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What is Heartworm and How Worried Should Dog Parents Be?

J'adore un Labrador, Retriever, Black Dog

Each of our dogs received one dosage of heartworm when they were puppies.  They haven’t been treated with heartworm medication since.  I spend a lot of time on websites dedicated to dogs and this time of year we see a lot of ads for flea and tick treatment (I choose non-toxic brands) and heartworm medication.

The other night we were outside with the dogs, doing our evening walk on the property, and my boyfriend says “there are too many mosquitoes out there,” and heads inside.  I look down at Rodrigo and he has 5 on his coat – I wave them away, take them  inside and spray them with the Bright Eyes Pet Wellness, which repels fleas, ticks and mosquitoes.

That’s when it hits me…

  • Heartworm is a danger for our dogs!
  • What the hell is my problem?
  • Why hasn’t my veterinarian brought it up?

It was late, the vet’s office was closed, so I went to my trusted friend, Google – this time I stayed away from the forums.

What is heartworm?

I was going to copy and paste from another site, but I hated the explanation.  I need simple and clear when it comes to the health of our dogs.  A heartworm is a parasite, a wormy-parasite that lives in the heart and pulmonary arteries of an infected dog.  They get it from a mosquito bite, the larvae travels through the blood stream to the heart.  It can be fatal, but a dog can live from 5 to 7 years after being infected.

How worried should dog parents be about heartworm?

It seems to depend on where you live.  I spoke with a few local veterinarians (I live in Washington state) and the only cases of heart worm that they’ve seen were in dogs that either moved from another state or traveled into another state.  They say that the reason our dogs are safer (not safe, just safer) is for many reasons (all suppositions)…

  • Our climate and cold winters that kill off the mosquitoes
  • Our proximity to the Sound and Pacific Ocean
  • The mosquitoes that cause heartworm haven’t migrated here yet – “yet” is the key here

“The disease has been seen in every state except Alaska, but is most common in or on the East Coast, southern United States and Mississippi River Valley.” ~ ASPCA

Check out THIS informative article over on Dr. Becker’s site.

What dog parents can do to prevent or treat heartworm?

If you live in a high risk area or are just concerned, don’t order and administer heartworm medication to your dog.  Doing this can cause a severe, negative reaction.  Instead, call your vet and schedule a test.  If your dog is heartworm free, you can then discuss prevention.  If your dog has heartworm, then you discuss treatment.

If you plan to move or make a trip with your dog to the East Coast, southern United States or Mississippi River Valley – talk to your veterinarian about treatment before you go.

Symptoms of heartworm…

“Labored breathing, coughing, vomiting, weight loss and listlessness, and fatigue after only moderate exercise. However, some dogs exhibit no symptoms at all until late stages of infection.” ~ ASPCA

Heartworm Medication Recall

With the recent news of heartworm medication recalls, it’s tough to know what to do.  ProHeart 6 was recalled in 2004 and when I started blogging, I read a heart breaking story of a dog who died after a dosage (and there’s also a comment of another dog parent’s experience – so sad).  And most recently Iverhart Max was recalled, which makes me wonder if there’s a holistic solution for dog families.

I found this article by Dr. Becker where she shares my discomfort with chemical flea/tick/mosquito repellents.  Like with Canine Parvovirus, there are tons of claims of a cure by many people and I have a feeling that many of them are frauds.  So I think it’s important to at least speak with a veterinarian about prevention and treatment, because we’re always coming up with something new and what may not work for one dog may work great for another.


Have you tried any alternative routes to prevent and/or treat heartworm?


  1. Living in a Southern state, it’s imperative to continue your pet’s heartworm medicine year round. Our rescue organization pulls pups from the shelters that have heartworm and they are treated. It does take some time and the pup is usually limited to his/her activities for that length of time. When something is preventable, people should definitely take advantage of prevention. The cost for treatment is much more than the prevention and also limits the pup’s activity level for quite some time. We use Trifexis, it’s made to repel and kill ticks, fleas, heartworm and intestinal worms. It’s a bit pricey, but we know we are doing what’s best for our pups!

    • Thanks, Jeanette

      I feel so lucky that today, this isn’t a worry, but I don’t want to be complacent and will always keep an eye out for when this changes. Someone told me that drought, harsh or mild winters, or hurricanes can switch things up for all of us when it comes to fleas, ticks and mosquitoes.

      Thanks for stopping by; how often do you give them Trifexis – is it once a year?

      • Trifexis is a once a month pill. It’s supposed to taste good so they’ll want to eat it.. but my picky pups must have them given in an alternative way (stuck down their throat). Yep, we’ve tried pill pockets, peanut butter, lunchmeat, etc.. all gets eaten except the pill!! lol

        • Thanks for sharing! Sucks that you can’t sneak it into something. As long as I use the right about of peanut butter, then I’m golden 😉

  2. Hi Kimberly,

    Saw your post on your Google+ page – it’s a good read (as always), and thank you for bringing up a very important topic. And thank you – a million times over – for stressing the difference between “safer” and “safe”! This is truly an important distinction – especially when I hear “pet safe” used in conjunction with things like snail & slug bait and/or deicers, etc.

    Anyway, heartworm disease is legit and a significant killer in certain parts of the country. But with pets traveling and being displaced (typically as a result of natural disasters) with greater frequency these days, as well as the shifting weather patterns, pretty much all dogs are at increasing risk. And given the severity of the condition, it’s just not worth taking the chance. Add to that the fact that most of the heartworm preventatives also help to prevent and treat common intestinal parasites, and it’s a lot of “bang” for the proverbial buck. When I was in the clinic I recommended preventatives to all my clients, and all-year around, too (intestinal parasites, as you likely know, are extremely common here in the Pacific NW).

    Here’s a good resource for heartworm disease: Yes, it’s sponsored by many of the big pharma companies who make preventatives, and thus have a financial stake in their use, but it does have great info.

    Hope this helps. And hope you had a great time at BlogPaws :-)


    • Had an amazing time at BlogPaws and thank you so much for that resource. As a dog parent, it’s so hard to separate what’s good information I need to know and what’s a commercial. As a blogger, it’s my job to really delve into the facts, because it’s for the safety of my own dogs and anyone who reads my blog. It’s interesting how so passionately push us to avoid these medications, siting dogs who have horrible reactions, while there obviously is a problem. I keep reminding myself that people who are happy forget that we need their story too so that we can better make an informed decision about our dogs health and happiness.

      Ooops, I think I just stumbled upon a blog post! LOL

      Thanks for stopping by! I love having a vet commenting.

  3. In my area (North Dakota), vets typically recommend the year-round monthly treatment, which I believe is too aggressive. I have typically given the medication to my dog only during the warmer months. This year I plan to give the medication even less often as his risk of actually contacting heartworm is very low. As you said, it all depends on where you live and other factors.

    • Thanks for stopping by, Lindsay and THANK YOU for sharing your article, I’m heading over to read it right now. We have three active dogs and the idea of them being limited due to heartworm is heart breaking. We already have to deal with joint pain when they over do it :(

  4. Great post Kimberly. In Texas, heartworm is a big deal. Even cats get it. Sounds like you are pretty safe where you live though. We always like to promote heartworm prevention because treatment is awful and expensive. The treatment for a dog with heartworms is injections of arsenic into their back muscles. And then they can’t be active for a month. Sucks. There’s no treatment for cats.

    Ivermectin is pretty mild and as a dewormer I think. Basically, it just deworms your dog once a month. I’ve never seen any reactions to it, but I know it’s possible. Proheart was not a good drug at all… although it was a bit before my time. People just liked the convenience of it since it was a 6 month thing.

    Pug rescue that we used to work used a homeopathic treatment for their heartworm positive dogs, although I’m not sure what it was.

    • Thanks for weighing in, Ann
      I think the news about ProHeart frightened many people away from heartworm medication.

      What flea & tick treatment do you recommend?

      • Advantage multi is good for fleas, ticks & heartworms & intestinal parasites if you’re looking for an all in one thing. I know so many people are scared of the topical treatments these days though. I like heartgard or iverhart for monthly HW prevention myself (doesn’t do fleas). I’ve been doing some research on neem oil lately which is supposedly an all natural bug repellent. I wouldn’t use it to replace heartgard though.

        • Thanks! I’m thinking of going topical this year, because we had such a mild winter. Our dogs never had a reaction in the past, so I’m sure we’ll be fine.

  5. Here in MN we take it seriously with a yearly test and we choose the year round treatment. I have always had heart worm medications for my dogs but when we lived in Germany for 10 yrs they did not use them as they did not have heart worm cases and I have to say it felt weird to me but we survived and got right back on the medications once we were back in MN. I guess I don’t worry so much about these treatments, but I really hate putting Frontline on my girls. We have so many ticks I don’t know what else to do and it is doubly frustrating since they still get ticks now and then.

    • I feel the same about Frontline. I’m just note comfortable with it, but I don’t know what my options are, because I’m concerned about the heavy flea season that they’re anticipating and I don’t know if our natural option can stand up and I’m not sure if I want to test it out on our family.

  6. Thank you for writing this article on heartworm…the timing is perfect. I just moved from Dallas to Southern California. My dogs have always taken preventative for heartworm…but no one here seems to use it. Now I understand why. Thanks!

    • Glad I could help, Corinna! I crossed this off my list and now I have to tackle fleas and ticks.

  7. Excellent information, Kimberly! (as usual!)…I was going to comment till I read the comments, which expressed my feelings better than I could have. Here in Texas, witht the humidity and standing water (if it ever rains, that is), heartworm preventative is essential. I used Revolution for years on Monty and Rosie (RIP 2011) with no ill effects, and now Dakota gets it too.

    • Thanks for sharing the brand, Deena!

  8. P.S. I tried to share this on Facebook but it wouldn’t share.

    • My site was down for about 45 minutes earlier, that may have been a residual of the problem. I just shared and it’s back to normal.

  9. I’m in the Ohio area and heartworm preventative is recommended year-round. I’ve also fostered many heartworm postitve dogs while they undergo treatment for the disease. It is not pretty! The drug used to treat the disease is immiticide and it is a form of arsenic. Talk about toxic! Once they start the treatment, they need to be on strict exercise restriction – leash walked for potty breaks and crated in the home if you have no way of keeping them from playing or getting super excited. Treatment can take up to 2 to 3 months (exercise restrictions throughout the treatment process) and can easily cost thousands of dollars. Once the treatment is done, you wait 6 months and have the dog retested for heartworm, and yes, it is possible that the dog will still have the disease and have to undergo another round of this grueling treatment. There are dogs that are so badly infested that they do not survive treatment. Most vets will recommend euthanasia, rather than attempt to treat a dog that is badly infested. If the disease is left untreated, then there is no good outcome for that. Our rescue had to euthanize a dog last year because he was already in heart failure. He never would have survived treatment. He was only 5 years old. We currently have a HW positive dog that cannot start treatment because he has elevated liver values. He’s on meds to try and bring the values down. If it’s successful he can start treatment, if it isn’t, his future isn’t very promising. Needless to say my dogs are on preventative all year long. It’s much cheaper in the long run, and in my book the “safer” option.

    • OMG, Steph – thank you so much for sharing this. Do you happen to have a preferred heartworm medication for the year-around prevention?

      • My dogs are on Sentinel. Sentinel also deals with fleas and certain intestinal worms. I’ve also used Trifexis before too, but that one smells nasty and the dogs won’t readily eat it. Trifexis also protects against intestinal worms and fleas. It provides better flea protection than Sentinel. A word of caution to anyone that owns a Collie or certain other herding breeds…Ivermectin is not tolerated in those breeds. Ivermectin is the active ingredient in Heartgard and some other heartworm preventatives (not in Sentinel or Trifexis). You can read up about drug sensitivities and the breeds affected at this site:

  10. Heartworm is one of the things I’m not taking chances with. The product I was using for Jasmine was reasonably benign and JD is now on Heartgard. Spending a lot of time outdoors, in the woods and farmland, mosquitoes are everywhere. And there have been cases of heartworm positive dogs in our region, and not just those that had been brought from down South.

    We do use natural sprays to keep mosquitoes away but we do use HW preventive. Risk vs reward scenario? The risk of HW is too high to take chances.

    • That’s interesting, Jana – what area do you live in?

  11. I just got a question from a reader about this tonight so I did some more research myself. I don’t know if you are from Washington but I never remember it being a pressing issue so I was curious. I guess it takes a long time for the parasite to grow in a pool of mosquitoes and the consensus seems to be that the mosquitoes don’t live long enough here….which you found in your research but stated more clearly here.

    • Yep, that’s what I learned. I’ll keep an eye on the news just in case this changes, but I’m thankful to have one thing taken off my list of things to worry about for now :)


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