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Symptoms Of Heartworms In Dogs

Updated on July 1, 2012

Heartworms in dogs introduction

The heartworm is a small parasitic roundworm that looks like a string of translucent thread. Despite its reference to the heart, the worm usually settles in the lung arteries, leading to fatal lung tissue and vessel damage, extensive damage may also lead to organ damage.

Dogs are what is known as the "definitive" host, meaning they are the vessel through which these worms reach adulthood. But canines, while the most common host, are not alone in their plight with the parasite. Other pets such as cats and ferrets (and occasionally even humans) are sometimes forced to contend with heartworms.

Transmission is usually difficult to predict and control because the larvae are deposited under the skin by infected mosquitoes. The larvae then travel through the veins to their chosen nestling ground where, around four months later, the reach maturity and begin their potentially fatal course.


Buying medicine online for a case of canine heartworms is not recommended. However, if you do, please read the pet owner instructions in the link provided above.

Symptoms of heartworms

Initially there are no symptoms of heartworms in dogs, making it difficult to spot the illness early. As the disease reaches an advanced stage however, complications begin to arise and may begin to multiply as time goes by.

  • Coughing
  • Lethargy
  • Labored breathing
  • Fainting spells
  • Rasping sounds coming from the lungs
  • Congestive heart failure
  • Fluid retention (chest area)
  • Tachycardia (rapid pulse)
  • An enlarged liver
  • Dry coat
  • Rapid weight loss
  • Vomiting and diarrhea
  • Death

A vet can diagnose heartworms by using one of several different methods including the modified Knott test or an antigen test. Dogs should be routinely screened for heartworms, especially between the ages of four and eight.

Heartworm treatment in dogs

Heartworm prevention is relatively cheap, however, treatment presents some risks and is very expensive.


Preventing heartworms is a relatively simple process, but your veterinarian may recommend different solutions based on where you live and how much time your dog spends outdoors. Bear in mind that heartworms have been diagnosed in all 50 states. There are three main types of prescription prevention solutions:

  • A topical liquid 
  • Via injection 
  • Via tablet or pill 
Heartworm treatments can also be combined with other useful treatments such as flea prevention. 


Different stages of the disease require different treatments, potentially leading to anything from a series of injections to surgery (in critical cases).

Immiticide injections are commonly used to treat heartworms in dogs, but because of its chemical toxicity (it is an arsenic compound) it presents some risks.

Once the injections and treatment has been administered, the death of the heartworms can clog up arteries, thus requiring the pet owner to make sure that the dog limit exercise for six weeks after treatment. Exercise can lead to death!

Also, remember that heartworms in a non-infectious disease, and your other pets (and yourself) do not run the risk of being infected.

Thank you!

Thank you for taking the time to read this article, for any questions or concerns, feel free to use the comments module below this text.




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    • profile image


      6 years ago

      How expensive is heartworm treatment?

    • profile image


      6 years ago

      Heartworms are very scary but good information for us to know and know this awful symptoms.

    • profile image


      6 years ago

      wonderful information. thank you.

    • profile image


      7 years ago

      I adopted my dog and the papers we got for her says that she was treated for heart worms, but she is showing signs that she has them. Took her to the vet and the vet says she is ok. The vet told me that she has allergies. I feel like I should get a second option. It is hard to see a family member sick and can't do anything about it.

    • profile image


      7 years ago

      my yorkie pup is about 10 months old....she has had a dry cough since she was just few months old and I took her to the vet who insisted she has allergies but her coughing seems to be more intense when she is active and she has gotten to where she is vomiting often. She is active and hyper and still has an appetitie but I am scared she may have a more serious problem such as heartworms or some other disease than allergies. If either of these is a possibility what else do I need to look for to be more secure in my worries or am I just being an over protective mother?

    • OnTheRock profile image


      7 years ago from Tortola, British Virgin Islands

      My dog has a very dry coat- hope it isn't heartworm! He does get Revolution each month.

    • william.fischer29 profile image


      7 years ago

      Great information and useful. Thanks.

    • L A Dreamin profile image

      L A Dreamin 

      7 years ago from Pennsylvania

      Great information, had to vote useful :) thanks!

    • Diana Lee profile image

      Diana L Pierce 

      7 years ago from Potter County, Pa.

      A good thing to know, thanks.

    • sonia05 profile image


      7 years ago from india

      very useful and informative hub!!

    • GetSmart profile image


      7 years ago

      This is such good information to know. Thank you.

    • RhondaCzech profile image


      8 years ago from Ontario, Canada

      Good to know! I live in an area where we get lots of mosquitoes. I have a 19 month old pitbull/boxer mix and just recently adopted her, I don't know her history, I will take her in now to have her checked.

      Thankyou for your informative hub.

    • profile image


      8 years ago

      Get the yearly heartworm injection and save yourself the hassle and worry. It's perfectly safe.

    • thooghun profile imageAUTHOR

      James D. Preston 

      8 years ago from Rome, Italy

      Thanks again Marisue and Faerie!

    • Faeriephenomenon profile image


      8 years ago from USA

      This is a great article with very useful info. Thanks for the advice and treatments. :)

    • profile image

      interceptor for dogs 

      8 years ago

      thank you very much for the article. it may save the life of many pupies.

    • marisuewrites profile image


      8 years ago from USA

      Great information for us pet lovers!

    • thooghun profile imageAUTHOR

      James D. Preston 

      8 years ago from Rome, Italy

      Thanks for you comments everyone!

    • MPG Narratives profile image

      Marie Giunta 

      8 years ago from Sydney, Australia

      We give our dog heartworm tablets every month along with her flea treatment. She is now 4 and as you mentioned they may be a risk between 4-8 years I will keep a more close eye on her for the symptoms you wrote. Thanks for the info, very useful.

    • ZarkoZivkovic profile image


      8 years ago from Serbia

      We had a problem with roundworms with our dog, luckily for us and the dog it's much easier to get rid of roundworms than heartworms! Nice info.

    • MKayo profile image


      8 years ago from Texas

      Very informative, but I just had to look away from the dog heart in a jar. I wish more folks would take better care of their animals.


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