Heartworm Disease

What happens if my pet is positive for heartworms?

Treatment options for heartworm disease vary greatly from patient to patient.

Dogs

For dogs, the course of treatment varies depending upon how far the infection has advanced and the severity of the damage done. Prospective patients are given a thorough physical, including x-rays and a complete blood panel. These tests allow us to assess the pet's physical condition, which may include enlargement of the heart, damage to the lungs or other internal organs, fluid in the chest or abdomen, and any imbalances in the normal blood chemical levels. Depending upon these findings, a course of treatment will be recommended.

Treatment consists of a series of injections designed to kill the adult heartworms while reducing the damage to the patient. The interval between injections can vary greatly from patient to patient. The pet must be kept quiet and confined during the treatment as the adult heartworms die and detach from the heart. If a pet is active, the potential for a blood clot from a dead heartworm is more pronounced.

Once the course of treatment is finished, the dog is placed back on heartworm preventative and retested in 2 to 3 months to ensure that all adult heartworms were removed.

Occasionally, the decision is made to not treat a heartworm-positive patient. If possible, we will continue or start the patient on heartworm preventative. We do this to prevent the pet from getting any new adult worms, as the preventatives work by killing the larval stages and breaking the life cycle. We do not take this step without first considering the general health of the pet and the advancement of the disease.

Cats

For cats, there is currently no safe cure for heartworm disease.

Since the discovery of heartworm disease in cats is relatively recent, protocols are still being established for the diagnosis and treatment of this condition for our feline friends.

Unfortunately, because cats are not the main host, clinical signs, if they are present at all, may vary widely or be much milder than clinical signs in dogs.

Due to their resistance to the parasite and the much smaller numbers of parasites typically present when a feline is infected, cats have some natural advantages to help them battle this disease. They have even been known to spontaneously rid themselves of a heartworm infestation, seemingly by "hyperactivating" their body's immune response. However, it is unclear if this is the cause of death for the heartworms, or merely a reaction of the host to the death of the parasites.

A heartworm's life span is much shorter in a cat than in a dog, and the time it takes them to mature in a feline host is longer than when they are in a canine host. Cats are more likely to have a single-sex infection, which obviously prevents the production of new heartworms to infect the current host or to be passed on to other animals.

This also has the effect of making heartworms difficult to detect in feline patients. The antigen tests that were developed for dogs, are highly inaccurate where cats are concerned. The antibody tests developed specifically for cats are more accurate, but may still register positive because they are not testing for the presence of the parasite itself, merely the body's reaction to it.

With cats that are positive for heartworm disease, we use supportive therapy, typically when there is evidence of lung or cardiovascular damage caused by the heartworms. The thought is to help them live through the infection until the worms die off.

The treatments currently available for dogs have fatal side effects in nearly 1/3 of feline patients in which they have been tested. As stated, there is currently no approved cure for heartworm disease in cats.

Prevention of the disease with the administration of a monthly preventative is recommended in all cats in high-risk areas such as Redding.