Boulder Veterinary Hospital (303) 442-6262 Heartworm

Boulder Veterinary Hospital

3630 North Broadway
Boulder, CO 80304


What is Heartworm Disease?

        Heartworm disease is a serious medical condition caused by a parasite named dirofilaria immitis. Dogs are infected with this parasite via bites from infected mosquitoes. Developmental stages of the parasite develop in the blood stream and result in large worms in the great vessels and chambers of the heart. These large worms can cause many symptoms of disease with clinical signs of lung and heart disease.

But, I was told we don't have heartworm disease in Colorado.

        While it is true that the prevalence of heartworm disease is much lower in the state of Colorado than places like the east coast or the southern states, Colorado is considered a red state by the American Veterinary Medical Association (AVMA). This means that mosquitoes in the state of Colorado do carry the developmental stages of the heartworm parasite and we do see infections in Colorado. Boulder is also a very global community in our opinion and we see animals from all over the world moving into our community on a regular basis. Therefore, we at Boulder Vet feel it is a prudent measure to administer heartworm preventative to your dogs.

What happens if my dog gets heartworm disease?

        Heartworm disease is a very serious condition that can result in the death of your beloved pet. Treatments for heartworm disease do exist and involve 2 injections of an arsenic compound into the muscle of your dog. After administration of the arsenic compound your dog must be kept in a cage and only allowed out to defecate and urinate on a leash for approximately 6 weeks. The reason for this is that the medication kills the adult worms which can then dislodge and cause obstruction of major vessels of the body or the lungs resulting in severe clinical signs and potentially death of your pet. Treatment for heartworm is very difficult on you and your pet and is quite costly. It is because of all these reasons that we strongly recommend prevention of heartworm disease.

How do I prevent heartworm in my dog?

        Heartworm prevention is extremely easy! Heartworm preventative is a once monthly tablet given to your dog during mosquito season (spring through fall). It is usually a beef flavored chewable tablet that your pet will eat like a treat. As an added benefit, the heartworm preventative also contains a small amount of dewormer so that if your dog ingests a roundworm or hookworm egg it will prevent a significant infection from occurring.

I was told heartworm preventative isn't safe for my herding dog.

        Some breeds of dogs related to collies can be extremely sensitive to Ivermectin, one of the medications used to prevent heartworm disease. There are other medications than Ivermectin available and we will gladly prescribe one of them for your pet if you are concerned or we feel it is in your pet's best interest. The dose of Ivermectin in most heartworm preventatives is extremely low and Australian shepherds, cattle dogs, and other non Collie herding breeds are extremely rarely affected negatively by this low dose. Sensitivities present themselves as tremors which are almost always reversible by discontinuing the medication. Since there are other medications other than Ivermectin available there is really no reason to not administer a preventative to your dog.

Why does my dog need a blood test before starting their heartworm preventative?

        A blood test is needed in all dogs over 6 months of age prior to beginning a heart worm preventative. The medication used to prevent heartworm is very different from the one used to treat heartworm positive dogs. Administration of a preventative to a heartworm positive dog can have negative consequences that we avoid by testing your dog. Dogs on year round preventative should be tested every other year. Dogs on seasonal preventative should be tested annually each spring before beginning the medication. Annual costs end up pretty similar and the choice is yours. Personally, I have a hard enough time remembering to give the medication once a month during mosquito season so it's nice to take the winter off.

What about my cat?

        Currently, heartworm disease in cats does not appear to be a problem in Colorado. Veterinarians in Texas are currently recommending heartworm prevention in cats since as few as 1 worm can have a very negative impact on your feline friend. We pride ourselves on being as current as possible when it comes to emerging infectious diseases in our state and will let you know as soon as any recommendations are changed.


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