In the absence of news reports, bird flu might seem to have flown the coop. Unfortunately, it never actually went away—and is now worse than ever. "There are more flu infections in more countries than ever before," said veterinarian William Karesh, head of the Field Veterinary Program of the Wildlife Conservation Society (WCS), during a WSC conference in New York City last week.

According to the World Health Organization (WHO), 381 people worldwide have been infected—240 of them fatally—with the H5N1 strain of bird flu since 2003. South Korea has suffered through at least eleven outbreaks in poultry this month alone, leading to the culling of 1.9 million chickens and ducks to try to keep a lid on the disease. In Egypt, 50 people, including a two-year-old boy most recently, have been stricken since 2006**; 22 of them have died.

A recent study shows that so-called zoonoses—infectious diseases such as H5N1 bird flu, West Nile and Ebola that strike both animals and people—now account for as much as 58 percent of human pathogens and the number is growing fast. In just the past five years, WHO has identified more than 1,000 epidemics stemming from such pathogens.

These diseases are hard to stop because they are not only spread by wild animals, mosquitoes and the like but, even more commonly, by billions of livestock animals, such as chickens, ducks and geese raised for food in vast factory farms. Zoonotic outbreaks are triggered by a range of factors, including man-made changes to natural habitats that bring humans into contact with wildlife as well as airplanes and other forms of transport that allow "speedy, long-range dissemination of any disease agent," says veterinarian Arnon Shimshoni of The Hebrew University of Jerusalem.

And humans are not the only ones hurt. In their haste to prevent an outbreak, jittery authorities and farmers are sometimes too quick to kill some noninfectious critters, Karesh says. "Wildlife can be killed by a disease, but, more frequently," he notes, "they are killed by humans afraid of getting a disease or afraid of their animals getting a disease."

Even the best-intentioned plans can backfire, such as a conservation scheme to link Krueger National Park in South Africa with similar parks in Zimbabwe and Mozambique. Animals carrying diseases could spread them far and wide. For instance, South African wildlife infected with bovine tuberculosis, could spread it to animals and people in the north as they move more freely across the landscape. Simultaneously, tstse flies from the north might spread trypanosomiasis* south, endangering the recently recovered largest population of white rhinoceroses in the world.

And rabies, a problem in Mozambique, might spread to infect animals in Krueger. "In an area that is ecologically naive to [a] virus, it could wreak havoc," warns veterinarian Steven Osofsky of the WCS Field Veterinary Program.

Perhaps the most telling example of the inextricable link between human and wildlife health is that of our closest kin, the great apes. In the forests of the Congo River Basin—the world's second largest intact tropical forest—chimpanzees and gorillas suffer from the same Ebola virus as humans. This hemorrhagic fever can kill as much as 95 percent of the apes it infects; it has claimed at least 5,000 western lowland gorillas in just the past two years. "The threat of Ebola alone caused the [International Union for Conservation of Nature and Natural Resources] to upgrade western lowland gorillas to critically endangered," veterinarian Ken Cameron of WCS's Field Veterinary Program in central Africa, reported at the WCS's State of the Wild conference. "We could lose 80 percent of the species in the next 10 years."

As a result, the WCS has joined forces with the U.S. National Institutes of Health, Boston University and other research institutions in an effort to adapt a vaccine against Ebola for gorillas. At least one candidate has proved effective in protecting macaques from one of the three strains of the Ebola virus but it remains unclear whether it will work in people or gorillas.

But even if a successful vaccine is developed, it will be no easy task to inoculate notoriously elusive gorillas. "We are seeing less than one tenth of one percent of the total population," Cameron said. Darting them with a vaccine then seems unlikely.

An alternative might be to inject fruit and other food that apes like to munch. But Cameron notes that it would be hard to control doses that way—and that other animals might end up gobbling the medicine. "We hope that vaccines can help, but it's too early to tell," Cameron said. "We do feel we need to try." For the gorillas—as well as for us.

"There is an artificial distinction between the health of wildlife, livestock and people," Karesh said. Sickness in one of these groups, can mean sickness in all.

*Correction (4/24/08): This article originally identified the disease threatening rhinoceroses as rabies.

** Correction (4/25/08): This article originally ascribed the Egyptian statistics to this year instead of since 2006.

5 Comments

1. 1. Steven Osofsky 05:35 PM 4/23/08

   Dear Mr. Biello- Please note that the disease of potential concern to the Kruger white rhino population that I discussed was trypanosomiasis. Rabies was discussed in another context. Thank you, Steve Osofsky, DVM

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2. 2. srchuck 07:00 PM 4/23/08

   Are we now responsible for protecting gorillas from natural pathogens as well as heart disease that develops in zoos when the zoo environment causes them to live longer than they would in the wild? I thought these situations were called evolution in action.

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3. 3. Steven Osofsky 02:55 PM 4/24/08

   Mr. Biello- I have provided a corrected paragraph for Sc. Amer. here, as it is important that these issues be portrayed accurately. I hope this is helpful: Even the best-intentioned plans require a cautious approach, such as a conservation scheme to link Kruger National Park in South Africa with similar parks in Zimbabwe and Mozambique. Animals carrying diseases could spread them far and wide. For instance, South African wildlife infected with bovine tuberculosis could spread it to animals (and/or people) in the north as they move more freely across the landscape. Simultaneously, tsetse flies from the north of the landscape might spread trypanosomiasis south, endangering the largest population of white rhinoceroses in the world. Rabies, a problem in adjacent Mozambique, for example, has never infiltrated the wildlife of Kruger. "In an area that is ecologically naive to [a] virus, it could wreak havoc," warns veterinarian Steven Osofsky of the WCS Field Veterinary Program.

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4. 4. avianmaven 06:45 PM 4/24/08

   Dear Mr. Biello: Thank your for your article that confirms that Avian flu is spread not only by livestock but by wild birds as well. Beyond Avian flu over 60 other potentially fatal diseases are carried by wild birds and their droppings. A good thing people can do to protect themselves is by purchasing humane and eco-friendly bird deterrents such as the ones offered by Bird-X, Inc. This should prevent an overpopulation of birds in any area frequented by humans. Please consider writing follow up stories related to other bird threats. Thank you.

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5. 5. Bettysenior 04:23 PM 4/26/08

   There is only one way to stop the eventual human-to-human avian flu pandemic and that is to address the killer disease at its source. In this respect vaccines are not the answer and where today we have no cure if the ugly head of bird flu manifests itself throughout global societies. Therefore the sooner we address the problem at its source preventing it ever happening, the sooner we will reach a reality check.
   
   The pandemic will happen, but our present strategy to cure rather than to prevent is totally living in a world of hope that will never happen. Unfortunately addressing the problem at its source has no real monetary income attached to it unlike drugs where billions are created in profits yearly. In this respect the world's false hope will be the death of many hundreds of millions eventually, due to the altar of profit controlling the whole system and where the only solution is not even heard properly.
   
   Dr David Hill
   World Innovation Foundation Charity
   Bern, Switzland

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