> I know. But when you remove mosquitoes from the picture, aren't you putting selection pressure on the diseases to be airborne?

Organisms also need the opportunity to evolve; removing their only vector is analogous to trying to apply selective pressure to pigs to evolve to fly by throwing them off a cliff. Yes, any pig who could fly would survive and have a huge advantage over all the now-dead non-flying pigs. But it just ain't gonna happen.