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Over Wintering – Heartworm Disease in Colorado

By: Dr. Barbara Caldwell

November 17th, 2022

The leaves are falling and the weather is turning colder. Heartworm disease isn't a concern any more, right? Unfortunately, that is not true. Mosquitos are found in the Denver & Front Range areas throughout the winter months and still have the potential to spread dangerous and deadly heartworm disease. It is important that your pet be protected by using a year-round preventative product such as the monthly chewable tablets, Interceptor Plus or have your veterinarian administer the 12-month protection, Proheart-12.

In Fall, mosquito species that die off for the winter will not disappear until after a good freeze, although they become less active as temperatures drop below 50 degrees. For those mosquito species that hibernate as adults, they become dormant when winter temperatures arrive, but will come out anytime the weather is warm enough, generally when the temperature rises over 50 degrees. Think about those great, sunny, 60–70-degree Colorado winter days. Also, these hibernating mosquitos are cold-blooded insects that have a great knack for finding warmer areas to survive in. The urban heat island effect has been found to be a significant way mosquitos extend well past their normal “season.” Heat that is retained in buildings, parking structures and other protected spaces such as the inside of houses, sheds, garages and barns, all allow these annoying little pests to thrive even when the thermometer begins to dip.

Avoiding the on-again, off-again preventative schedule ensures that our pets are always protected. The savings of stopping preventative for a few months doesn't compare to the over $1,000.00 treatment cost once a pet is positive for heartworm disease. Additionally, since the heartworm preventatives are broad spectrum and protect against multiple parasites, such as intestinal parasites, fleas, and ticks, we can prevent the increase of other parasitic diseases. Discontinuing the parasite preventive because the summer has passed, puts our pets at risk.


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