Emerging infectious diseases are commonly defined as infectious diseases whose incidence have recently increased or threaten to increase in the near future. There are various categories including new infectious agents that result from changes or evolution of existing organisms (e.g., highly pathogenic H5N1 avian influenza and multi-drug resistant tuberculosis); known infections spreading to new geographic areas, species, or populations (e.g., chronic wasting disease, and West Nile virus); previously unrecognized infections appearing in areas undergoing ecological transformation (e.g., Ebola virus and severe acute respiratory syndrome-SARS); and old infections re-emerging (e.g., bovine tuberculosis). In recent history there have been an unprecedented number of new infectious diseases that have been identified, and many of the emerging diseases that are threats to human, animal and ecosystem health are of wildlife origin. In fact, it has been estimated that approximately 75% of emerging diseases are zoonotic in origin.1
Globalization can be defined as increasing global connectivity, integration and interdependence in the economic, social, technological, cultural, political, and ecological spheres. While globalization can increase economic prosperity as well as opportunity, especially among developing nations, enhance civil liberties and lead to a more efficient allocation of resources, it can also result in unsustainable harm to the biosphere. Globalization and the associated human activities create a global environmental situation that favors disease emergence. Examples of these human activities or "drivers" of emerging infectious diseases include ecological alterations (climate change, loss of habitat and biodiversity as well as invasive species); human demographic and behavior changes; international travel and trade; microbial adaptation and change; and lack of resources to prevent and control these diseases, as well as breakdown of public health measures due to war and natural disasters.
Disease prevention is the desired method to protect the health of wildlife populations as once a disease has been introduced into a population it can be very difficult, if not impossible, to control or eradicate.2 There are very few effective wildlife disease management tools available to wildlife veterinarians, managers and conservationists. The few options available (e.g., population reduction, use of vaccines or other biologics, and environmental modification) are expensive, lack any assurance of success, and can be unpalatable to the general public. Historically, disease control and prevention has focused on the immediate cause of ill-health, i.e., controlling the infectious or toxic agent and mitigating the effects on the host. However, intervening at the level of the "driving forces" or "pressures" that promote the emergence of health threats will be the most effective point of control.3 For example, in developing countries it is often poverty, or lack of economic opportunity, that drives the depletion of natural resources that result in environmental degradation which is responsible for the emergence of an infectious agent and subsequent threat to the health of wildlife and human populations. Thus in this example, focusing on poverty reduction and sustainable development should eliminate the drivers of these diseases and prevent emerging disease outbreaks. Consequently, it is vital that relevant national and international policies such as agricultural, economic, energy, environmental, health, housing and development, trade and transportation policies, among others, appropriately balance the need for economic development with the need to protect human, wildlife and ecosystem health. Ensuring this balance is met as well as focusing on long-term action directed at mitigating the effects of the drivers of emerging diseases will not only be the most cost-effective method to prevent the emergence of wildlife diseases, but will have multiple benefits for wildlife, humans and the shared ecosystems.
Additional measures needed include the promulgation of laws and regulations that enforce this balanced approach, public education, and development of enhanced biosecurity measures. In addition, risk analysis, early-detection disease surveillance and rapid response systems will be essential to allow robust and effective responses to wildlife disease outbreaks. Considerable research is also necessary to ensure that decisions at all levels are science-based as well as to develop new disease diagnostic, surveillance and management tools. One of the biggest impediments to successful wildlife disease management is the lack of capacity to effectively address wildlife health issues, and the Association of Fish and Wildlife Agencies has developed a National Fish and Wildlife Health Initiative for the United States with the goals of developing and enhancing federal, state and territorial fish and wildlife management agency capacity to effectively address health issues, and develop and implement a national strategy to address health issues involving free-ranging fish and wildlife through management, surveillance and research (www.fishwildlife.org). International capacity building will also be vital.
Conservation medicine is a relatively new interdisciplinary scientific field that studies the relationship between human and animal health, and environmental conditions.4 Conservation medicine is at the nexus of the fields of human, animal and ecosystem health, requires professionals from diverse disciplines to work together to address these new disease threats to human and animal health from anthropogenic ecological changes, and provides a theoretical framework with which to address the problems of emerging infectious diseases and wildlife disease management discussed above. Animal health and human health are inextricably connected through the ecological realities governing life on our planet, and we need to define the appropriate balance between the needs of people, wildlife, and domestic animals in the face of finite energy, land and resources. Nothing less than the integrity of the biosphere is at risk.
1. Taylor LH, Latham SM, Woolhouse ME, Risk factors for human disease emergence. Philos Trans R Soc Lond B Biol Sci 2001; 356:983-989.
2. Wobeser GA, (2006) Essentials of Disease in Wild Animals, Blackwell Publishing.
3. Corvalan CF, Kjellstrom T, Smith KR, Health, environment and sustainable development. Identifying links and indicators to promote action. Epidemiology 1999;10:656-660.
4. Aguirre AA, Ostfeld RS, Tabor GM, House C, Pearl MC, (editors) (2002) Conservation Medicine: Ecological Health in Practice, Oxford University Press.