Heartworms in Dogs, Cats, and Ferrets


Ask just about any dog owner and they will tell you they have their four legged friend on heartworm prevention every month. But what about their frisky feline or their frolicking ferret? And what really is a heartworm, and how are they spread? We are very lucky now in veterinary medicine to have so many drugs on the market to protect all of our best friends-or at least those that walk on all fours.     

So what exactly is a heartworm? Heartworms are parasites found in the heart and the main blood vessels of the lungs of infected dogs and ferrets.  They can and do live in the hearts of cats as well; however, the cat’s heart is not favored by the worms. This means that the heartworms will find another place to live inside the cat, including the brain.   Infected dogs, cats, and ferrets may die unless heartworm infection is diagnosed and specifically treated, however the infection can be easily prevented.

How are heartworms spread and is my pet at risk?  The heartworm life cycle starts with an infected pet.  The mosquito bites the animal and picks up baby heartworms (Life Stage 1, or L1).  The baby heartworms mature in the mosquito (through L2 to L3) and the mosquito injects the L3 stage into our pets.  The L3 matures in the skin and tissues (through L4) on the way to the heart and lungs where they finish maturing (through young adult to adult).  The adults mate and produce more L1’s for the next mosquito to pick up when it bites. If a mosquito that has bitten a positive dog then bites your pet, your little critter will likely be infected with heartworms.  All pets that are not on preventative medicine are at risk, since the disease can be spread by one infected mosquito. 

How would I know if my pet were infected? If a pet is positive for heartworms a few clinical signs may or may not be apparent. Symptoms can include weight loss, trouble breathing, or evidence of heart problems. However, these signs can also be indicative of other health issues. A heartworm test can be run on a dog simply by taking a few drops of blood and using a quick in hospital test. Cats are a bit trickier, however. We are able to test for exposure to the worms in cats, but it is very difficult to detect the presence of the worms themselves. A more conclusive diagnosis relies on analyzing the cat’s symptoms. Many cats will have difficulty breathing or asthma-like symptoms, and chest x-rays can be taken as well to help evaluate cardiac conditions. 

Can my pet be treated?  Luckily, dogs can be treated if a blood test shows they are positive for heartworms, although the treatment can be long and uncomfortable. Cats unfortunately are not so lucky. To date, there is no approved treatment for heartworm positive cats, thus their lifespan is greatly shortened if they become infected. 

What needs to be done in order to prevent this from happening to my pet? The answer is quite simple-monthly prevention. There are quite a few options on the market and the dosing is very easy-either a monthly chewable pill or a topical treatment. Two of the best products and most often recommended are Trifexis, a tablet given with food for dogs, and Revolution, a topical dose for cats and ferrets. Both excellent ways of preventing heartworms, they also serve as flea prevention and even keep away those internal parasites that are, unfortunately, too often found as well. 
One of the best things you can do for your pet is to protect them from heartworms and, as we say, “an ounce of prevention is worth a pound of cure”. Keeping your pet healthy and safe will undoubtedly ensure a lifetime of rewards-for you and for all of your shedding, chewing, eating, wild, purring, barking, and overall happy loved ones. 

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Austin Vet Care at Metric


12419 Metric Blvd Austin, TX 78758

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Sat: 8am-12pm, Sun: Closed