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Heartworm (Dirofilaria immitis) is a parasite that lives in the right ventricle of the heart and pulmonary blood vessels. As adults, they are the width of thin spaghetti, up to 14 inches long and can live up to seven years.

This parasite is transmitted by mosquitoes and is necessary for the heartworm development. When a mosquito feeds from an infected dog, they also collect the microfilaria or heartworm larvae found in the bloodstream. Once in the mosquito, the microfilaria or young worms go through new stages of development. During the last growth stage, the microfilaria is ready to burrow back into the dog or other animals bloodstream upon the mosquitoes next feeding. Once back into the host animal, a coyote or canine, they then mature into adult heartworms. Its at this stage where they begin to clog the blood flow in the heart and causing damage to the pulmonary arteries by becoming a thickly wound pack of worms all flowing within the same space.

Image showing canine heart with heartworms

Signs of Heartworm

Signs of heartworms in dogs come almost always too late for a dog to be treated which makes preventative measures are so important. Fainting and weight loss are serious signs a dog is overcome by heartworms.

Prevention and Treatment of Heartworm

The good news is that there are common preventatives which kill the larvae before they become adults. It is essential every puppy starts heartworm treatment early on, especially if your dog is spending his days in the backyard or going to family outings with you. A puppy should start treatment at 8 weeks of age. Keep in mind, dogs over 7 months that haven't yet started treatment must be tested for heartworms before starting a preventative treatment or they can be at an increased risk of reaction. Talk to your veterinarian to get more details on when to start treatment and of what form.

Medications

Available medications to treat heartworm

Some of the common treatments given for heartworm are HeartGard and Interceptor. HeartGard Plus® comes in a chewable tablet which prevents Heartworm as well as treats for roundworm and hookworm. Interceptor prevents Heartworm while also treating roundworm, hookworm and whipworm.

Be sure to talk with your veterinarian so they can design the best solution to eliminate of the parasite is all its stages of live, larvae, microfilaria and adult.