Animal Care Associates, Inc
840 Oakwood Road
Charleston, WV 25314
304-344-2244

Heartworm Infection in Dogs and Cats

Heartworm infection and disease are preventable. Have your pet checked for heartworms annually, and keep your pet on monthly heartworm prevention.

What type of pet is most susceptible to heartworms?
Dogs get heartworms much more commonly than cats, although the incidence of heartworms in cats is higher than once thought. Breed, sex and age do not affect your pet’s susceptibility to heartworms. Outdoor pets come into contact with mosquitoes more frequently than indoor pets and may be at increased risk for heartworm infection. The disease is found in virtually all parts of the United States and Canada.

How can I prevent heartworm disease in my pet?
Highly effective preventative medications are available for dogs and cats. These medications are prescribed for pets that are not infected with heartworms or that have been successfully treated for heartworms in the past. Your veterinarian will test your pet for the presence of heartworms before prescribing medication.

If you live in a known heartworm area, or if your pet is traveling with you to a known heartworm area, you veterinarian may prescribe preventive medications. If your pet becomes infected, these medications will prevent heartworm larvae from developing into adult heartworms. It is crucial to administer all prescribed medications as directed.

As a safeguard, your veterinarian may recommend annual screening tests, even for pets that are on heartworm preventative medicine.

What physical signs might my pet show when infected with heartworms? Several signs might indicate the presence of heartworms in your pet. Talk to your veterinarian right away if your pet shows the following physical signs: -Sudden weight loss -Difficulty breathing -Soft, persistent cough -Tires easily -Listlessness or weakness Many of these signs are most noticeable after exercise. Heartworms clog the heart and/ or the main blood vessels, reducing the blood supply to or from other organs such as the lungs and liver. Major bodily functions, including breathing, are affected.

Image from:  http://sg.merial.com/pet_owners/dogs/canine_heartworm.asp

How is heartworm disease treated?
Your veterinarian will require a blood sample to determine the presence of heartworms. Additional tests may be necessary to confirm the presence of heartworms. Once the presence of heartworms has been confirmed, diagnostic tests may be required to determine whether or not your pet can tolerate heartworm treatment. These tests include, but are not limited to, blood-chemistry panels, radiographs (X-rays), and electrocardiograms.

Dogs

You veterinarian will recommend the safest and most effective treatment protocol, which will depend on the severity of the disease and the results of diagnostic testing. Today, more than 95 percent of dogs with heartworm disease are treated successfully. Most are cured with the help of medications, and the rare case requires surgery. In any case, early detection and ongoing prevention prevent needless suffering.

If your dog’s heartworm infection is not too severe, the veterinarian will administer a drug to kill the adult heartworms. Complete rest is essential foe the month following treatment because pieces of the dead, decomposing heartworms circulate through the blood and into the lungs during this time. Eventually the pieces are reabsorbed into the body, but is they are dislodged during this time, your dog may suffer heart or respiratory failure.

In addition to the adult heartworms, there may also be microfilariae ( heartworm offspring) in your pet’s blood. Your veterinarian will recommend a treatment protocol to kill them as well. Follow-up testing will be necessary to determine the effectiveness of the treatment.

Dogs with severe heartworm disease may not tolerate the treatment to kill the adult heartworms. In this case, it may be safer to treat the resulting failure of their internal organs than to try to kill the heartworms. These dogs likely will not survive more that a few months.

Cats

The veterinary community only recently discovered that heartworm infection is more prevalent in cats than previously thought, and no heartworm treatment medications have yet been approved for use in cats. Once heartworm infection is diagnosed, three options are available.

The first option is to allow your cat’s body to handle the infection without specific treatment. This option may be the best for those cats that test positive for heartworms but have no apparent signs of heartworm disease. If the cat develops signs of heartworm disease, he will need to be re-evaluated.

The second option, which is for cats that show physical signs of heartworm infection, is to treat the signs of the heartworm disease and hope the cat outlives the heartworms, which can stay alive in the cat’s body for about two years. If you and your veterinarian pursue this avenue, your cat may have to be treated with oxygen and medication to help him breath and may need to be given drugs to remove fluid from the lungs. Continuing medical treatment is usually needed.

The third option is to treat the cat with drugs approved only for use in dogs. These drugs are known to have side effects, including respiratory failure and death, in a small percentage of cats. Your veterinarian will discuss these options with you.

This client information sheet is based on material written by Ernest E. Ward Jr., DVM.

 © Copyright 2002 Lifelearn Inc. Used with permission under license. September 14, 2007

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