heart·​worm ˈhärt-ˌwərm How to pronounce heartworm (audio)
: a filarial worm (Dirofilaria immitis) that is a parasite especially in the right heart of dogs and is transmitted by mosquitoes
also : infestation or disease caused by the heartworm

Examples of heartworm in a Sentence

Recent Examples on the Web Any dog infected with heartworm will also be prescribed a heartworm preventive. Claire Rafford, The Indianapolis Star, 21 June 2022 Meanwhile, there is another mammal known to become infected with heartworms: humans. Stephen C. George, Discover Magazine, 24 July 2023 Even medication to treat heartworm disease can be toxic or cause other side effects. Stephen C. George, Discover Magazine, 24 July 2023 But their ability to carry and transmit assorted diseases like West Nile Virus, Zika (not to mention malaria and dengue in other parts of the world) and even heartworms in dogs, while rare in occurrence, makes some people put mosquito control high on their to-do list. Paul Cappiello, The Courier-Journal, 14 July 2023 An animal can contract heartworm when it's bitten by a mosquito that has heartworm larvae. Claire Rafford, The Indianapolis Star, 21 June 2022 This means protecting them from pests and health threats that can range from heartworms to fleas and ticks. Amber Smith, Discover Magazine, 24 June 2023 Lemonade also offers the Preventative and Wellness Package, which covers up to $295 per year for items such as a heartworm test, bloodwork, and three vaccines. Better Homes & Gardens, 12 Aug. 2021 Savageau also recommends keeping up with heartworm prevention by giving your pup a deworming pill as instructed by your vet. USA TODAY, 15 June 2023 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'heartworm.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

First Known Use

1877, in the meaning defined above

Time Traveler
The first known use of heartworm was in 1877

Dictionary Entries Near heartworm

Cite this Entry

“Heartworm.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/heartworm. Accessed 6 Dec. 2023.

Medical Definition


heart·​worm -ˌwərm How to pronounce heartworm (audio)
: a filarial worm of the genus Dirofilaria (D. immitis) that is especially common in warm regions, lives as an adult in the right heart especially of dogs, and discharges active larvae into the circulating blood whence they may be picked up by mosquitoes and transmitted to other hosts and that may infect humans causing local pulmonary infarction but does not achieve sexual maturity in the human organism
: infestation with or disease especially of dogs caused by the heartworm, resulting typically in gasping, coughing, and nervous disorder, and when severe commonly leading to death

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