Human, Animal, Ecosystem Health All Key to Curbing Emerging Infectious Diseases
Bridget M. Kuehn
JAMA. 2010;303(2):117-124.
In 2006, bagged fresh spinach contaminated with Escherichia coli O157:H7 caused about 200 cases of confirmed illness across the United States and at least 3 deaths. An investigation tracing the source of the contamination ultimately implicated domesticated animals, wildlife, and environmental factors.
The case was one of many highlighted at a November summit hosted by the Institute of Medicine and the National Research Council, along with the One Health Commission, a nonprofit organization working to improve collaboration between the fields of human, animal, and ecosystem health. Lonnie King, MS, MPA, DVM, dean of the Ohio State University College of Veterinary Medicine in Columbus, explained at the summit that scientists found genetically identical strains of E coli in both cattle raised near the spinach and in wild hogs. But it took the work of ecologists and hydrologists to explain that unusual weather conditions may have allowed animal feces tainted with E coli to contaminate ground water and the irrigation system on the affected farm.
King, former head of the US Centers for Disease Control and Prevention's (CDC’s) National Center for Zoonotic, Vector-borne, and Enteric Diseases (NCZVED), said that such interdisciplinary collaborations are becoming essential to identifying and preventing infectious disease. "This investigation only succeeded when integration [of human, animal, and ecosystem health efforts] took place," he said.
Yet despite growing recognition of the need for a "one health" approach to emerging infectious diseases, a lack of infrastructure, fragmented oversight in the United States and worldwide, and a workforce that has not been prepared to work across disciplines remain major obstacles. Speakers at the summit, which included representatives of the US Department of Agriculture (USDA), the US Food and Drug Administration, the CDC, the US Agency for International Development (USAID), the National Institute on Environmental Health Sciences, as well as experts in wildlife management and veterinary medicine, outlined these challenges and ways to overcome them.
The meeting was especially timely, coming on the heels of the September release of an Institute of Medicine (IOM) report commissioned by the USAID to assess the current global system for monitoring zoonotic diseases. The report found substantial gaps in such monitoring and recommended that the United States help lead an international effort to identify and manage such disease threats more effectively (http://books.nap.edu/
INADEQUATE SURVEILLANCE
At least 65% of recent major human infectious disease outbreaks have had animal origins. including HIV/AIDS, SARS, and the currently circulating 2009 influenza A(H1N1), according to the IOM report.
A variety of factors are contributing to emerging infectious diseases. Ali Khan, MD, MPH, acting director of the NCZVED, noted at the summit that climate change is allowing potentially infectious agents to spread beyond their typical ranges. For example, tropical fungi have been found living in the Pacific Northwest and equine encephalitis, a vectorborne illness, has been found in Maine and Vermont for the first time. Another summit presenter, Karen Becker, DVM, MPH, senior veterinary public health advisor in the USAID's African bureau, noted that civil unrest and economic conditions can also contribute. For example, crowding and poor conditions can foster disease spread in refugee camps, and residents of poor communities may turn to bush meat hunting for income or to provide protein for their families.
And such problems are no longer contained within the communities where they begin; international travel can allow infections to spread rapidly to other parts of the world, King said.
"This is the perfect microbial storm," he said.
Yet the surveillance systems in place to identify such emergent infectious diseases are fragmented. Separate systems are used to detect outbreaks among humans and animals and there is little communication between the two, according to the 2009 IOM report. For example, in 1999 a veterinarian at the Bronx Zoo alerted human health authorities to the possible connection between bird die-offs and a human outbreak of febrile illnesses occurring simultaneously. However, human health officials were slow to investigate the potential connection in what turned out to be the emergence of West Nile virus in the United States.
Additionally, although disease surveillance laboratories are heavily concentrated in the United States and Europe, most diseases are emerging in developing countries, where there may be little or no surveillance. As a result, many emerging diseases are not identified until they have spread widely in human populations. King explained that preventing this scenario will require identifying disease outbreaks in animals before they spread to humans and identifying environmental disturbances that contribute to disease emergence in animals and taking preventive measures.
Improving surveillance of emerging zoonotic diseases will take a coordinated global effort. Given the large impact such diseases can have on public health and the US economy, the IOM report recommends that US officials take a leading role in the effort.
Creating such a network would require a large and continued investment, which is estimated at $800 million per year. However, over the past decade alone, zoonotic disease epidemics have caused more than $200 billion in economic losses worldwide, the IOM committee notes.
"A global zoonotic disease surveillance system to reduce the emergence of zoonotic diseases in humans and help detect other livestock diseases early could help to prevent the staggering economic losses associated with zoonotic disease outbreaks," the report states.
BUILDING A GLOBAL NETWORK
The IOM committee laid out 12 recommendations, emphasizing 3 top priorities for developing a global surveillance system. As a first priority, the committee suggests that the US Department of Health and Human Services, the USDA, the Department of Homeland Security, and the Department of the Interior work together and with the private sector and nongovernmental organizations to create an integrated system for identifying and responding to emerging diseases in human and animal populations. Additionally, these governmental agencies, the Department of State, and the USAID should collaborate with international organizations such as the World Health Organization, the Food and Agriculture Organization of the United Nations (FAO), and the Office International des Epizooties (OIE) to build a more effective global surveillance network.
Another top priority identified by the committee is establishing a sustainable means of financing such a surveillance system. It recommends that the USAID work with international finance institutions and others to achieve this goal, perhaps by imposing a tax on meat imports. Additionally, the committee recommended that the USAID work with the United Nations and other organizations to establish a coordinating body to oversee global disease surveillance.
Some nongovernmental organizations and US and international agencies have already begun efforts to promote better surveillance and more cooperation between disciplines.
The One Health Commission was formed in August 2009 with representatives from the American Medical Association, the American Veterinary Medical Association, the American Society for Microbiology, the Association of Academic Health Centers, the Association of Fish and Wildlife Agencies, the American Public Health Association, and representatives of veterinary and medical education associations to develop an integrated public health strategy.
In 2006, the FAO launched the Crisis Management Center in Rome to monitor and respond to emerging animal diseases with more than $5 million in US funding and 5 veterinary staff provided by the United States. One of the center's key priorities has been tracking highly pathogenic H5N1 avian influenza, in part, by monitoring wild bird populations and markets in which wild and domesticated birds are sold, said Doug O’Brien, JD, senior advisor to the Secretary of the USDA. O’Brien noted that the USDA has also signed an agreement to promote better coordination between the USDA and the FAO, and has invested substantial funds in promoting animal health globally.
In 2008, the USDA and the CDC entered into an agreement to launch a pilot program to monitor influenza in pigs. Laboratories of the USDA are now also testing samples from other species for the currently circulating influenza virus. Transmission of diseases from humans to animals is another important component to emerging zoonotic illness, Khan said, noting that there have been confirmed cases of 2009 influenza A(H1N1) transmission from humans to ferrets and domestic cats, and one suspected case of transmission to a monkey. In addition to the impact the infection might have on animal health, such transmission is a concern because of the potential for the virus to undergo genetic reassortment with animal influenza viruses and possibly become more virulent.
The CDC has also begun working to identify disease emergence hot spots to help direct the USAID-funded FAO, World Health Organization, and OIE monitoring and response activities to the areas in which they are likely to be most effective.
"We are trying to get away from an old strategy of looking everywhere or looking haphazardly," Khan said, and instead engage in "systematically thinking about this to form a risk-based strategy."
Additionally, the CDC has launched a program to assign veterinarians with human public health experience to international agencies and hot spots around the world, Khan said. So far, such individuals have been assigned to the OIE's offices in Paris, to the FAO crisis center in Rome, as well as to locations in Bangladesh, Nigeria, and Vietnam. During the next 2 to 3 years, the agency hopes to expand the program and increase the number of individuals and extend their presence further in southeast Asia, Africa, and South America.
"It's more than just recognizing disease emergence at the interface of human, animal, and environmental health," Khan said. "It's really about looking beyond humans for opportunities for prevention. That is where we are going to have the most impact on global health."
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