But if the stuff spreads from infected people, to the mosquitos, and back to other critters, and it does, it can spread in many ways besides just birds.
I happen to like wetlands- they increase our beef production and we have healthier, faster-growing cattle- so I am not for draining them except as a temporary, one-year plan. But next spring may be a good time to temporarily hit wetlands with DDT. Skeeters will be killed out over the winter so that route of transmission will effectively be nullified over the winter, and a spraying program in spring should knock its spread next summer. On the other hand, elephant mosquitos are natural predators of the common skeeter in wetlands- they do quite a good job and small minnows do a fine job if they're not all poisoned.
Swamps are the least of our problems- the bulk of the mosquito problem is from local small sources which don't have predatory insects to curb the skeeter larvae. People leave pots and cans and old tires all around an in these mosquitos can breed like crazy free of all predators. My dumbarse neighbor left his pool uncared for all year and the skeeter problem was attrocious- we couldn't figure out where they were all coming from until we went to pick up something that fell in his yard. It was awful... the little jerk won't do anything about it either though we gave him a chance.
I ended up stocking his pool with guppies. Seems to have worked- no more skeeters. Can't wait for him to spot all of the fish.