Mosquitoes are not only a nuisance to us, they can be dangerous to our pets. Mosquitoes carry heartworm larva which can be transmitted to your pets. Even if your cat or dog only goes outside to the bathroom, they can still be infected. It only takes one mosquito bite. The larva migrate through the bloodstream to the heart, where they can grow 6 to 14 inches long. Several hundred may be present in the dog. Heartworms can damage lungs, liver, and kidneys in addition to the heart. They can kill your pet! Heartworms have infected all breeds of dogs, large, small, long-hair, short-hair, inside, outside, in all 50 states. They can also infect cats - the presence of just one worm, alive or dead, can cause significant inflammation of the lungs and blood vessels.