Heartworm Disease

Heartworm Disease in Dogs


Heartworms (Dirofilaria immitis) are parasites that infect dog (and rarely cats).  The worms live in the veins near the heart and cause direct damage to the heart and lungs.  They can also damage other organs in the body by reducing blood flow.

The heartworm is transmitted to pets through mosquito bites.  When a mosquito feeds on a dog with heartworm disease larva (immature heartworms) enter the mosquito from the dog.  These larva then grow inside the mosquito to a stage that is able to infect other dogs.  The mosquito then bites another dog and infects them with heartworm disease.  Dogs can become infected with heartworms through as little as one mosquito bite.  Wild dogs, such as coyotes, can also become infected with heartworm disease and act as reservoir since they cannot be treated.  This is important to know because having a heartworm positive animal locally greatly increases the chances that mosquitoes in that area will be carrying heartworm disease. Click here to watch a video about heartworm disease transmission

Hamilton is within the area that sees the highest incidence of heartworm disease within Canada (around the southern great lakes).  For this reason we take the risk of heartworm disease very seriously and recommend the pets be tested and take prevention medication during the mosquito season (usually June – November).  It is also important to keep in mind that pets travelling to warmer areas in the United States during the winter months may also need heartworm protection.  Please ask your veterinarian if you are planning to travel.

Treatment for heartworm disease in available but it is expensive, lengthy and can be risky to the patient.  It can take up to 3-4 months to treat and involves at least 2 months of cage rest.  The cost can easily escalate to over $1000 dollars.   Prevention is much easier and less costly.  Testing and prevention can cost as little as $120 – $160 yearly depending on the weight of your dog.  There are multiple types of prevention medication available for either topical or oral administration.  Some are also combined with flea preventatives to eliminate the need to give two different medications.  Whichever you choose, it is important that they be given once monthly (ever 30 days) during the mosquito season to work properly and ensure your pet is protected from heartworm disease.

Heartworm disease testing starts April 15th  2013.  Please call us at (905) 385-5354 to book your dogs appointment or to discuss any further questions.

Click here to read more about Heartworm Disease

Click here to watch a video interview with Dr. Rubin of the American Heartworm Society discussing heartworm disease.


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