What is Heartworm?
Heartworm disease is a serious and potentially fatal condition caused by parasitic worms living in the arteries of the lungs and occasionally in the right side of the heart of dogs, cats and other species of mammals. The disease is spread by mosquitoes that become infected with microfilariae while taking a blood meal from an infected dog. When a animal is infected it takes about 2 months for the larvae to migrate through the connective tissue, under the skin, then pass into the animal’s venous blood stream and they are then quickly transported to the arteries of the lung. It takes a total of approximately six months for the infective larvae to mature into adult worms that begin producing offspring, microfilariae. Adult heartworms can live for five to seven years in the dog.
Symptoms of Heartworm
In the early stages of an infection there is usually no abnormal behavior. As the infection grows, the animal will develop a cough, have unusual sounding lungs, and decrease their amount of exercise. As the heartworm becomes severe the animal may have trouble breathing, due to inflammation of the Pulmonary arteries, fluid may accumulate in the abdominal cavity, and the heart may sound abnormal. As the worms increase in numbers they back up into the right heart and even vessels leading to the heart (Vena Cavae) at this point the animal is severely debilitated and near death.
Treatment
The treatment for heartworm disease is currently only approved for use in dogs. There is no protocol for the treatment of cats other than supportive care. Cats may be prescribed bronchodilators and corticosteroids to control symptoms. The only drug approved is called melarsomine. It is an organically bound arsenical compound that is given by injection in the lumbar muscles of the back. One injection is administered, followed by a second one 24 hours later if the patient tolerates the medication well. In a split treatment, the dog is given the first injection followed by the series of two injections 4 to 6 weeks later. In either case, the dog must be kept confined for several weeks after the injections to avoid complications from treatment, Pulmonary Thromoemboli from dead worms and blood clots.
Prevention is the best way to avoid heartworm disease and the risk involved with treatment (not to mention the expense). There are a number of safe heartworm preventive medications that your veterinarian can prescribe for your pet.