endure, responding to the seasons, the weather, and their habitats as always. Whether this threat turns out to be no more than a scare with the disease showing up in a few wild birds or something as extreme as a human pandemic, it will pass. For the ducks, life would return to normal fairly quickly. In the unlikely event that waterfowl hunting were to be disrupted in some way by avian flu, it would be vitally important not to allow the tremendous progress being made in waterfowl habitat conservation to be severely interrupted. We must sustain our commitment to the long-term conservation of waterfowl habitats by supporting organizations like Ducks Unlimited, buying duck stamps, and pushing for favorable policies in the Farm Bill and funding for the North American Wetlands Conservation Act, while also supporting state and provincial programs that help assure the future of waterfowl. Under such a scenario, Ducks Unlimited would do everything possible to sustain our most important work and is preparing contingency plans to guide the organization through several different levels of impact.

For duck hunters and managers, the most important things to do will be to watch the progress of bird flu surveillance programs and keep up with other developments as they occur. Ducks Unlimited will help you follow this issue by diligently reporting significant news on www.ducks.org/birdflu. DU’s website also provides helpful links to other sources of information from across North America and the world.

In the end, each of us will make our own decisions about how we will react to future developments. With what I know now, I intend to handle the birds I harvest a little more carefully than I used to—as I actually  should have been doing all along. Otherwise, I plan to carry on enjoying this spectacular resource as much as I possibly can, restrained only by the normal things—my budget and available spare time.

Dr. Bruce Batt is chief biologist at DU’s national headquarters in Memphis.