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Heartworm Information and Prevention

By: Dr. Amanda Landis-Hanna
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Heartworm disease is one I have fought for a long time.  Growing up in the southeast, heartworm disease was always recognized to be year round, because we never got snow.  As I continued to practice, moving further north, I noticed many pet parents did not give heartworm prevention year round.  The American Heartworm Society ( recommends year round prevention, as heartworm disease has been found in all states, except Alaska.

Heartworms may seem like an odd topic in the fall, because in many areas mosquitos are not as active.  As a practicing vet, however, I diagnosed cases of heartworm disease during all the seasons.  Most dogs receive an annual blood test to check for heartworms, which may be the first sign of a problem, even if the disease has been present for several months.  All too often, the pet was “taking” heartworm prevention intermittently, and the pet parent would ask, “What happened?  What went wrong?”  It is a heartbreaking conversation to have, because often the problem was a simple mistake, or an error in belief: Yes, heartworms are a year round disease.

If you are less familiar with heartworms, here is a short overview:  Heartworms are a parasite of the heart and lungs.  They are passed by an infected mosquito bite.  The larval heartworms move through the body and grow, later making baby heartworms.  Heartworms are preventable.  Heartworm prevention is available in oral, topical, and injectable forms, with generic and brand name options available. 

Many people believe that heartworms are a seasonal disease, only existing in the summer when mosquitos are at their worst.  In some areas of the world, that is the case.  But in the United States, heartworms have been discovered year round.  Treatment for mosquitos in the environment can help reduce the risk for heartworm disease, but prevention is the only way to protect consistently.

Heartworm prevention acts to kill the larval parasite (Dirofilaria immitus) before it grows to maturity.  Because it kills the larva, it needs to be given while the parasite is still young.  Many topical and oral heartworm preventions are given once a month, to ensure efficacy to kill the larval worms.  If a mosquito bites your dog in November (which definitely happens here in Virginia!), but the last dose of heartworm prevention was given in September, your dog is still at risk for heartworm disease.

What makes heartworm disease so problematic is that it is often insidious.  When a pet has a few worms, she may not show many symptoms externally, even though she is incurring damage to her heart and lungs.  By the time she starts coughing or a decreased appetite (both symptoms of heart failure), permanent damage has been done.

Additionally, heartworm disease is problematic to treat.  Unlike intestinal parasites that require a simple deworming, heartworm disease is much more delicate as it involves the heart and lungs.  Patients often require multiple rounds of treatment, and may need to be hospitalized for several days or a week after treatment.  The medication to treat heartworm disease is often expensive, and may have side effects.  Dogs who are being treated for heartworm disease must rest extensively during the recovery period.  Too much activity immediately following treatment can lead to severe side effects such as a blood clot or death.  Voyce Pro can be utilized to monitor your pet after heartworm treatment, to ensure maximum rest and recovery.

So as we enter these cooler months, please remember to give your pet her heartworm prevention.  If you have difficulty remembering to give prevention, you can use the reminder system in Voyce to help keep it top of mind.  Because far better than treating heartworm disease, is preventing it year round.

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Posted on Nov 09, 2015 by VOYCE Health
Vets & Experts