How Ecosystem Disturbance Affects The Spread of Disease
When habitats are damaged, the equilibrium between predator and prey or host and parasite can shift in various ways, sometimes with disastrous consequences:
#1 - Disease Behavior May Change.
* A parasite may switch to a different host, possibly human, when biodiversity is reduced and its natural hosts become rare or nonexistent: a parasitic disease, leishmaniasis, has become far more common in the developing world. When rain forest is cleared, or roads or dams built, rodents--the traditional host for the sandflies that transmit the parasite--are displaced. The insects bite available humans instead.
* When people move into a previously untouched habitat, diseases naturally occurring in wildlife may adapt to be able to infect humans directly: the virus that causes AIDS probably switched over to humans from an endangered subspecies of chimpanzee when hunters entered the apes’ West-Central-African jungle habitat and came into contact with their blood.
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