Parasites have always plagued dogs and cats, and while most are easily treated, heartworms can lead to serious consequences. To best protect your pet, you need to know how to separate heartworm disease fact from fiction. Memorial Villages Animal Hospital is busting heartworm myths and sharing heartworm truths, so you are better informed and your pet is better protected.

Fact: Mosquitoes transmit heartworms to pets

Mosquitoes can pick up heartworm larvae from infected pets and transmit them to new hosts after 10 to 14 days. An infected dog, coyote, wolf, or fox living in your neighborhood greatly increases the chances of a heartworm-positive mosquito biting your pet. Once inside their new host, the heartworm larvae travel through the body until they reach their target organs, where they grow into foot-long adults.

Fact: Heartworms live in infected pets’ heart, lungs, and blood vessels

Adult heartworms reside in their host’s heart, lungs, and associated blood vessels. They cause inflammation and damage to these tissues, and can eventually lead to heartworm disease, heart failure, or death in severe or long-standing cases. Outward signs in infected pets are generally not obvious at first, but the following may eventually develop:

  • Coughing
  • Fatigue
  • Abnormal fluid accumulation in the chest or abdomen
  • Weight loss
  • Collapse or sudden death

Fact: Heartworm treatment is painful, expensive, and risky

Heartworms are difficult to kill once they reach adulthood, when the only effective treatment is a painful injection series that puts the pet at risk for toxic reactions to dying worms. Pets must be strictly cage-rested throughout treatment, and require antibiotics and steroids to reduce bad reactions and inflammation that could lead to a blood clot. The entire process can take several months and cost more than $1,500 per pet. 

Fact: Heartworm prevention is highly effective in protecting pets from infection

A white fluffy dog intently looks at a treat held by a person wearing a blue shirt, capturing a moment of anticipation and focus in a session of pet behavior guidance.

Heartworm prevention is the preferred method to keep pets safe, because heartworm infection and treatment involve several risks. Heartworm preventives contain low doses of safe dewormers, which are effective in killing heartworm larvae, but cannot kill adults. Heartworm larvae can only be killed during a narrow time window, so heartworm preventives must be administered monthly, year-round. A year’s worth of heartworm prevention medication typically costs less than $150, which is a significant savings over heartworm treatments.

Myth: Cats are immune to heartworm infections

Dogs are the preferred host for heartworms, but cats are still at risk for infection. Many cats mount an immune response that kills heartworm larvae before they reach adulthood, effectively preventing infection, but in some cats, the larvae do survive to adulthood. Only a few worms can cause cats significant respiratory disease, and sudden death may be the first and only heartworm disease sign in a small percentage. Because predicting which cats are susceptible to heartworm disease is not possible, and because cats cannot be safely treated with the same protocol as dogs, year-round prevention is vital for all cats.

Myth: Skipping a few months of heartworm prevention is OK

Skipping only one or two doses of heartworm prevention provides the window that heartworm larvae need to take hold, leaving pets vulnerable to infection. Especially in warmer climates when mosquito activity continues year-round, monthly doses are vital for complete protection. Heartworm preventives are also effective at controlling several intestinal parasites, which adds another benefit by keeping other pets and human children safer.

Myth: Natural mosquito repellants are enough to protect my pet

Mosquito control strategies, including natural, pet-safe repellants, will help reduce, but cannot completely eradicate, heartworm risk. Infection requires only one bite from one infected mosquito that can easily slip through the repellant’s defenses. Prescription heartworm prevention from your veterinarian is the only way to guarantee protection.

Myth: Heartworm prevention is toxic to pets

Some pet owners believe that because parasite preventives can kill parasites, they can also harm their pet’s bodies. These medications have been extensively tested and used for decades with a reliable safety track record. A few dog breeds, usually in the herding family, may possess a gene (MDR-1) that makes them more sensitive to certain drugs, including ivermectin—one of the main drugs used in heartworm preventives—but the doses used in heartworm preventives are so low that they should not adversely affect dogs who test positive for the gene.

Heartworms can threaten your pet’s health, but year-round prevention is a cost-effective, easy-to-administer method that can keep them safe. Contact the Memorial Villages Animal Hospital team to learn more about our heartworm prevention and testing protocols, or to schedule your pet’s next wellness examination and parasite consultation.