Heartworm Disease: Symptoms and Treatments


Last week we discussed the heartworm life cycle and how disease transmission can occur in dogs and cats. This week, let’s focus on the symptoms and treatment of heartworm disease.


Symptoms: You may not notice any external symptoms of heartworm infection in cats, but if symptoms do occur they can range from cough, asthma-like signs, vomiting, decreased appetite, weight loss, trouble walking, sudden collapse, to death.

Treatment: There are no approved forms of treatment for adult heartworm infections in cats. Heartworm positive cats are stabilized and treated with supportive care measures. Some cats will clear the heartworm infection, but they may be left with long term respiratory damage from the infection.

Prevention: Prevention is key for cats to avoid this terrible disease. Follow the American Heartworm Society’s recommendations for year round heartworm prevention in cats to keep your cat protected!


Symptoms: In the early stages of an infection, a heartworm positve dog may not appear ill. As the disease progresses, symptoms can include cough (mild to severe), exercise intolerance, general fatigue, decreased appetite, and weight loss. Internal changes can include heart and lung changes, heart failure, heart blockage (from worms) resulting in cardiovascular collapse, damage to other internal organs, and even death.

Treatment: Treatment is targeted against the adult heartworms and the microfilaria. Decisions on treatment protocols are based around the severity of the disease. Injections of an arsenic-based compound called melarsomine (Immiticide) is the only approved treatment for adult heartworms in dogs. The injections do not come without risk. Pain and swelling at the injection site, fever, vomiting, and loss of appetite are common side effects. More severe reactions or complications can occur as the dead and dying worms break off. These worm fragments can lodge in the blood vessels creating life threatening situations.

While a dog is undergoing treatment for heartworms, the dog’s activity must be severely restricted. This is because physical activity could cause the dying worms to create more damage to the heart and lungs.

Prevention: Prevention is key for dogs to avoid this terrible disease. Follow the American Heartworm Society’s recommendations for year round heartworm prevention in dogs to keep your dog protected!

Author: Dr. C. Noureddine, DVM, MS