Heartworms in Dogs and Cats: There’s No Such Thing As an Outdoor Only Mosquito

Heartworm is a common cause of heart and lung disease in both cats and dogs. Heartworms are transmitted by mosquitoes injecting microscopic larvae through the skin. Once the heartworms have matured they can mate and the females can release offspring called microfilaria. When they have matured they make their way to the heart (although other organs can also be infected with heartworms). The adult heartworms are about nine to eleven inches long and live in dogs for around 5-7 years and in cats for around 2-3 years.The cycle begins again when a mosquito takes a blood meal from the newly infected cat or dog and draws the microfilaria into its system.

Although heartworms are more common in dogs and outdoor cats, indoor cats can also be infected. As many as 25% of heartworm positive cats lived indoors exclusively. Only one or two heartworms in a cat are enough to cause sudden death and it only takes one infected mosquito to transmit the disease. A single dead worm can be fatal in cats as it can break away and cause a blockage of the pulmonary artery.

Heartworm disease in cats is different than in dogs, can be very difficult to diagnose and may mimic many other feline diseases. Cats usually test negative on the routine blood test done in the hospital, the worms are smaller and usually do not produce the microfilaria that circulate in the bloodstream.

There are no specific clinical signs for diagnosing feline heartworm disease. Cats that seem to be doing well may die suddenly. Cats usually have asthma signs, cough or even vomit. But with time, cats (and dogs) may show more severe symptoms such as congestive heart failure, weight loss, fluid build-up in the abdomen, weight loss, fainting spells, anemia, collapse or sudden death.

There is a treatment for adult heartworms in dogs, but it is very expensive and potentially harmful to the dog. Even if a dog has been given preventatives, it is still important to have annual checkups for heartworms by doing a blood test. If a dog has heartworms and it is given a dose of preventative, there can be a reaction that is detrimental to the dog, even deadly.

Unfortunately, unlike dogs, there is not a treatment for adult heartworms in cats. This is why it is much better to just prevent them in the first place. Luckily there are several excellent medications which can prevent heartworm if given as directed.

*See heartworms in action on video!

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