What's the worst that can happen?

  The extermination of sparrows – also known as the Eliminate Sparrows campaign – resulted in severe ecological imbalance, and was one of the causes of the Great Chinese Famine which lasted from 1959 to 1961, with an estimated death toll due to starvation ranging in the tens of millions (15 to 55 million).

Though that's unlikely to follow on from simply reducing mosquitoes in urban areas ... it absolutely warrants a close eye being kept on roll out and knock on effects.