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Christine O'Connor

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Can we control the emergence of zoonotic infectious disease?

Seventy five percent of the world’s emerging infectious diseases are zoonotic, or animal, in origin. Familiar examples include HIV/AIDS, Ebola, SARS, Lyme disease and West Nile Virus.

Humans play a big part in the emergence and spread of these and other infectious diseases. Our ever-expanding encroachment on forests – due to deforestation and increases in bushmeat hunting – increases the potential for disease transmission from animals to humans. Urbanization and global travel more easily allow for the spread of a disease from person to person and across the globe. These factors combine to greatly increase the probability of successful emergence and spread of an infectious disease.

Despite the clear importance understanding and controlling zoonotic diseases we have not had much success eradicating them, or even limiting their spread. It is hard to eradicate what we can’t find. Fore example, despite many years of study, researchers still are not sure where Ebola comes from. Outbreaks can be traced to handling of dead chimpanzees and gorillas, but neither appears to be the reservoir host (a species that is a source of infection but not affected by the disease) for Ebola.

What should be done to stop or control the emergence and spread of these diseases before they become global pandemics? Should we try and limit close contact with wild animals, perhaps via habitat preservation? Should we better control the bushmeat trade and/or educate hunters and consumers of bushmeat and other types of wild animal markets of the risks involved with such meat? Or, is a more proactive approach possible? Is there a way to pre-emptively identify such emerging diseases, via monitoring of wild animals and those who regularly have close contact with them?

Souce: Spillover by David Quammen

Also see: Q&A on swine flue with virus hunter Nathan Wolfe "We've created the perfect storm for viruses" http://blog.ted.com/2009/04/28/qa_with_virus_h/


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    Jun 4 2013: In the United States, we are also seeing an increase in the incidences of some infectious diseases due to our changing interactions with our environment and changing the environment itself. Emerging zoonotic diseases aren’t just a problem in other parts of the world! Lyme disease is a bacterial pathogen that humans get from ticks and which is prevalent in parts of the Midwest and Northeast in the US and its incidence is on the rise. A study by Allen et al. (2003) found that risk of Lyme disease increased in areas of NY state with decreasing forest patch size. This is thought to happen because mice, a reservoir animal for Lyme disease, increase in population density at forest edges. As forest areas become more fragmented and smaller, the amount of area considered an edge increases. Where there are more forest edges there are more mice, and then there are also more ticks feeding on the larger mouse population and potentially becoming carriers for the Lyme disease bacterium and then passing it on to humans via biting.
    These sorts of patches can be created and exacerbated by suburban and exurban development, I believe, where development encroaches on standing forest and people want to have some forest in their backyard, so there is lots of close contact with small patches of forest.

    Allan, B et al. Effects of forest fragmentation on Lyme disease risk. 2003. Conservation Biology 17: 267-272

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