Although most pet owners are well aware of the risks of heartworm disease in their dogs, it is less commonly understood how the disease affects cats. And while our dogs are routinely tested annually and are on monthly preventatives, many people do not realize that preventatives are also available for cats.
This handout should help you, as a cat owner, understand feline heartworm disease so you can make the most informed decision regarding heartworm testing and prevention for your feline friends.
Which cats are affected? Heartworm disease in cats has the same geographical distribution as in dogs, but cats are less frequently infected. Male cats are more often infected than females and generally have more worms. Because heartworm disease is transmitted by mosquitoes, cats who go outdoors are at a higher risk for exposure. Indoor cats are also at risk, however: one study showed that 30% of infected cats were strictly indoors. All ages have been shown to have the disease.
How do cats get Heartworm Disease? The disease is spread through the bite of an infected mosquito, which injects microscopic larvae into the cat’s bloodstream. These larvae grow and change over a period of months and then, as adult worms, reside in the heart and pulmonary (lung) arteries. And although cats are less easily infected than dogs, it can take only one worm to cause serious problems. In fact, most cats with heartworm disease are infected with six or fewer worms.
How would I know if my cat has the disease? Unfortunately, the symptoms of heartworm disease in cats are often non-specific. Some cats suffer from chronic vomiting. Others may have respiratory problems, especially coughing, which is often mistaken for asthma. Some cats may become seriously ill, very suddenly showing symptoms such as respiratory distress, collapse, seizing, and/or spitting up blood. In some instances, the cat dies without any warning.
How is it diagnosed? No one test is 100 percent accurate for feline heartworm disease, so we do not routinely test,cats every year like we do dogs. If heartworm infection is suspected, we rely on results from two tests (an antigen test, which checks for the presence of proteins from the heartworm itself, and an antibody test, which checks for the cat’s immune system response to heartworms) to help us make the diagnosis. Even these two tests combined are not a perfect screen for heartworm disease. Sometimes the suspicion of heartworm disease needs to be confirmed, or the degree of the disease assessed, with such tools as radiographs or ultrasound.
How is it treated? Unfortunately, the known treatments for feline heartworm disease carry high risks and are not recommended. What we do is support the cat with symptomatic care (for example, by using steroids to help with the secondary effects on the lungs) while the cat’s own immune system works to clear the body of the worms. Fortunately, heartworms in cats have a much shorter lifespan (only 2-3 years) than in dogs.
Can my cat be protected? Yes! Both oral and topical feline heartworm preventives are available by prescription from your veterinarian. We recommend all indoor/outdoor cats, and cats that travel to wooded areas or warm winter vacation spots, be protected with medication. Your cat does NOT need to be blood tested first. However, the dosage for cats is very different from the dog dosage, so don’t use your dog’s medication on your cat!
Please discuss with your doctor whether your cat needs to be on heartworm preventative.
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