Symptoms of Heartworms in Cats


Heartworm disease is a well-known source of affliction among dogs, but heartworm also affects felines. Unlike infected dogs, there's no actual treatment for the disease in cats. The best you can do is have the vet test Kitty for the presence of heartworm microfilaria, or baby heartworms. If tests are negative, your vet can prescribe a heartworm preventive, a monthly topical or oral suspension, that will keep the cat from acquiring heartworms.

Feline Heartworm Disease

  • Cats pick up heartworm after an infected mosquito bites them, transferring heartworm larvae into the bloodstream. It take about eight months after that bite for larvae to develop into full-grown heartworms inside the cat's body. At first, the larvae dwell in a host's subcutaneous tissues, but they eventually migrate to the muscles. From there, they head to the heart, lungs and associated arteries. Unlike dogs, who might have dozens of heartworms infesting them, cats generally have just a few. Those few are sufficient to cause death.

Heartworm Symptoms

  • An acute heartworm attack can kill your cat suddenly, with no prior symptoms. This occurs if heartworms migrate into the lungs or the cat's pulmonary arteries, blocking blood flow. According to the U.S. Food and Drug Administration, as adult heartworms die, toxins are released into the bloodstream, causing lung damage and either breathing problems or sudden death. One worm's death is sufficient to cause feline fatality. Other signs of an acute attack include collapse, convulsions, vomiting, diarrhea, sudden blindness, rapid heartbeat and breathing difficulties.

    A cat chronically ill with heartworms -- as opposed to an animal experiencing an acute attack -- tends to cough and to suffer appetite loss and subsequent weight loss. Chronically ill cats also exhibit breathing problems, perhaps resulting from fluid in the chest cavity. Your vet might initially mistake these symptoms for feline asthma, so thorough testing is necessary.

Heartworm Testing

  • It's more difficult to diagnose heartworm disease in a cat than a dog. Only a small percentage -- less than one-fifth -- of cats harboring grown heartworms have microfilariae circulating in the bloodstream. While a positive microfilariae test indicates the presence of heartworms, a negative test doesn't rule them out. Antibody testing isn't particularly effective, as up to 25 percent of infected cats will still have negative antibodies, and up to 90 percent of cats with positive antibodies don't have heartworms. The most effective way to determine whether or not a cat has heartworms is via a chest X-ray or an ultrasound.

Heartworm Treatment

  • If your cat is diagnosed with a heartworm infection, the best your vet can offer is a prescription for corticosteroids to ease coughing and inflammation. She'll advise you to keep Kitty as quiet as possible, restricting his activity. Once infected, heartworms dwell in felines for approximately two years before dying. According to the Merck Veterinary Manual, cats are more likely to die from heartworm disease than dogs, but between 25 percent and 50 percent of felines survive heartworm infection.

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