East Lincoln Animal Hospital

7555 Highway 73 East
Denver, NC 28037



Heartworms and Cats

No Description resized to 300 pixels wideReports vary but from 5 % to 15.9 % of cats may be affected by heartworm disease.

Heartworm disease in cats is different than heartworm disease in dogs. Cats are more resistant to heartworm infections than dogs are and rarely have microfilariae (baby heartworms) circulating in their bloodstream. Cats usually have fewer and smaller worms than dogs and the heartworm has a shorter lifespan in the cat (2 years) compared to the dog (5 to 7 years).

When a cat is bitten by a mosquito carrying the larval stage of a heartworm, it takes approximately 8 months before the heartworm larvae develops into a sexually mature adult. The heartworm larva travels or migrates from the point where it enters the body (the bite site) through the tissues of the body and to small arteries and blood vessels in the lungs.

Heartworms cause damage when they enter a blood vessel and go to the pulmonary arteries in the cat.  A new term, Heartworm Associated Respiratory Disease (HARD), has been used to describe this damage. The symptoms caused by the heartworm infection at this stage are often misdiagnosed as asthma and allergic bronchitis.  A heartworm in a cat does not even have to be a mature adult before it starts causing disease!  A sudden shock like lung condition caused by the death of heartworms in cat may also occur and can often lead to the death of the cat.

Symptoms of Heartworm Disease in cats (may include one symptom or multiple symptoms):

     asthma or bronchitis
     vomiting (not associated with eating)
     dyspnea (difficulty breathing)
     loss of appetite
     weight loss
     chylothorax (white fluid in lungs)
     fast heart rate
     neurologic disease
     sudden death

Diagnosis of Heartworm Disease in cats

The diagnosis of heartworm disease in cats can be difficult.  A negative heartworm test does not rule out an infection. The heartworm antigen tests are checking for female worms and some cats will only have infections with male worms (and show up negative on the test). Some cats may only be infected with one heartworm and this may not be enough antigen to cause a heartworm test to show positive.

A diagnosis of heartworm disease may require antigen and antibody testing, chest x-rays, ultrasound examination of the heart and lungs, and necropsy (examination of the heart and lungs after death).

Treatment of Heartworm Disease in cats

There is no medication available to "cure" a cat with heartworm disease.  Cats that have lung disease caused by the heartworms are often treated with steroids to decrease the inflammation in the lungs.  Cats with severe symptoms caused by the heartworm disease may require hospitalization, oxygen, bronchodilators, and other treatments to get them through a crisis.

Prevention of Heartworm Disease in cats

Prevention is the best option for cats since there is no cure for heartworm disease.  There are currently four heartworm disease preventive products approved by the FDA for cats:

Heartgard® for Cats (chewable tablet) from Merial
Interceptor® (chewable tablet) from Novartis
Revolution® (topical treatment) from Pfizer
Advantage Multi for Cats (topical treatment) from Bayer

All of the preventative products are given once a month (all year round in NC).

Read or download the files below for more information about heartworm disease in cats!

File NameDescription / Comment
Feline Heartworm Disease FactsRead about the facts in heartworm disease of cats.
Five Myths of Heartworm Disease in CatsRead about the myths in heartworm disease of cats.
HARD in CatsRead about Heartworm Associated Respiratory Disease of cats.
Heartworm Life Cycle in Cats DiagramOpen to view a diagram of the life cycle of the heartworm in the cat.
Map of Incidence of Heartworm disease in catsSee a map of the cases of Heartworm Disease in cats in the USA in 2005.