An estimated 1 million U.S. dogs are infected with heartworms, and that number continues to rise as heartworm disease becomes more widespread. Effective preventives can save these pets from painful, expensive heartworm treatment—or worse, death—but many pet owners underestimate disease prevalence and dismiss the importance of consistent prevention. In honor of Heartworm Awareness Month, and to clear up the heartworm confusion, the Animal Hospital of Parkland team is providing answers to heartworm FAQs.
Question: How are heartworms different from other worms?
Answer: Most worms you’ve heard about, including roundworms and hookworms, live in your pet’s intestines after being picked up from contaminated environments. Mosquitoes transmit heartworms, which can live inside the heart and large blood vessels. This preferred location allows heartworms to significantly damage organs and lead to eventual death. Serious complications from intestinal worms are far less common, and they are easier to treat than heartworms.
Q: What happens to dogs who get heartworm?
A: A susceptible dog (i.e., a dog not taking a heartworm preventive) could become infected by a heartworm-carrying mosquito that bites them and then deposits heartworm larvae on their skin. The larvae travel through tissue or the blood until they reach the heart, where they mature into adults around six to seven months later. The adult worms can grow to a foot long, and they reproduce easily inside a canine host, making the host an infection source for other mosquitoes, and subsequently, other pets.
Heartworm infection usually does not show clinical signs at first, but a long-standing infection or high worm numbers can lead to heart damage and heartworm disease. Signs include:
- Exercise intolerance or fatigue
- Coughing
- Poor appetite
- Weight loss
- Heart failure
Q: Are cats susceptible to heartworm infection?
A: Cats are not a natural heartworm host, but they can still become infected. Heartworms do not survive or thrive as well in cats as in dogs, which means infected cats usually carry only a few worms. Unfortunately, this smaller worm burden doesn’t translate to fewer negative effects. Infection in cats usually leads to asthma-like respiratory problems, but can also result in chronic vomiting, weight loss, poor appetite, seizures, heart issues, or sudden death.
Q: How is heartworm diagnosed?
A: Sick pets with suspected heartworm disease can be tested using a combination of blood tests and imaging to detect and locate the heartworms. For dogs, routine heartworm blood testing helps us detect and treat infections before clinical signs, which helps avoid more serious complications associated with long-standing disease. Routine screening is not as accurate for cats and is generally not recommended unless a cat shows heartworm infection signs. All pets should be heartworm tested prior to starting a prevention regimen.
Q: How do heartworm preventives work?
A: A heartworm preventive is a monthly medication applied topically or given orally, which prevents development of heartworm infections. Preventives work retroactively (i.e., they kill larvae that were transmitted in the month prior to each dose). Infected mosquitoes may continue to bite your pet after their dose, so you must continue the medication on an ongoing basis for the best protection.
Q: Can I skip heartworm prevention during the winter months?
A: Because of how heartworm prevention works, skipping months is not recommended. Mosquito activity and weather patterns are difficult to predict, and only one bite on one warm day can lead to a deadly infection. Year-round prevention is best for all pets, including indoor cats, because mosquitoes can be sneaky. Studies show up to one-quarter of heartworm-infected cats live exclusively indoors.
Q: Is heartworm prevention worthwhile?
A: Financially speaking, heartworm prevention is a far better choice than heartworm treatment. Prevention for a medium-size dog for a year costs around $100 to $150, but treatment can cost 10 times more. Costs aside, the better option is prevention, which helps avoid long-term heart damage or other health consequences, and spares your pet the painful injections and long-term cage rest required during treatment. Prevention is the only option for cats, because safe treatments are not available.
Heartworms cause a deadly but easily preventable disease in pets, and all pets are susceptible. Animal Hospital of Parkland carries multiple heartworm prevention options, and we can discuss which product is best for your individual pet. Contact us to learn more about heartworm disease, to schedule your pet’s next wellness visit, or to schedule a routine heartworm test and begin a prevention regimen.
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