I think my dog has heartworm. He's having trouble breathing and gets lethargic in the middle of our daily walks. How can I tell if he's infected, and can he give heartworm to my cat?
—Jaik
There are many different conditions that could cause the symptoms your dog is experiencing, Jaik. Heartworm disease is just one possibility. You should have him examined by your veterinarian to diagnose the problem. Heartworm can be diagnosed by a fairly simple blood test, but your veterinarian may have to perform other diagnostic tests, including a chest X-ray, to determine the source and severity of the problem. Cats can get heartworm, too, but the disease is spread by mosquitoes and would not be passed directly from your dog to your cat.