We do know the consequences. Wealthier nations have essentially eliminated 99%+ of the population of the few species of disease carrying mosquitoes in many broad areas. The effect on the ecosystem was not noticeable. Using cheaper methods to help poorer areas will save 10's of millions of lives and eliminate billions of cases of disease. It's overwhelmingly worth it even if it caused ecological harm. To not do this is, to even fight against doing it is, IMO, immoral.