Learned immune deficiency

One approach for parasites seeking to evade the host's immune system is to attack it and disable it. This approach is famously taken by the HIV virus - the virus which produces AIDS. However the result is typically a weakened immune system, and a collection of opportunistic infections that take advantage of the breaches in the host's defenses.

The nearest cultural equivalent to these types of parasite are probably beliefs that compromise critical thinking faculties. Probably the most famous of these is the belief that faith is a virtue. Faith - in the sense of belief without evidence - allows a variety of religious memes to thrive which would ordinarily be eliminated by critical faculties. Such memes benefit by association with the "faith" meme. However, the host of a "faith" infection is left with a weakened memetic immune system. This creates an environment in which a wide variety of other counter-factual beliefs can flourish.

In short, faith is the AIDS of the mind.