cat with bandana
While more common in dogs, cats also suffer from deadly heartworm infestation. Heartworms, spaghetti-like white creatures, can measure 1-foot long and cause an inflammatory response in your pet’s heart and lungs. Heartworms are especially prevalent in hot, humid parts of the country, especially in the South.


As with many infectious diseases, mosquitoes are involved. When a mosquito bites an infected animal, especially a fox, wolf, dog or coyote, it ingests microscopic baby heartworms. The mosquito then passes these microfilaria to its next victim. About six months later, these larvae mature into adults. Heartworms can live in a dog for up to seven years and in a cat for two or three years. Additional larvae can enter your pet during each mosquito season, upping the concentration of heartworms. They migrate toward the lungs and right ventricle of the heart. Dogs make better heartworm hosts than cats, so the worms invading cats sometimes die before reaching maturity.


The most common symptoms of heartworm infection in cats include:

  • Diarrhea
  • Rapid, labored breathing
  • Vomiting
  • Weight loss
  • Lethargy


Again, heartworm infestation is not very common in cats, but once your veterinarian suspects the problem, he or she might order blood tests, chest X-rays, ultrasound imaging and a test to check whether the cat’s blood contains certain antibodies to heartworms. Cats with heartworms typically have no more than six heartworms—compared to around 30 in dogs—but even one can make your cat very ill.


In some lucky cats, heartworm infestation spontaneously disappears. This might be thanks to the cat developing a strong immune response that kills the heartworms.

Usually, the infection slowly progresses. Unfortunately, there is no safe treatment for heartworm in cats. The medicines used to cure dogs of heartworms are too strong to be used for cats.

If your cat is diagnosed with heartworm infestation but is not showing severe signs, your vet will probably want to monitor the condition with regular chest X-rays. If the blood vessels associated with the lungs are affected, your cat could develop heartworm-associated respiratory disease. Your vet might treat this with small doses of prednisone. Other supportive therapies for heartworm disease include oxygen therapy, intravenous fluids, antibiotics and cardiovascular drugs.

Heartworms can migrate to other parts of the cat’s body, including the eye, spinal cord or brain. Blood clots may form when adult heartworms die.


If you live in an area where mosquitoes and heartworms are prevalent, it is important to put your pets on a monthly regimen of preventative drugs. Since mosquitoes all too easily get inside houses, indoor cats are also at risk. Talk to your vet about which preventative drug is best for your cat.

Worried about heartworms? Call our office today and we can discuss testing, treatment and preventative measures against this insidious parasite.

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