Eliminating malaria may or may not be possible. If you look at the work that Jimmy Carter and others have done to eradicate Guinea Worm -- reaching a low of 148 people infected in 2013, down from 3.5e6 in 2013 -- it is now primarily a political problem. The last infections are in south Sudan. If Gates can accomplish this, eradicating malaria is a worthy coda of a life.
And on the other side, the fake vaccine drive used to locate Osama bin Laden (or at least the leaking of it) might turn out to dwarf the September 11th attacks--it may keep polio from being eradicated. Hopefully it just delays the eradication. Back on topic: how does Gates want to address animal vectors for malaria? Nothing in the blog post.
Some charities (like MSF) are incredibly anti-political for exactly this reason. Some charities (like US AID) are not/