Our veterinarians prescribe preventive medication and provide wellness recommendations because they want the absolute best for your pet, just like you do. However, there’s not enough time during your pet’s annual checkup for us to pass along all the information we would like. So, we present the following facts about heartworm disease to dispel some common misconceptions.

Myth #1: Heartworm is no big deal.

Heartworm infection is typically fatal if not treated. Untreated dogs can harbor as many as 250 worms, and each worm can grow to 12 inches long. This worm load puts a large strain on the heart and ultimately leads to heart failure. Although cats are not the natural host for heartworms and the worms cannot reproduce inside them, even a single worm can wreak havoc on their health and cause sudden death.

Myth #2: Heartworm affects only dogs.

Heartworm can infect domestic animals, such as dogs, cats, and ferrets, as well as wild animals, such as wolves, foxes, and coyotes. Ferrets are exceptionally sensitive to heartworms because they are small, and, like cats, just a single worm can significantly impact their health.

Myth #3: Infected animals can transmit the disease to another animal.

Only infected mosquitoes transmit heartworms when they bite an animal and deposit the heartworm larvae, called microfilaria. The mosquito must be infected for some time because the heartworm parasite must go through an incubation period inside the mosquito before it can be spread.

Myth #4: I don’t need preventive medicine because I can treat my pet if she shows signs of disease.

Many heartworm-positive dogs show only mild signs, including coughing, struggling to exercise, fatigue, loss of appetite, or weight loss. Some animals don’t exhibit any signs before their sudden death. There is no safe treatment available for cats infected with heartworm disease, and treatment for dogs is more difficult and costly than preventing the disease in the first place. Since heartworm is almost completely preventable, it’s not worth waiting until you see signs of the disease.  

Myth #5: Heartworm preventives aren’t safe, effective, or affordable.

A year’s supply of heartworm preventive medicine will likely cost $35 to $225, depending on the size of your pet—less than a weekly coffee at Starbucks. Many studies have proven that heartworm medications are safe for your pet for her lifetime. Heartworm preventive given on time at the appropriate dose is nearly 100% effective.

Myth #6: Pets don’t need year-round preventive, or prevention is not required in some geographic areas.

Thanks to irrigation, mosquitoes (and heartworm disease) are found everywhere in the United States, including desert areas once considered “safe.” If you have mosquitoes and animals, you have a risk of heartworms. And, while the risk of heartworm disease decreases in winter, some mosquitoes can live indoors or survive the colder temperatures, so pets should be given preventive year-round in every state.

Myth #7: If my pet gets preventive medication, I don’t need to test her for heartworm.

The American Heartworm Society recommends an annual heartworm screening for all pets over 7 months of age. Infection can set in if just one medication dose is missed. Always have your pet tested after a missed or delayed dose, and follow up with a second test in 6 months when any larvae will have matured. Even pets on preventive year-round should be tested annually.

Myth #8: A negative heartworm test means my pet does not have heartworms.

The most commonly used test looks for adult female worms, so false-negative results are possible if the pet has only a few worms, immature female worms, or only male worms. False-negative results are another reason annual testing, or testing six months after a missed dose, is important.

Myth #9: Heartworm disease is always fatal.

The disease is treatable for dogs, but treatment is intensive and expensive. Treatment usually includes a course of antibiotics and monthly medication injections to kill adult heartworms. Treatment also includes strict exercise restriction while the body clears dead worms to help avoid a potentially deadly heart blockage. An animal with a large worm burden may require surgery. Outcomes vary depending on the duration of infection, immune response, the animal’s age and general health, and the number of worms present. Cats diagnosed with heartworm disease may require supportive care to mitigate symptoms of the disease, but treatment to kill the worms in cats is not available.

Myth #10: I shouldn’t adopt a dog who is heartworm-positive.

Even though a dog can be treated successfully, you shouldn’t take on the responsibility of a heartworm-positive animal unless you have the time necessary, can maintain the strict directions, and have the financial resources to complete treatment.

Our veterinary team can answer any questions you may have about heartworm disease. Contact us to schedule your pet’s annual preventive appointment and checkup.