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Preventing Heartworm In Cats

Although dogs are more likely to get heartworm, cats can become infested too. The worms are introduced into a host via a bite from a mosquito which is carrying the heartworm larvae. The larvae settles in the blood vessels around and often within the heart and lungs of the host, hence the name, where they could take up to eight months to become a full grown worm; adult heartworms can be in excess of six inches long. The worms will then breed and circulate more larvae around the bloodstream of the host for another mosquito to pick up. Heartworm is an infestation that is simpler to prevent than cure. The immune system of cats works harder than dogs to resist heartworms, sometimes successfully, although dead worms within the cat can cause problems too. According to the American Heartworm Society (AHS) there is no approved treatment for heartworms in cats but says that supportive treatments can be effective; heartworms can be fatal.

Heartworm symptoms

Your cat is at risk from getting heartworms in all 50 states of the U.S. However, heartworm is much more prevalent around the Atlantic and Gulf coast states. Your cat may exhibit symptoms that could easily be attributed to other conditions when it is really Heartworm Associated Respiratory Disease (HARD). Watch for breathing problems, vomiting, gagging, unusual lethargy, weight loss and even sudden death; heartworm infestation is often mistaken for allergic bronchitis or feline asthma. If you live in an area where there are mosquitoes then you should be concerned about possible heartworm infestation.


If it is at all possible, prevent mosquitoes from biting your cat. If your cat is an inside animal then this could be achieved by using animal safe home insecticide products. However, it could only take one mosquito bite and your diligence could be all for nothing. Therefore, talk to your vet about a heartworm prevention program for your cat. If your cat is older than seven months old it is likely that your vet will recommend testing your cat for heartworms before embarking on a preventative program; the AHS recommends heartworm testing. There are a number of products that your vet may recommend from chewables once a month treatments to monthly skin applications that can also control other parasites. Typically these medications may contain ivermectin, milbemycin oxime, or moxidectin. Take advice from your vet as to which method and product may work best for your cat and remember to give your cat the medication as per the instructions; timely treatment, especially during the mosquito season is vital. Also, although there are similar heartworm medications for dogs, often with the same drugs, the doses are very different, never give a cat dog medication or vice versa. The lifespan of a heartworm in a cat can be two to three years. Sometimes, if your cat has tested positive for heartworms but is not displaying any symptoms your vet may suggest preventative treatment for new larvae, six monthly scans of your cat, and simply to wait out the worm’s lifespan rather than resorting to surgery.

Read preventing heartworm in dogs.

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