Top 10 Things to Know about Heartworm Disease

by Dr. Meg Warner, DVM

It is April.

It is almost Spring.

It is Heartworm Awareness Month!


We are excited to see things turn green, buds to open and flowers bloom! We also know it will not be long before our favorite Minnesota “bird”, the dreaded mosquito, will be buzzing in our ears. So, we start to think about the diseases that they transmit!


For our pets a HUGE concern is HEARTWORM Disease.


Here are the top 10 things we need to know about this mosquito borne disease that affects dogs and cats.

  1. Heartworm can be fatal and is caused by foot-long worms that live in the heart, lungs, and associated blood vessels of the affected pets, causing severe lung disease, heart failure, and damage to other organs. Heartworm disease affects dogs, cats, and ferrets, as well as other mammals including wolves, coyotes, and foxes.

  2. Heartworm is transmitted by mosquitoes. Adult female heartworms living in an infected mammal produce microscopic, immature worms called microfilaria that circulate in the bloodstream, and when a mosquito bites and takes a blood meal from an infected animal, it picks up the microfilaria. They develop and mature in the mosquito into an infective stage and then are transmitted to other mammals when the mosquito bites again.

  3. Heartworm is found in all 50 states and many parts of the world. Both indoor and outdoor pets are at risk of exposure.

  4. It takes 6 months for the larvae to mature to an adult heartworm. Adult heartworms can live for 7 years.

  5. Would I know if my pet had heartworm? The early stages are typically asymptomatic and require blood testing to detect. Once the disease has progressed, symptoms can include a mild persistent cough, reluctance to exercise, fatigue, decreased appetite, and weight loss. Some pets also have a swollen belly.

  6. Prevention is simple and effective! Even if treated early, the disease can cause permanent damage to the heart, lungs, and other organs. Prevention is far better than treatment.

  7. Prevention is recommended 12 months of the year. There are several FDA- approved heartworm preventatives available in many formulations. Your veterinarian will recommend what is best for your pet.

  8. Blood testing is recommended before starting prevention. Prevention does not kill adult heartworms if an infection is already present, therefore, a blood test is recommended before starting prevention, 6 months after starting and annually thereafter.

  9. Talk to your Veterinarian. Your veterinarian can help you find the best preventative for you and your pet.

10. No really–Talk to your Veterinarian! Don't delay getting your pet started on heartworm prevention.


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