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Tiger Mosquito - HearwormHeartworm is a parasite that is passed to dogs from the bite of an infected mosquito. The mosquito injects baby worms (larvae) into the blood stream and these larvae mature through several life stages until, six months later, they grow into adult worms which live inside the blood vessels of the lungs and the chambers of the heart itself.

In heavy infections the heart and lung vessels can become physically clogged up with worms resulting in lung disease, heart failure, and death. Heartworm infection can be PREVENTED by giving a once-a-month chewable medication that kills the baby worms (larvae) before they can mature into adults and cause disease.

Heartworm disease is something that many clients don't understand, so let's clear things up...

Heartworm Life Cycle - American Heartworm Society (AHS)

My dog doesn't go outside so I don’t need to worry about heartworm disease.

Dogs get heartworm disease from mosquito bites, and mosquitoes don't pay particular attention to inside versus outside. In the time it takes you to open a door to step into your home a mosquito can fly inside. Even "indoor" dogs are at risk of contracting heartworm disease.

My dog doesn't have any worms in his stool so I know he doesn't have heartworm disease.

The worms that cause heartworm disease live within the blood vessels of the heart and lungs, and DO NOT live within the intestinal tract. The stool sample that is run once per year checks for intestinal parasites. A blood sample is used to check for heartworm disease.

My dog doesn't need to be on heartworm prevention every month because mosquitoes aren't out in winter.

If New England winters were consistently cold every single day this might be true, but our weather is notoriously unpredictable. Just this year (2017) Boston experienced record highs of 73 degrees in FEBRUARY! It doesn’t take many days of warm weather for mosquitoes to be out and about, and we don't recommend that you take your chances given the severity of disease and cost of treatment.

Only dogs in heartworm epidemic regions (like the Southeastern United States) need to be on prevention.

This is a simple falsehood. The American Heartworm Society estimates that anywhere from 6-25 dogs are diagnosed with heartworm disease in Middlesex county each year PER VETERINARY CLINIC. This figure subjectively sounds in-line with what we experience at Ashland Animal Hospital. Heartworm disease is unquestionably present in our area!

US Heartworm Incidence Map 2013 - American Heartworm Society (AHS)

I don't like to give my dog chemicals, so I don't use preventative medication.

Heartworm preventative products are far safer for your dog than the injectable medication required as part of heartworm treatment for a positive dog.

For more information about heartworm disease, including prevention and treatment please visit the American Heartworm Society.

Dr. Melissa Bisesi joined the Ashland Animal Hospital team in November 2015. Her medical interests include diagnostic imaging (abdominal ultrasound), nutrition, and formulating patient-specific weight management plans. Visit Our Veterinarians page to learn about Dr. Bisesi and our other veterinarians.