Preventing heartworm disease in your pet is inexpensive and the right thing to do. For dogs, the chance of them becoming infected if bitten by a mosquito carrying heartworm is 90%. Once infected, the heartworms take up residence in the right side of the heart, attaching to the interior heart muscle and living off the tissue and blood. They chew on the heart muscle with sharp teeth, impede normal blood flow through the valves with their bodies, and shower the lungs with excrement, offspring, and body parts. Heartworm diease in dogs first develops as a cough from the severe inflammation in the lungs, and progresses to heart failure as the worms continue to grow in size and number.
To stop the progression of disease the heartworms must be killed with an arsenic derivative. The treatment is both expensive and carries a risk proportional to the burden of worms on the heart.
Cats can also become infected with heartworm. The good news is that cats are naturally resistant to heartworm and may not develop an infection if bitten by an infective mosquito. The bad news for cats is that due to their smaller size, a single heartworm in a cat is enough to cause serious illness and death, and there are no current treatment options for cats with heartworm disease. Bottom line; although this disease is rare in cats, it is usually fatal. For this reason veterinarians in areas where heartworm is prevalent recommend heartworm prevention for cats during the mosquito months. Heartworm prevention for cats can be either oral or topical once a month dosing (same products as for dogs above), and also have the added benefit of treating and preventing other parasites. Cats do not require a blood test before starting prevention, and can start right away.