PARASITOID
A parasitoid is an organism that spends a significant portion of its life history attached to or within a single host organism in a relationship that is in essence parasitic; unlike a true parasite, however, it ultimately sterilises or kills, and sometimes consumes, the host. Thus parasitoids are similar to typical parasites except in the more dire prognosis for the host.
Sounds exactly correct. And, in the event that moslems did conquer the world (I am 100% sure they will not), they would kill each other to death mostly, and in a few hundreds years there would be a few random groups of hunter gatherer tribes left, wandering among the increasingly overgrown ruins.