#VirbacVetTalk Heartworm Q&A

Q: What should a pet owner know about heartworm disease in cats and dogs?
A: Heartworm disease is a serious and potentially life-threatening disease transmitted by mosquitoes to both outdoor and indoor pets. Heartworm disease is diagnosed around the world. For more information regarding heartworm disease in dogs and cats, please visit: heartwormsociety.org and capcvet.org.

Q: What other animals get heartworms?
A: Many animals are capable of becoming infected with and harboring heartworms. Canines and wild canids, felines and wild felids, ferrets, raccoons, and other mammals such as sea lions are also capable of being infected by these internal parasites. Although it is rare, humans may become infected with heartworms.

Q: Why are they called "heartworms?"
A: Heartworms get their name because they live in the heart and the associated blood vessel between the heart and lungs.

Q: How does my pet get heartworms?
A: Heartworm disease is transmitted by the bite of a mosquito. A mosquito will take a blood meal ingesting microfilaria (microscopic baby worms) from an infected animal. The microfilaria will go through two molts in the mosquito becoming an infective stage 3 larvae. This process takes approximately 2 weeks. The mosquito will deposit the infective larvae around the next animal's bite wound, where they will enter the animal. The larvae will molt into stage 4 larvae once inside the body, and over the next 6 months, will migrate and mature into adult heartworms in the heart and pulmonary artery of the animal. The mature heartworms will produce microfilaria that enter the animal's bloodstream waiting to be ingested through a blood meal by another mosquito. The mature heartworms can live 5 to 7 years in canines and 2 to 3 years in felines causing damage to the heart, lungs, and potentially other organs.

Q: What are the signs of heartworm disease?
A: Signs of heartworm disease in dogs include coughing, exercise intolerance, respiratory difficulties, weight loss, and in severe cases, organ failure and fainting. Because heartworm disease is a progressive disease, early signs may go undetected. Yearly testing in the dog and cat are encouraged for this reason. Earlier detection means better chance of recovery for the pet.

Q: Do cats show the same signs of heartworms as dogs?
A: Cats tend to exhibit more respiratory type signs than dogs such as coughing and/or asthma-like episodes. Also, cats may experience vomiting, lack of appetite, or neurologic signs. Unfortunately, sudden collapse or death due to heartworm infection may be the only sign in a cat.

Q: Is heartworm disease the same in cats as in dogs?
A: Heartworm disease is different in cats than in dogs. In cats, most worms do not survive to adulthood and if they do, there are fewer numbers, such as 1 to 3 parasites, found in the heart. Many cats with heartworms only harbor the immature stage. Therefore, there is no treatment for heartworm disease in cats making prevention key to protecting cats.

Q: Is heartworm disease only a problem in the south?
A: No; heartworm disease has been identified in all 50 states, which is why the use of heartworm prevention is important regardless of where one may live. Traveling with pets may put them at increased risk of exposure of heartworm disease, especially if visiting an area where increased mosquito populations exist such as the southern United States.

Q: What should I know about testing my pet for heartworms?
A: Annual heartworm testing is recommended for both indoor and outdoor pets, whether currently receiving prevention or not. Dogs should have an antigen heartworm blood test performed, and cats should have both antigen and antibody heartworm blood tests performed. If a pet has missed a dose(s) or their heartworm history is unknown, the pet should have an initial heartworm test performed with a follow-up heartworm test performed 6 months later. Antigen tests detect female adult heartworms only. On rare occasions, an echogram may be recommended for further detection of heartworms residing in the heart.

Q: How does heartworm prevention work?
A: All heartworm preventions work by eliminating the immature larval stages (L3 and L4) of the heartworm parasite. It is crucial that heartworm preventatives be administered every 30 days if giving oral or applying topical, or every 6 months if injectable, to prevent the heartworm from developing into an adult. Heartworm prevention is recommended for all pets to prevent heartworm disease. There is currently a heartworm treatment labeled for use only in dogs. See the American Heartworm Society’s Heartworm Guidelines here.

Always consult with your veterinarian if you have additional heartworm questions or if you feel that your pet might be exhibiting signs of heartworm disease.

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