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What is Heartworm Associated Respiratory Disease?

Heartworm Associated Respiratory Disease (HARD) is a lung condition in cats caused by the presence of heartworms in either the adult or larval stages.  Adult worms often settle in in the blood vessels of the infected cat’s lungs, and worm larvae can cause an inflammatory response in the airways and lung tissue.  An unsuccessful infection where a parasite does not make it to the adult stage in a cat is common and can still have severe impacts on the feline’s respiratory tract, and he or she is likely to suffer.dogs vs cats - heartwormsHeartworm disease in cats is very different than heartworm disease in dogs.  Cats are an atypical host for heartworms, meaning that most worms cannot live to the adult stage in a feline’s body.  Cats often are undiagnosed due to the fact that the symptoms usually go unnoticed. There are typically only one to three worms in cats, whereas dogs can have hundreds! Even one to three worms can cause severe damage and cause Heartworm Associated Respiratory Disease. To learn more about HARD and other worms in cats, check out the confirm the worm.

How to recognize and diagnose

Cats do not always show symptoms of heartworm, however, common signs of the disease include coughing, open mouth breathing, labored breathing, vomiting, and diarrhea.  Lethargy, rapid heart rate, decreased appetite, and weight loss are also signs to look for.  In severe cases, blindness, collapse, convulsions, and sudden death may occur.  These signs and symptoms of HARD can be confused for other illnesses so it is important to take your cat into the vet if you notice any strange or concerning behavior.

heartworm in catsConfirming a HARD diagnosis is not easy.  Routine tests such as the heartworm antibody and antigen tests, a blood count, chest X-ray, and an ultrasound are often performed to diagnosis HARD and the presence of heartworms.  An X-ray may be able to determine the stage of infection and the severity of damage, and an ultrasound may show the presence of worms and any changes to the heart or lung function.

No cure? So what can I do?

Unfortunately there is no safe or effective treatment of heartworm in cats.  Since there are no approved medications, cats that develop a heartworm infection can only be managed over time.  That being said, this disease is often assumed to be fatal.  This is not true!  Veterinarians are starting to recognize that HARD is actually rarely a fatal disease.  Instead of thinking life-or-death, change your mindset to quality-of-life.


Since there is no treatment for heartworm in cats, we cannot stress how important prevention is in cats!  This entails the year round use of heartworm control products, and following the directions from your veterinarian precisely.