Global Zoonotic Disease Surveillance: An Emerging Public Health and Biosecurity Imperative

The proliferation of disease pathogens that can infect humans, livestock, wildlife, and other animals increasingly threatens biodiversity and environmental security, and has collateral impacts on human health and international commerce. Globalization means that physical distance from outbreaks of zoonotic diseases—even distances spanning half the globe—can no longer be considered a safeguard against infection from those diseases. The unexpected resurgence in human deaths from H5N1 avian influenza in Vietnam and Thailand during August and September 2004 and the first evidence of direct human-to-human transmission of this potentially deadly zoonotic disease clearly demonstrate the need for international cooperation and collaboration in the identification, monitoring, and control of zoonotic diseases around the globe.

The SARS (severe acute respiratory syndrome) virus, H5N1 avian influenza virus, Nipah virus, and Ebola virus are only the most widely publicized examples of a growing list of emerging infectious diseases transmitted between wild animals and human beings, often with domesticated livestock or human commensals such as rats and pigeons involved in the chain of infection and transmission (Guan et al. 2003). The globalization of industrial livestock production and the rapidly expanding international trade in animals and animal products from wild and domesticated species are fostering the emergence and global proliferation of new zoonotic diseases with the ability to pass between and among humans, wildlife, and domesticated animals. Recent increases in the emergence and proliferation of pathogens are being driven by human transformations of natural landscapes for agriculture and livestock production, human selection through indiscriminate or inappropriate uses of antibiotics, deliberate and accidental introductions of exotic invasive alien species, and a $6 billion global trade in exotic animals and plants.

Rapidly expanding and increasingly concentrated populations of humans and livestock are fostering the emergence of virulent zoonotic pathogens that may cause fatal disease in humans and animals. Diseases like tuberculosis and polio, which were once thought susceptible to global eradication, are reclaiming lost ground, while viral diseases of humans and animals are evolving new strains that go undetected and thus thwart regional and global vaccination programs. The ancient scourges of anthrax and plague are proliferating once again in areas of Africa and Asia beset by drought, poverty, war, and civil strife.

The history of rinderpest in Africa, where the devastating loss of livestock and game animals caused widespread famine, shows that outbreaks of disease in animals may prove just as lethal for indigenous peoples and pastoral communities as human diseases like smallpox or pneumonic plague. The 2003–2004 avian influenza pandemic in Asia was unprecedented in its severity and geographic scope, with exceptionally high virulence in avian as well as human populations. Death rates among confirmed human victims of the H5N1 avian influenza virus in Vietnam and Thailand (> 70 percent mortality) are comparable to those reported among human cases of the Ebola virus in central Africa and Nipah virus in Bangladesh. Emerging and endemic zoonotic diseases are demonstrably no longer a safely distant, third-world health phenomenon. The past several years have seen an astounding resurgence of zoonotic diseases as public health threats in the United States, including

• Emergence of tick-borne Lyme disease as a significant public health problem in the suburban landscapes of the eastern United States

• The appearance of West Nile virus in New York City and its rapid spread throughout the temperate regions of North America and southward into the Caribbean and Central America, with significant impacts on populations of wild birds and mammals, horses, and humans

• The introduction of monkeypox, a formerly obscure zoonotic disease from the rain forests of central Africa, into the United States through the exotic pet trade

In addition to the threats presented by emerging and rapidly evolving natural disease organisms are those posed by laboratory cultures of genetically modified, weaponized strains of disease pathogens created and developed for use as biological weapons against humans, domesticated livestock, or crops. The anthrax “letter bomb” attacks of September–October 2001 demonstrated the critical need for recognizing that zoonotic disease surveillance and information systems are important elements of our public health and homeland security infrastructure, the nation's first line of defense and response against terrorist attacks involving bioweapon diseases (Dudley 2003). The deliberate or accidental release of weaponized disease pathogens could have devastating direct effects on biodiversity and agricultural productivity—and possibly even more devastating indirect effects on wildlife, including some endangered species, should these become targeted for extirpation because they could become reservoirs or vectors of bioweapon disease pathogens.

There is currently no single entity within the government with “command and control” responsibility and regulatory authority for managing the growing nationwide health problems associated with diseases that are passed between wildlife, domesticated animals, and humans (Benjamin et al. 2003). Federal agencies in the United States that have a role in the international monitoring of zoonotic and animal diseases of public health significance, or regulatory authority over potential means through which such diseases could be introduced from overseas, include the US Department of Agriculture's Animal and Plant Health Inspection Services, the Centers for Disease Control and Prevention, the US Public Health Service, the US Fish and Wildlife Service, the US Geological Survey, the Department of Homeland Security, the Department of the Army, and the Department of Defense. Each of these federal agencies has at least two, and in some instances four or more, different component organizations involved in the prevention, monitoring, surveillance, evaluation, identification, or control of zoonotic pathogens or foreign animal diseases.

International organizations, multilateral organizations, nongovernmental organizations, and national organizations involved in zoonotic disease surveillance monitoring efforts include the World Health Organization, the United Nations Food and Agriculture Organization, the World Organisation for Animal Health (formerly known as the Office International Epizooties, or OIE), the IUCN–World Conservation Union, and the newly chartered European Centre for Disease Prevention and Control.

Although there is considerable cooperation and collaboration among individuals within the infectious disease surveillance and response communities, the degree of formal organizational collaboration and coordination is frequently limited. None of these entities has the mandate or mechanisms to actively seek out and disseminate information on emerging wildlife diseases and zoonoses to all interested public and private sector organizations and agencies.

Those government agencies and multilateral organizations that do perform such functions typically operate under institutional or diplomatic constraints that do not permit the dissemination of critically important “unconfirmed” information on disease outbreaks. Yet such information could constitute an early warning system for diseases such as avian influenza or citrus sudden-death virus, for which the confirmation of outbreaks through official channels may be suppressed. Governments may, for example, seek to avoid externally imposed bans on the export of economically important animal or plant products, as happened with the pandemic outbreaks of avian influenza in Asia during 2003 and 2004.

Decisionmakers and governments must be encouraged to achieve greater levels of effectiveness in the surveillance and monitoring of infectious diseases in humans, wildlife, crops, and livestock. Information technology tools and methods now available can enhance communication and coordination among all stakeholders in the wildlife health, agriculture, and public heath sectors—including federal and state government agencies, multilateral organizations, the public health community, nongovernmental organizations, private sector corporations, and scientific and professional organizations. For such efforts to be effective, however, clear policy mandates must be in place to encourage and ensure the rapid worldwide sharing and dissemination of information on infectious disease outbreaks.