Malaria is a serious economic drain on endemic countries. It's likely that without this disease burden, living conditions would improve, and the birth rate would go down in these places.

Also, I've had dengue fever, a relatively mild case that laid me up for a week and left my digestive system complaining for months. If I get it again, odds are it will be worse. I say that this is an experiment worth trying; it's not like mosquitoes can't be re-introduced into the wild if somehow necessary.