Six months of Heartworm prevention (through the warm months) for dogs, used to be
what most people did for their dogs here in Colorado. Recently, many factors have influenced a
change in thinking about this procedure, necessitating more wide spread twelve month protocol.

Irregular Weather
First, it is becoming harder and harder to estimate when mosquito season is upon useven
in Colorado where seasons seem to come and go fairly regularly. Year-round prevention
also helps if you travel to other parts of the country; however irregularly that may be. Both can
leave your pet vulnerable to transmission at times when you wouldn’t expect to have to give your
dog prevention.

Complicated to Treat
This leads us to the next issue- heartworms are sneaky. They have a complex lifecycle
and pet-owners are usually not aware their pet has been infected until it is too late. Heartworm
preventatives actually kill certain stages of the baby worms before they can grow to adults.
However, only the presence of an adult worm will cause a dog to test positive. It is actually
possible for a dog to test negative and still be in the early stages of infection. Therefore, it is
important to test every year and continue on the preventative again promptly.

Heartworms are Becoming More Resistant and More Prevalent
New studies show that, while 20 years ago one dose of preventative would have killed
100% of the baby worms present, now it may take more than 1 dose to rid a dog of the infection.
In the U.S., over 250,000 cases of Heartworm are reported every year. Remember, these are only
reported cases and the actual number may be much higher.

Added Benefits
Heartworm prevention also controls intestinal parasites all year long. These worms not
only affect your dog, but can affect your family.

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