5:00 Dose of EIDology: What do Animals Have to do With It?

It starts with a tale called host adaptation.

Pathogens, especially the ones that exclusively rely on their hosts for survival, are not inherently mean-spirited.  Though this may seem counterintuitive at first, parasitic pathogens adapt to, and co-evolve with, their hosts to minimize disease.  If you think about it, if you need to infect a living thing to survive, killing everything in your path doesn't make much sense.  Talk about burning your own house down!  Parasitic pathogens, then, have a vested interest in adapting to a particular host and perfecting that relationship.  


What does this have to do with emerging diseases?  You guessed it.  An emerging disease-causing agent has found its way into an alternative host.  Most of the time nothing happens when a well-adapted pathogen infects the wrong host.  For those rare instances when something happens, however, it tends to be very dramatic.  For humans, the source of our "maladapted" pathogens that cause emerging diseases are animals, be they livestock or wildlife.  They haven't learned how not to kill a human host, for lack of a better way of putting it.  Of course, there is of course a second side of the story on the human front...but I'll leave that to the immunologists to discuss.