Treatment Options

Treating heartworm disease can be difficult and dangerous. The therapeutic goals are to kill all adult worms and kill all microfilaria that are present in the dog’s bloodstream. Other goals are to resolve any complications that the dog is suffering and to prevent future reinfection. In considering treatment options, owners and veterinarians must pay special attention to potential adverse drug reactions and the possible serious side effects of live or dead adult worms causing pulmonary hypertension, congestive heart failure and/or cardiovascular blockage.

Infected dogs suffering acute respiratory and/or cardiac complications from heartworms will be hospitalized, given oxygen if necessary and placed on strict bed rest. Steroids may be prescribed to reduce inflammation, and aspirin may be given to address or prevent thromboembolisms. There are several medical protocols to eliminate adult heartworms. The dog’s veterinarian is the best person to discuss these options with the dog’s owner and to help her understand the risks, benefits and costs associated with each protocol. That decision will involve consideration of the dog’s age and overall health, the presence of any associated medical complications (such as liver or kidney damage or heart failure), the owner’s financial resources and the owner’s tolerance of treatment regimens. Some heartworm medications contain arsenic and can cause toxic side effects, including vomiting, diarrhea, appetite loss, liver damage, kidney failure and even death. Old dogs are at especially high risk of suffering adverse consequences from drug therapy to eliminate adult heartworms.

There also are surgical procedures designed to remove adult worms lodged in the vena cava and/or the right heart chambers. Surgery involves making an incision in the dog’s neck and passing a tong-like instrument down the jugular vein, through the superior vena cava and directly into the right side of the heart. The surgeon then pulls out the parasites one by one, which requires radiographic instruments and special technical skill. This procedure is usually reserved for very critical cases that do not respond well to medical therapy.

When the immature form of heartworms, microfilaria, are present, additional treatment must be considered. These protocols can cause serious adverse reactions in some dogs, including hypothermia, depression, weakness, vomiting and shock. Most dogs are hospitalized during microfilaricide therapy.

Prognosis

Dogs with heartworm infection often have a good chance for a full recovery, especially if they have few or no symptoms of illness. Dogs with moderate to severe infection accompanied by heart failure, liver disease and/or kidney damage have a fair to guarded prognosis. Unfortunately, dogs with Class 4 disease (caval syndrome) have a poor to grave prognosis, even with treatment.