Heartworm disease is often discussed as an ongoing risk for dogs and cats. The reality is that the risk depends greatly on the geographic location and lifestyle of pets and people. Let’s start with a few facts:
- Heartworm disease is caused by a worm that lives in the blood vessels around the heart.
- Heartworm disease must be spread by a mosquito and cannot be transmitted directly from pet to pet.
- The risk of heartworm disease is directly dependent on mosquito exposure and environmental temperature.
- Heartworm preventatives are not benign medications, and true risk to your pet should be considered before administering them.
The risk of heartworm disease will be higher in warm, humid environments. The larvae cannot mature in the mosquito unless the environmental temperature is 57degress or above for at least 3 weeks. Once the temperature drops below 57 degrees, the development of the larvae stops. This makes heartworm even less common in dry climates due to low nighttime temperatures. Mosquitoes may still be present in the lower temperatures, but there is no risk of heartworm disease.
We recommend using heartworm preventatives based on your pet’s risk of exposure and do not make general recommendations for all pets. If your pet swims regularly in outdoor lakes or ponds, then its risk is higher than a dog that spends its time primarily indoors.
For more information about preventatives, please refer to the “Keep the Bugs Off your Pet” PDF, found in the Home Treatments section of our Resources page.
