[HumanHater]

Well all these species probably has role in horizontal gene transfer. They also help keeping animal population from growing too big. However it is very unlikely that any of this factors has any global effect. Some areas of the world don't have mosquitoes or ticks, in others they were eradicated with DDT and other chemicals. Observed negative consequences didn't have anything to do with eliminated targets.

It's possible that in some local areas some animals would be severely affected. But even in that case climate change already changing natural balance. For example ticks are almost culling deers. It is better to find new equilibrium while humanity still can have some control over the ecosystem.