UF veterinarians offer alternative for heartworm treatment

With the only FDA-approved treatment for heartworm disease currently unavailable on the market, University of Florida veterinary cardiologists say practitioners should be aware of existing guidelines for treating affected dogs, and that UF offers an alternative treatment — surgical extraction of the worms — that may benefit certain animals.

“This disease can be prevented with monthly heartworm medications, but now treatments for affected dogs are limited,” said Herb Maisenbacher, V.M.D., a clinical assistant professor in cardiology at UF’s College of Veterinary Medicine. “The American Heartworm Society has released urgent guidelines for veterinarians to manage dogs with this disease during the drug shortage.”

The drug used for heartworm treatment, known by its trade name, Immiticide, is unavailable to veterinary practitioners because of manufacturing issues.

The AHS guidelines include administration of monthly heartworm preventive and four-week courses of an antibiotic called doxycycline repeated quarterly for one year. In addition, therapy for symptoms of the disease, such as coughing or difficulty breathing, may be prescribed, Maisenbacher said.

“Lastly, heartworm-infected dogs should be restricted from exercise, as activity can worsen the damage and symptoms caused by the heartworms,” he said.

The goals of the AHS guidelines are to maintain the dog’s health, reduce any damage caused by the heartworms and prevent additional heartworm transmission.

“Although the treatment may shorten the lifespan of adult heartworms, dogs will still likely remain heartworm positive,” Maisenbacher said. “However, once Immiticide becomes available again, dogs treated under the AHS protocol should be retested for heartworms and, if positive, treated appropriately with the drug.”

Dogs with extensive disease may benefit from an option available at the UF Small Animal Hospital, where veterinary cardiologists surgically extract heartworms from dogs using specialized instruments that can be inserted into the right side of the heart and pulmonary arteries through the jugular vein on the side of the neck.

“This minimally invasive technique is deemed most valuable as an option for dogs with considerable symptoms or high levels of heartworms,” Maisenbacher said. “In this way, the heartworms are physically removed from the dog instead of just waiting for the worms to die.

“The procedure is not risk-free, as it involves heavy sedation or general anesthesia, and is not inexpensive,” he said. “But for dogs with extensive disease, it could be another option to consider at a time when there is no other available treatment.”

Heartworm disease is transmitted from dog-to-dog by mosquitoes. Heartworm larvae enter the dog through the mosquito’s bite and can grow into worms up to 12 inches long. These worms reside in the pulmonary arteries, blood vessels that take blood to the lungs, and sometimes in the right side of the heart. They can live for up to seven years while causing damage to blood vessels, to the lungs themselves, and to the heart.

Heartworm disease can cause dogs to cough, cough up blood, be lethargic, lose weight and have difficulty breathing. Other signs include fainting, abdominal distension and even death.

More information about heartworm disease or the current AHS guidelines can be found at www.heartwormsociety.org. To reach UF’s veterinary cardiology service, please call the UF Small Animal Hospital at 352-392-2235.