Health09 Feb 2011 04:50 pm
A zoonosis is any infectious disease that can be transmitted from non-human animals (both wild and domestic) to humans, or from humans to non-human animals (the latter is sometimes called reverse zoonosis or anthroponosis). Zoonotic diseases are anything but rare: of the 1415 pathogens known to affect humans, 61% are zoonotic, and have been with us since early historical times- there are biblical references to plague, a bacterial zoonosis mainly transmitted to humans by fleas; and some historians contend that a disease first described by Thucydides during the Plague of Athens (430–425 B.C.E.) was typhus, a louse-borne zoonosis.
In fact, many modern diseases, even epidemic diseases, started out as zoonotic diseases. It is hard to be certain which diseases jumped from other animals to humans, but there is good evidence that measles, smallpox, influenza, HIV, and diphtheria came to us this way. The common cold, and tuberculosis may also have started in other species. Other examples of zoonoses include rabies (a viral disease that can be transmitted to humans through an infected animal’s bite) and psittacosis (a chlamydial infection resembling influenza that is spread to humans by the droppings of infected birds).
The major factor contributing to the appearance of new zoonotic pathogens in human populations is increased contact between humans and wildlife. This can be caused either by encroachment of human activity into wilderness areas or by movement of wild animals into areas of human activity due to anthropological or environmental disturbances. Other risk factors may include: (1) alteration of the environment, affecting the size and distribution of certain animal species, vectors, and transmitters of infectious agents to humans; (2) industrialization of foods of animal origin—that is, changes in food processing and consumer nutritional habits; (3) increasing movements of people, as well as an increased trade in animals and animal products; and (4) decreasing surveillance and control of some of the major zoonoses.
I hate to be the bearer of bad news, but zoonotic diseases aren’t disappearing anytime soon. In fact, there has been a disturbing reemergence of previously recognized zoonoses that were believed to be under control. To make matters worse, a number of deadly new zoonotic diseases have emerged in recent history, most notably HIV/AIDS, which arose from nonhuman primates, and at some point “jumped” to humans. In fact, scientists agree that the greatest potential threat posed by zoonotic diseases is the hidden potential of what uber diseases might arise in the future.
Christ on Crutches! What disease could possibly be worse than the HIV/AIDS pandemic?!? My imagination fails me.
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