There are a few things to look for in order to tell the difference between kennel cough and heartworms. Kennel cough is a respiratory illness that typically occurs in dogs and cats, and is typically accompanied by fever, coughing, and difficulty breathing. Heartworms, on the other hand, are a parasitic infection that can be contracted by dogs and cats. They can typically be found in the intestines, and can cause serious health problems. If your dog has kennel cough, you should give him antibiotics to help clear the infection and prevent the spread of the worm. If your dog has heartworms, you should provide him with a heartworm prevention tablet to take before bed to help prevent him from getting infected.