There is a joke amung Wisconsinites that our state bird is the mosquito, because there are so many here, it is nuts. Even our backyard is loaded with them, you look out the window and you can see little clouds of mosquitos above the grass.

There are no vaccines for dogs and cats that I am aware of, but I read in a different article that they are trying to make vaccines for dogs and cats.
"There may be other dogs that have been exposed," Veterinary Diagnostic Laboratory at the University of Illinois Director John Andrews told a USA Today reporter.

There is a West Nile vaccine, but it has been approved for use only in horses. Vaccines for dogs and cats are currently being developed.
I am sure rats and cats can get it too, that is why I am cautious with my ratties and kitties. Birds, horses, squirrels, and dogs have been shown to have it- so I am sure it can affect cats and rats. I just like to play it safe.

In fact, I just found proof that cats can get West Nile Virus:


Q. How do cats and dogs become infected with West Nile virus?
A. Dogs and cats become infected when bitten by an infected mosquito. There is also evidence that cats can become infected with the virus after eating experimentally infected mice.