The threat of potential pandemics such as Ebola, SARS, and avian influenza demands a more holistic approach to disease control, one that prevents diseases from crossing the divide between humans, their livestock, and wildlife, according to the Wildlife Conservation Society (WCS) in the most recent issue of the journal Foreign Affairs. This "One World, One Health" concept, as described by WCS veterinary staff, calls for the integration of efforts to deal proactively with disease threats to human and animal health before they reach crisis levels.
"As of yet, no single agency or organization focuses on the myriad diseases that move across the interface between people, their domestic animals and wildlife," said Dr. William Karesh, one of the co-authors of "One World, One Health" and the director of WCS' Field Veterinary Program. "There is only 'one health,' and future programs must factor in the complexity of how emerging diseases move among humans and other species."
The paper--titled "The Human-Animal Link"--is one of several in the July/August issue of Foreign Affairs focusing on pandemic diseases.
Karesh and co-author Dr. Bob Cook--WCS vice president and chief veterinarian of the society's Wildlife Health Center--developed the "One World, One Health" concept in response to the increased vulnerability of humanity and animals to a host of diseases that are capable of adapting to other species and moving across the globe through the rapid transportation of goods and people. Many of these diseases can move back and forth between species, mutating into more virulent, resistant forms. Over 60 percent of the 1,415 infectious diseases currently known to modern medicine are capable of infecting both humans and animals. Most of these diseases originated in animals and now infect people.
On the local level, the communities that rely on wildlife for their protein are vulnerable to pathogens from the forest. The AIDS virus may have entered human communities through the consumption of non-human primates with a similar virus that mutated. In Central Africa, many subsistence hunters will take advantage of animal carcasses for protein, often infecting themselves and their families with deadly diseases in the process. Each human outbreak of Ebola in Central Africa during the late 1990's and the first years of this century can be traced to humans handling infected apes. Estimates for the amount of wild, or "bush" meat consumed in Central Africa is over a billion kilograms a year, translating to an estimated 580 million individual animals alone. People in the Amazon basin consume between 67 and 164 million kilograms of wild meat a year, between 6.4 million and 15.8 million individual mammals.
On the global level, one of the biggest challenges to health organizations and agencies is the worldwide trade in wildlife. According to a variety of sources compiled by WCS, the annual global trade in live wild animals includes roughly 40,000 primates, 4 million birds, and 640,000 reptiles. These species and the diseases they carry are brought together into trading centers before being sold locally, or shipped to other regions of the world. Avian influenza--currently feared as one of the most likely candidates for a pandemic--was detected in two mountain eagles that were smuggled into Belgium to Thailand in carry-on baggage. Livestock movement can introduce diseases also. Tuberculosis--a disease afflicting domesticated cattle and humans--has now spread across continents, infecting wild bison in Canada, deer in Michigan, and Cape buffalo in South Africa.
The costs of reacting to these problems, say Karesh and Cook, are staggering. The rash of livestock pathogens that have spread around the world in the last decade--a list including mad cow disease, foot and mouth disease, avian flu, swine fever) have caused some $100 billion in losses. The recent outbreaks of SARS have cost the global community half that amount.
To address these problems, Karesh and Cook call for a number of steps to integrate human and animal disease prevention efforts in a coordinated manner. Recommendations include better surveillance of wildlife diseases to prevent outbreaks before they occur, shifting the cost of preventing and controlling outbreaks to animal traders, encouraging governments to improve the regulation of the animal trade and breaking down barriers among health disciplines.
"Diseases that afflict people, livestock and wildlife have severe economic and social consequences for all regions of the world," said Dr. Bob Cook. "Failing to implement a cross-species, planet wide approach to these emerging health issues will cost more than we can afford. The 'One Health' paradigm can serve as an 'ounce of prevention' for the 21st Century."
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