Having worked in public health for 22 years and watched and read a lot of science fiction, if one species kills their hosts/food source, they die. Virility... er, virulence, is not what makes a species dominant. It's the ability to outlive the competition, and then keep going... except that's not dominance, that's some other "...ance/...ence". Dominance would be the ability to kick other species' asses (or the figurative equivalent of figurative asses) and make them their bitches. Cockroaches are pretty good at that, and while I'm not sure, I don't think they even try very hard.

It's not about intelligence or skill, but resilience, persistence, and the ability have up to 60 offspring per egg-laying session, with three sessions per mating. If we could have 180 kids every time we had sex... Now that I think about it, 1) if we did that, we probably wouldn't last long as a species; 2) talk shows would get really monotonous; 3) wouldn't "The Roach People" make a great horror novel?