Asia, my sweet-tempered golden retriever mix, had a rough start in life. She was abandoned when she was just a year old and spent the next two years living outdoors. By the time she was rescued, she had picked up a potentially fatal souvenir of her ordeal: heartworm. Thankfully, the problem was caught in time and treated, and Asia now has been declared heartworm-free. Ideally, however, she would never have had it in the first place. The disease can be avoided with a few basic precautions.
Be aware of the risk
Heartworm is exactly what it sounds like: Worms, which can grow to 14 inches long, take up residence in an animal's heart and pulmonary arteries, damaging the heart and lungs and restricting blood flow. The disease is transmitted by mosquitoes, which deposit heartworm larvae under the skin as they bite. According to Allan Paul, chair of parasitology at the University of Illinois College of Veterinary Medicine, heartworm is well-established "along rivers because of the high mosquito populations." Incidents of the disease are highest in the southeastern states, along the Mississippi River basin, and into Illinois and Indiana, but anywhere there are mosquitoes, there is a risk of heartworm.
Focus on prevention
Heartworm is far easier to avoid than to cure. Fortunately, the cost of preventive medicine isn't prohibitive, running from $35 to $150 a year, depending on the pet's size and the brand of medication. "All dogs should be on heartworm preventative," says veterinary cardiologist Jennifer Sidley of Chesapeake Veterinary Cardiology Associates in Vienna, Va.
Ask your vet about different medicines, which include a chewable that protects against several parasites and a topical medicine that also kills fleas, ticks and ear mites. Whichever one you choose, it's vital to administer it on time. And regular testing is a must: John McCall, vice president of the American Heartworm Society, recommends annual screening, especially in regions where heartworm is prevalent.
Identify susceptible pets
Though heartworm most often affects dogs, ferrets and cats also can contract the disease. Diagnosis is more difficult and treatment much riskier for these animals than it is for pups, making preventive medicine all the more important. Even one dead heartworm in a cat's tiny lung "can block all blood going to a fraction of the lung," gravely endangering the animal, Sidley says.
Watch for symptoms
Dogs may exhibit chronic coughing, shortness of breath, lethargy and a low tolerance for exercise; coughing, breathing problems and unexplained vomiting are possible signs in cats. In the early stages of infection, however, visible symptoms are unlikely. More advanced cases may involve fainting, spitting up blood or swelling of the abdomen, indicating congestive heart failure. Blood tests and X-rays are usually sufficient to diagnose heartworm in dogs, though occasionally ultrasound or an EKG may be required to determine the severity of the infection.
Understand the treatment
The American Heartworm Society recommends treating infected dogs with a three-injection series of Immiticide, a course that can cost $400 to $1,000. After the first dose, the dog must be kept very calm for at least a month -- too much activity can push the dead heartworms toward the lungs before they've broken down, causing potentially fatal blockages. The next two injections are administered 24 hours apart, requiring an overnight hospital stay and an additional four to six weeks of restricted activity. Six months after the completion of treatment, a heartworm test will tell whether it was successful.