Tuesday, June 6, 2023



RV Pet Vet: Heartworms in pets: bad news, even deadly

Ask the RV Vet

With Dr. Deanna Tolliver, M.S., DVM

Occasionally I forget to take a daily vitamin pill. And I may forget to set out the trash to be picked up. But there’s one routine I don’t forget: I always remember to give my dogs their monthly heartworm prevention.

I remember because it’s vitally important and potentially fatal. Okay, so there’s also the reminder sticker I put on my calendar ahead of time, but regardless…..I make sure they get it.

LATEST PET RECALLS:  This week marked the biggest number of dog and cat raw food recalls in many years. Is your pet food on the list?

No matter where you live, your dog and cat are at risk of getting heartworms: they’ve been found in every state except Alaska.

As the name implies, these are worms that live in the hearts of dogs and cats. They can be up to a foot long! How they get them is an almost unbelievable, but it happens every day. Here’s the story:

Female heartworms that live in a dog’s heart produce baby worms. The technical name for them is microfilaria, and they circulate in the dog’s bloodstream. Here’s the crazy part: when a mosquito bites the dog, it picks up these baby worms, which further develop IN THE MOSQUITO. Then, a couple of weeks later when the microfilaria have matured, AND the mosquito bites another dog, the baby worms are deposited on the skin of the second dog, and they migrate through the mosquito’s bite wound.

After about six months, the baby worms become adult heartworms, and they take up residence in the dog’s heart. The adults can live for 5-7 years in a dog, and 2-3 years in a cat. They don’t live as long in a cat because cats are not their natural host, as dogs are. So in cats, most heartworms don’t live long enough to become adults.

Dogs can die from heartworms. They can die even when treated if they’ve been infected for a long time. Not only is the heart damaged, but the lungs and arteries can also be affected as well. Symptoms can include a chronic cough, tiredness, decreased appetite, and weight loss.

You can prevent all of this from happening to your dog, and cat, by giving them a preventative “treat” every month. In typical cat fashion, some cats, and some dogs don’t like the “tasty treat” and owners may have to cut the pill/chew into smaller pieces and hide it in food, for example. When you buy a box of prevention, you also get a sheet of reminder stickers to put on your calendar ahead of time.

Heartworm prevention is by prescription only from your veterinarian, and all dogs and cats must be tested before taking it. Here’s why: if you gave it to a dog that had heartworms, it’s possible that all those hundreds of thousands of baby worms would be killed. That could set up an anaphylactic shock situation that could kill the dog.

Even if you are certain you have given the prevention every month, it is still wise to get your pet tested every year. It is rare, but some pets still get infected in spite of being on prevention. 

There IS a treatment for dogs that get heartworms. It can be expensive but is usually effective. Part of the treatment includes keeping the dog quiet for a month or more, and that can be the most challenging part of treatment.

Unfortunately, there is no treatment for cats, but the disease can be managed. If a cat stays on prevention every month, the adult heartworms usually die after two to three years. During that time, however, there can still be damage to the heart and lungs. 

As RVers, we often travel to areas that may expose our pets to potential dangers. Your dog and cat are not safe from heartworms until they have been tested and put on prevention.

C’mon…..have a heart and put your (pet’s) heart in the right place. Test and prevent heartworms!

Did you miss my last column on microchipping? If so, click here.

Dr. Deanna welcomes your questions. Email her at YourRVvet@gmail.com 

Dr. Deanna Tolliver has been a full-time RVer for over 3 years, although she has been an RVer for several more. She travels with a fifth wheel and a 1-ton dually truck. Her travel companions include 4 small dogs (Tootie, Chiquita, BooBoo, and Janie), and a 36-year-old Yellow-Naped Amazon Parrot named Toby. She has a BS and MS in biology and zoology, respectively, and a Doctorate of Veterinary Medicine from the University of Missouri, Columbia. She owned a veterinary hospital for many years and recently handed over the reins to a new owner. 


0 0 votes
Article Rating
Subscribe to comments
Notify of

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Inline Feedbacks
View all comments
5 years ago

Thank you, I always wondered heart worm prevention was such an issue. I see why Mosquito vector control is important

5 years ago

My understanding is the HW takes at least 4 months to be a problem, so administering the treatment every 3 months is effective.

Dr. Deanna
5 years ago
Reply to  teubner

First, let’s get the terms straight: the pill or chewy that is given every month is prevention; if your dog has heartworms, it gets a treatment. Giving the prevention every 3 months is NOT effective. The part you don’t know is that the prevention works retroactively. In other words, when you give the prevention, it is killing any microfilaria that are ALREADY in the dog. In the three months in between prevention, many microfilaria could be present, and, they could be in different stages of development, making it more difficult to kill them all, and lead to adult heartworms.
The recommendation by the American Heartworm Society—and I encourage you to go to that website—is that prevention be given every month. To fully protect your dog or cat, you are just going to have to trust the veterinary community on this issue. If you second guess the professionals on this, you are putting your pet at risk.

5 years ago

When we travel we put our dogs on a heart worm regimen. We live in Ut and don’t have a real problem here.

Dr. Deanna
5 years ago
Reply to  Bill

Hi Bill,
Good job to put your dogs on heartworm prevention while you’re travelling.
I imagine it’s easy to not worry too much about heartworm in UT, but The American Heartworm Society thinks differently. I’ll just quote here from their website:
“Thinking that your companion animal is protected because you live in the desert is false security. The lower likelihood that pets are protected from heartworm in desert regions makes the presence of just one heartworm-positive dog or coyote in a neighborhood a serious concern.”

Linda and Rick
5 years ago

Living in Washington state, we only use heartworm meds when we travel. Two years ago we picked up a rescue dog in Oklahoma who, after we got home and took her in to be spayed, tested positive for heartworm so I can vouch for the lengthy process it takes to get rid of them! Way cheaper and safer to just not get it in the first place.

***LINDA and critters**

Dr. Deanna
5 years ago
Reply to  Linda and Rick

Hi Linda,
First of all, thank you taking in a rescue dog!
You may already be aware, but some dogs have tested heartworm positive in WA. Many of these were rescue dogs transported to WA after Hurricane Katrina. But…..this means that heartworms are in WA. There may currently be only a few very small pockets of mosquitoes that carry the microfilaria, but to me, that is reason enough to keep my pets on prevention year-round. I’ve always been amazed at the idea that ANY dog or cat could get heartworms. What are the odds that the mosquito that is carrying a baby heartworms would not only bite my dog, but that they would develop in to a full blown infection? Pretty good, apparently, judging by the increasing numbers we are seeing every year. And FYI, Washington is now listed as one of the states where heartworm rates are on the increase.

5 years ago

What are the symptoms of heartworm? Cats and dogs.

Sign up for the

RVtravel Newsletter

Sign up and receive 3 FREE RV Checklists: Set-Up, Take-Down and Packing List.