posted on Apr, 20 2010 @ 04:58 PM
Go take a look at the life cycle of toxoplasma.
It has a one-shot reproduction cycle in cats. Once a cat has served as a host, they usually can't do so again due to the cat's immune system. So
toxoplasma has to hunt down cats to infect.
It jumps to other hosts to do so, in which it can't reproduce. Like a rat or mouse. Once a rat is infected with toxoplasma, cats become attractive to
it. It loses all fear of cats, and seeks them out. The cat eats them, and is infected with the toxoplasma.
It also infects old ladies, and turns a percentage of them into cat ladies, who hoard cats, providing a rich growth medium for it.
There are other parasites and bacteria that do this in animals.
[edit on 20-4-2010 by Bedlam]