Canine Heartworm Disease

Dr. Brian Brumfield

Rogers Pet Clinic- Contact Us

What is a common misconception about how heartworm disease is transmitted?

A very common misconception with heartworm disease is that a lot of people assume it can be transmitted from other dogs. That's not the case, it's transmitted through mosquito bites directly. We see quite a bit of mosquitoes here in Minnesota; so it's very important that we talk about heartworm disease and try to keep all of our pets protected against it.

How long does it take for a mosquito bite to result in heartworm disease in a dog?

Once a dog is bitten by a mosquito, it takes approximately six months for the larva from the mosquito to develop into an adult heartworm. So about 6 months after they've been exposed through a mosquito bite is the earliest a dog could possibly test positive to heartworm disease. Once it becomes an adult heartworm, it becomes very difficult to kill with any oral medication that we have.

Why do you recommend yearly testing for heartworm disease?

We recommend yearly testing because it takes several months for them to develop clinical signs and it takes several months for them to even show up positive after they've been exposed.

How can heartworm disease be prevented?

There are a lot of different products on the market for heartworm prevention. Here at Roger's Pet Clinic, we prefer Simparica Trio, which does a fantastic job at preventing heartworm disease. We also have Heartgard in clinic as an option as well.

Any of the larvae before they get to six months of age can be killed with that monthly preventative pill that we're giving. And so the longer that worm is allowed to mature, the the harder it is to kill. So that's why giving monthly heartworm prevention is really important.

If you give it on time every month, it's very effective at killing that larva in the bloodstream.

What issues do you see with people administering heartworm prevention?

People often stop giving heartworm prevention in the winter months, which can be an issue. If a pet is bit by a mosquito in November and you gave the last dose of heartworm prevention in November, the larvae will thrive and develop into a mature adult worm over the winter. Then, in the spring, you have a heartworm infection that we have to treat with more expensive and aggressive treatments. So, for that reason, we really encourage owners to give heartworm prevention year-round to protect their dogs.

What about heartworm disease in cats?

Cats can get heartworm disease as well. It's hard to test them for it, so it's important if your cat has any mosquito exposure whatsoever, even if they're indoors only sometimes, that they are on monthly preventatives. Revolution is the product we recommend for your cat.

If you have any other questions, please give us a call at (763) 428-8688. You can also email us at and we will get back to you as soon as we are able. Don't forget to follow us on social media: Facebook and Instagram