Sustaining Global Surveillance and Response to Emerging Zoonotic Diseases (2009) / Chapter Skim
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3 Drivers of Zoonotic Diseases
3 Drivers of Zoonotic Diseases
Pages 77-114
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From page 77... ...
Regions where these factors are most densely aggregated, most highly prevalent, and where risk of a disease event are most intense can be considered zoonotic disease "hotspots." In this chapter, the committee reviews many of the drivers underlying this process of disease emergence and reemergence. Though not an exhaustive review, it reveals the multiplicity and the complexity of their inter-relationships.
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From page 78... ...
. A recent analysis of food-animal production data from the index site -- a commercial pig farm in Malaysia -- before and during the outbreak shows that the emergence was likely caused by repeated introduction of Nipah virus from the wildlife reservoir into an intensively managed, commercial pig population site planted with mango trees (Daszak et al., 2006)
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From page 79... ...
Disease Emergence Re - emergence Persistence Environmental Domain Animal Domain Long -term Climatic Change Non-human Animal Health Issues Global Weather Influences ( ENSO) Behavior, Geographic Range, Local/ Regional Weather Patterns Biodiversity Loss, Predator-prey Altitude, Temperature, Humidity Balance, Habitat and Feeding Soil and Vegetation Type Preferences or Requirements Animal- Environment Interface: Expansion/ Loss of Range Invasive Species Environmental Ef fect on Immunity Ef fect of Environmental Conditions on Lifespan and Reproduc tion (especially vectors)
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From page 80... ...
Most recent growth in intensive agriculture and projected growth for the next 30 years is mostly in the developing world, where intensive food-animal production facilities are being set up. These facilities are almost entirely based on feed grain, and in Asia, feed grain is imported from other parts of the world (see discussion later in this chapter on Global Food Systems and Food Safety)
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From page 81... ...
This strong expansion and resulting concentration of meat and milk production in the developing world has consequences for global human and animal health, which is explored in more detail later in this chapter. The shift of production to the developing world transfers the industry to a region with generally weak public services and regulatory oversight 2 The underlying quantitative parameters driving this growth over the period 1992–2002 are (1)
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From page 82... ...
are caused by influences of human intervention, their adjustments or maintenance are not necessarily under human control, and could lead to higher levels of disease risk. But at the same time, the level of risk could be reduced through more intensively managed and maintained factors with respect to animal health and well-being.
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From page 83... ...
The UN's medium variant forecast, based on the assumption of continued fertility declines in lowincome countries, shows the world population continuing to increase to slightly more than 9 billion by 2050. Year FIGURE 3-3 World population projections, median variant forecasts.
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From page 84... ...
. Population Mobility Once a zoonotic disease has emerged, its spread in the human population is likely to be facilitated by population movements.
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From page 85... ...
at risk of contracting communicable diseases when visiting tropical coun tries, but they also can act as vectors for delivering infectious diseases to a different region or potentially around the world, as in the case of SARS. Refugees have become impoverished and more exposed to a wide range of health risks because of their status (Toole and Waldman, 1997)
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From page 86... ...
The combination of reduced population increments and declining rural populations is likely to increase pressures on land resources in the future. Human Behavior and Cultural Factors Researchers have identified several social and cultural factors as drivers of emerging zoonotic diseases (Mayer, 2000; Patz et al., 2000; Daszak et al., 2001; Macpherson, 2005)
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From page 87... ...
Challenges to disease surveillance include not only heavy human and animal traffic and crowded conditions in ports and pilgrimage sites, but also political instability in the region and lack of cooperation among countries, which undermines the reporting of sick animals. Food Preferences Taste is a cultural phenomenon that influences food preparation and is also a driver of zoonotic disease transmission and infection.
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From page 88... ...
Consumer preference for fresh products of wet markets is a complicating factor for health authorities that are trying to reduce health risks. Bushmeat consumption, especially of primates, has been tied to zoonotic diseases such as HIV and Ebola (Peeters et al., 2002; Chapman et al., 2005; Daszak, 2006)
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From page 89... ...
. Companion Animals The popularity of companion animals is a cultural phenomenon subject to social and economic contingencies.
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From page 90... ...
. Global Food Systems and Food Safety The livestock production system,5 farm and market structure, and farm geography are major variables that define the emergence and consecutive spread of a zoonotic disease.
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From page 91... ...
and services (e.g., animal health and expert advice)
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From page 92... ...
. These trends have major implications for the emergence of zoonotic diseases.
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From page 93... ...
This was a core technology that was adopted to create the first fully vertically integrated approach (seeds for animal feed, and animals purposed for fast food)
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From page 94... ...
Number per square km <1 10–20 100–250 International Boundary 1–5 20–50 >250 Water 5–10 50–100 Unsuitable for ruminant FIGURE 3-6 Global swine distribution.
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From page 95... ...
, acting through the World Trade Organization, deals almost entirely with a series of diseases listed as "notifiable," which are of importance to agriculture and trade. High-impact diseases that are present in introduced wildlife and that do not affect human or food-animal health are rarely the subject of legislation, even though OIE has the authority to list wildlife diseases as notifiable due to their impact on wildlife and the environment.
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From page 96... ...
Fish and Wildlife Service (USFWS) conserves, protects, and enhances fish, wildlife, and plants and their habitats and is responsible for ensuring that imports meet international CITES (The World Conservation Union's Convention on International Trade in Endangered Species of Wild Fauna and Flora)
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From page 97... ...
. ENVIRONMENTAL FACTORS Emerging infectious diseases are by definition in a process of flux, either rising in incidence, expanding in host or geographic range, or changing in pathogenicity, virulence, or some other factor.
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From page 98... ...
Human migrations also drive land-use changes that, in turn, drive infectious disease emergence. Habitat Fragmentation One of the key products of anthropogenic land-use change is the fragmentation of wildlife habitat, which alters the composition of host species in an environment and the fundamental ecology of microorganisms.
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From page 99... ...
Smaller fragments in North American forests have fewer small mammal predators and higher densities of white-footed mice, a highly competent reservoir of the Lyme disease pathogen Borrelia burgdorferi (Ostfeld and Keesing, 2000)
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From page 100... ...
Human encroachment on wildlife habitat has broadened the interface between wildlife and humans, resulting in increased opportunities for both the emergence of novel or reemergence of known infectious diseases in wildlife and their transmission to people. Rabies is an example of a zoonotic disease carried by animals that has become habituated to urban environments.
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From page 101... ...
Although it is not a direct driver of disease emergence, differences in laboratory diagnostic approaches and diagnostic goals between the human and animal health fields, variable levels of communication, and limited comparison of microbial populations in humans and animals can hinder early recognition of an emerging zoonotic disease event. These factors can delay intervention and response with consequent amplification of the impact in both human and animal populations.
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From page 102... ...
Early recognition and intervention in an emerging infectious zoonotic disease event is essential to limit spread, whether it involves a novel agent such as the SARS virus or an adaptation of a routinely recognized pathogen such as influenza virus. Limitations in conventional approaches to diagnosis of infectious diseases in humans and animals, while not directly driving emerging disease events, can contribute to spread within the population.
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From page 103... ...
through vaccination of all at-risk animals, in practice, food-animals are only vaccinated against diseases as a matter of cost–benefit if there is a concern regarding the health of the herd or a high probability of human health risk. Although the topic of antibiotic resistance is beyond the charge of the committee and is in itself the topic of other major studies, the committee recognized the importance of the issue to make a few observations.
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From page 104... ...
evaluated the air plume downwind from a CAFO and found a greater concentration of antibiotic-resistant bacteria within and downwind of the swine facility than upwind. Some reports have postulated an association between human and animal health, food-animal antibiotic resistance, and antibiotic resistance in clinical isolates (Teuber, 2001; Smith et al., 2002)
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From page 105... ...
. Laboratory Animals or Biological Agents in Research As biotechnology grows and studies in animals continue, there is always the possibility of zoonotic disease occurring in the scientific staff who are responsible for the care of the animals, or in laboratory workers engaged in microbiological aspects of the disease.
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From page 106... ...
The most effective way to prevent zoonotic disease threats is to bring the various drivers of such threats under better control. However, increasing fears of zoonotic disease emergence and spread underscore the lack of confidence in the legal, regulatory, and enforcement mechanisms established by nations to address the political, economic, and cultural trends that exacerbate zoonotic threats.
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From page 107... ...
The committee also concludes that dedicated attention and resources to improve our recognition of and comprehension about these factors is a significantly noticeable gap in global zoonotic disease surveillance, reporting, and response efforts. REFERENCES Adeola, M
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From page 108... ...
1998. Preventing emerging infectious diseases: A strategy for the 21st century.
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From page 109... ...
2000. Emerging infectious diseases of wild life -- Threats to biodiversity and human health.
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From page 110... ...
Presentation, Fifth Committee Meeting on Achieving Sustainable Global Capacity for Surveillance and Response to Emerging Diseases of Zoonotic Origin, Washington, DC, December 1–2.
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2003. The ecology of infectious disease: Effects of host diversity and community composition on Lyme disease risk.
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From page 112... ...
2000. Geography, ecology and emerging infectious diseases.
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From page 113... ...
2004. Ecological sources of zoonotic diseases.
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From page 114... ...
Emerg Infect Dis 11(12)
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