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Heartworm Testing

Heartworm disease is caused by the parasite Dirofilaria immitis and carried by infected mosquitoes.  Historically, heartworm disease was not seen in Colorado or was very rare, due to the fact that we have a very dry climate, cool temperatures, and a short mosquito season at higher altitudes.  The increased travel of dogs from other areas of the country, especially the southeastern U.S., has contributed to its presence here. In fact, according to the Companion Animal Parasite Council, 1 out of 146 dogs in Colorado tested positive for heartworm in 2015, and that number is already on the rise in 2016.

Mosquitos infected with the parasite Dirofilaria immitis may transmit Heartworm disease to your dog if it comes in contact with your pet. The microfilariae (small, immature heartworms) develop in the mosquito and are deposited with saliva on the dog’s skin as the mosquito is feeding.  The infective larvae pass through the skin and migrate through the body tissues, where they grow into adult heartworms and damage the heart.  We recommend testing for heartworm infection before beginning preventive medication and at then yearly after your dog is on medication.  The test can be performed in our clinic and takes only a couple of drops of blood and a few minutes for the results.  Many dogs infected with heartworms may not show any evidence of infection in the early stages of the disease.

You can find more information on Heartworm disease by visiting the American Heartworm Society at

You can also find more information on Heartworm prevalance, specific to your Colorado county, by visiting the Companion Animal Parasite Council at