Heartworm Symptoms – Canine Heartworm Medicine and Prevention For Your Dog

Heartworms, officially known as Dirofilaria Immitis– are internal parasites that can infect small animals such as dogs, cats, raccoons, foxes, coyotes, ferrets, and wolves.

You don’t want to wait for your pet to show heartworm symptomsCanine heartworm medicine is highly toxic and it’s best to use prevention….as the #1 line of defense.

Cases are reported in all 50 states….so no place in the US is completely safe year round.

Before buying heartworm medicine – these are the things to know to make a well-informed decisions.:

  • How heartworm parasites are transmitted and how to break the life cycle
  • The REAL risk to your pet based on your “mosquito season”
  • Symptoms of heartworm disease
  • Benefits and drawbacks of prescription heartworm prevention treatments
  • Benefits and drawbacks of natural heartworm prevention treatment
  • The #1 FREE thing to protect your pet.

How Your Dog Gets Infected – Heartworm Disease Transmission

Heartworm prevention is a necessary health consideration for pet parents. Get the facts to make an educated decision and help increase the odds of a happy healthy life for your pet.

This highly infectious disease is spread by mosquitoes which inject heartworm larvae when they bite your pet. This early stage of the parasite (microfalaria) moves through your dog’s blood system and finally settles into the heart tissue where they grow to adult worm form in the right chamber of your dog’s heart.

If both male and females worms are present they can reproduce. Full blown heartworm disease can show as many as 300 worms in the dog’s heart.

While your dog is infected with larvae in his system other mosquitoes can pick up the infected blood by biting your dog and then pass the disease on to other uninfected animals.

Heartworms can cause serious health problems including heart failure (and death). Recovery treatments can be painful for your dog and expensive. This is a deadly disease and will be fatal to your pet if left untreated. They key factor in the cycle of this disease is “the mosquito”. It takes about 6 months for the larvae to travel to the heart and develop to the adult stage (6 stages in the growth cycle).

Symptoms of Heartworm Disease in Dogs

  • Lack of energy
  • Loss of appetite
  • weight loss
  • coughing
  • collapsing
  • respiratory problems
  • depression
  • no desire for exercise
  • vomiting

Heartworm Prevention Treatments – Prescription vs Natural

Let’s be clear on heartworm prevention. Monthly medicine prescribed by your vet does NOT prevent this disease.

The heartworm prevention is a chemical poison (the monthly chews like Heartgard, Advantix, Sentinel, and Interceptor) that kills any heartworm larvae your dog may have been exposed to (by the bite from an infected mosquito).

You are killing the larvae (if present) – not preventing your dog from getting exposed to the disease carrying parasite.

Some form of preventative prescription treatments are “multipurpose” which treats for other forms of worms and parasites.  Using these products will protect your dog from heartworm larvae but you are over medicating your dog by treating for these other parasites that your dog probably doesn’t have.

Personally I recommend only using a preventative medicine that targets heartworms only. Why subject your pet to other chemicals if it’s not necessary?

These are medications that your veterinarian must prescribe for you to be able to buy for your pet….whether buying them at your dog’s clinic or online it will require a prescription to make a purchase.

The good part is that these drugs will kill the heartworm larvae and it will be breaking the life cycle of the parasite. The downside of these meds is that they are slowly poisoning your pet.

I believe in opting for natural solutions for my pets but heartworm prevention is serious. There are herbal and natural remedies out there but they also come with concerns.

Many natural heartworm treatment options include “black walnut” and “garlic” as ingredients which the Pet Poison Hotline has listed as “toxic” items to dogs.  But remember the conventional treatments (prescription meds are just as deadly).    Black Walnut is viable herbal treatment but your will need to proceed with extreme caution.

Going with a natural treatment avoids the chemical exposure present with prescription drugs but they are possibly exposing your pet to other health risks. Before experimenting with any herbal or homeopathic treatment please be sure to consult a holistic veterinarian.

Know the current health of your pet – Test your dog!

The first step is get your dog tested for heartworm infection. NEVER give your dog any form of heartworm prevention (Rx or natural) before you get this test. Treating you dog with heartworm prevention medication while your dogs is infected. Your veterinarian typically will do a SNAP test which is a blood work screen testing for signs of diseases such as heartworm and Lyme disease. This is a convenient test because it requires only a small amount of blood and can be done in minutes.

Confirm the diagnosis before deciding on any form of treatment.

Heartworm Cures for your Dog

So really how dangerous is the heartworm disease to your dog? Well, in a word, it can be….fatal.

True story—We adopted a rescue dog who was carrying the disease when we welcomed her into our home. We did not find out she was infected until 4 months later.  That’s when symptoms of the advanced stages showed up. Her subsequent treatments really took a toll on her system….resulting in her being permanently damaged from the disease and treatment.

Basically, once a dog is diagnosed with adult parasites in the heart…. they must undergo (Immiticide) injections (starting with lots of prep work) to kill the adult worms. This is not medicine- this is a pesticide that poisons the adult worms.

This deadly treatment is a dangerous chemical that your dog is exposed to…because of this there can be serious side effects…. and permanent health implications. Think of it as a form of chemotherapy.

After treatment, this will be a dangerous period for your dog. The drugs injected into your pet will destroy the parasites…. and break them up. Serious infections can also be a health risk.

Depending on the severity of your dog’s condition your vet may also prescribe antibiotics as part of the treatment.

After Treatment- What Next?

A recovery period of restricted movement for your pet is required…because you want to keep the dead worms from getting back into your dogs blood system. This means lots of crate time if your dog is an active pet- up to a month or two.

Eventually these “worms chunks” are absorbed into your dog’s body.

This absorption period can take weeks or months…. and your pet is at severe risk of additional health problems such as seizure, shock, diarrhea, and vomiting.

It’s important your pet is kept calm with complete rest immediately follow this treatment (your vet will advise on a proper recuperative period).

Long term health effects from the adult worm damage to your dogs heart and lungs as well as the poisonous treatment can leave your dog with chronic health challenges.

So, is it worth it to have heartworm prevention medicine? My answer is…YES…heartworm prevention costs around $5-$15 a month and the cost to treat a dog with heartworms will cost between $400 and $1,200 (plus the health cost to your pet and the stress and emotional capital for you).

Heartworm Risk for your Dog

Don’t be a bad bug breeder!

Preventive care against this disease begins with reducing the exposure risks to your dog. This parasite needs the mosquito to spread and thrive. So mosquito control is one of the most important things you can do to break this cycle.

Even with strict heartworm preventative medicine treatment for your dog – you still need to do everything you can to limit her exposure to this disease.

The #1 FREE thing you can do for your dog in regard to Heartworm Prevention is to limit your pet’s exposure to mosquitoes.

What is your mosquito season?  How this disease can be transmitted depends on your climate…. your mosquito season.

The parasite life cycle cannot be completed unless temperatures are at 57 degrees for at least 45 days.   During this window – temps need to be above 80 degrees for at least two weeks.

So, if your climate hasn’t hit these marks then your pet is most likely safe without preventative medicine (at this time).

Most vets will recommend that your pet stays on monthly heartworm prevention year round…. but you can see this may not be needed.

So now you know the truth – and you can have that conversation with your vet.

Very few states would require year round prevention – deep south states including Texas and Florida probably are close to 12 month coverage.

Mosquito Protection for Your Dog

Limit peak mosquito hours – mosquitoes are most active during dusk and dawn hours. Avoid walking your dog during these high activity times. Never leave your dog outside for long periods during these times. NEVER use human mosquito spray on dogs.

Avoid having standing or stagnant water around your house – Mosquitoes need water to hatch and survive.  There are lots of places water can collect around your property.  Those area turn into mosquito breeding grounds.

Empty the bottoms of plant pots…. avoid anything that can collect water. Anything in your yard like a bottle cap….or a plastic bag can hold enough water to start a mosquito nursery. Grill and pool covers…water bowls…. and mud puddles are common collection points.

Limit the use of pesticides on your property– These poisons kill everything…. including the “good” insects you want around to eat mosquitoes. Dragonflies, spiders, and ants all eat mosquitoes.

DO use mosquito repellents for your dog – You can buy a reliable “dog safe” product or make your own all natural spray.

The Heartworm Bottom Line

Heartworm disease is serious business. Don’t ignore it…it’s a real threat to your dog. Let’s recap:

  • Get your pet tested. SNAP test as a screening test
  • Discuss heartworm prevention options with your vet
  • Discuss your mosquito season and the number of months that are a REAL threat of exposure
  • Get rid of mosquito hatcheries around your house
  • Take preventive measures on mosquito exposure with avoiding high mosquito times and using pet mosquito repellent
  • Seek a second opinion when exploring holistic treatments

Time to BUG Out!

Quick reminder—the content of this website is not meant to replace veterinary advice.

Please consult with your pets veterinarian before administering any form of treatment (prescription or natural) to your dog. So if you would like to explore holistic or homeopathic treatment options, and your current vet does not make those types of recommendations, you can find a vet at the American Holisitic Veterinary Medical Association. Do not experiment with your dog.

If you have any questions please feel free to leave me a comment below.

Best of luck in your dogs continued good health.


29 Comments on “Heartworm Symptoms – Canine Heartworm Medicine and Prevention For Your Dog”

  1. Dear Tim,

    Wow, thanks a lot for the in-depth information on Heartworm Medicine for Dogs. To be honest this is the first time I came across this information.

    You not only provided the causes but you provided with the solution as well. I got new insights and a lot of valuable information from your post.

    Thanks again for the great post on Heartworm Medicine for Dogs.

    Your Friend,

    1. Hey Paul,

      So happy to hear this article struck a chord with you.  There certainly is a lot of misinformation in the pet care world (much like other industries), so when all of us can share experiences, info, and ideas it helps all pet parents find better ways to keep our companions healthy.  Thank you again for visiting and hope to see you here in the future!  Cheers!

  2. Thanks for writing this great article on heartworm medicine for dogs.
    I did not know that full blown heartworm disease can result in 300 worms in the dogs heart. With an infestation like that even simple things like going for a walk would be really hard to do.
    thank you for the distinction that heart worm tablets kill bugs IF they exist, they do not form a barrier to stop them infecting your beloved “fur baby”.
    you said that mosquitos are the main cause and they need temperatures that are warm to hot in order to breed successfully. So I was just wondering if you think my dog could skip taking the heartworm tablets over the winter months?

    1. Hey Glenys- Thanks for visiting and glad that the info here was helpful.

      Heartworms are nasty parasites and they are toughest on dogs.  In my research I found that all animals (and people) can get exposed to the larvae in their blood but they never develop to adult worm stages in humans.  That’s scary!

      I would have a conversation with your vet regarding which months you may be able to skip your heartworm prevention..  I would NOT pay an office visit fee. I would call and set up a time when you can have a 3 minute call with one of the vets. 

      Personally,  we skip prevention tabs 4-5 months (depending on weather trends here in Virginia) for our dogs.  Many people skip treatment in winter months- but a vet will never recommend it first. I do think it is crucial to get the heartworm test every year though.

      Many vets don’t want to you take a break in treatment because it’s easy to forget to start again; leaving your dog exposed.  Others are like some medical professionals for humans that always believe that MORE is better.

      Heartworm prevention meds aren’t expensive so that is not the issue.  I don’t see the point in needlessly over medicating your dog.  These are toxic chemicals- that’s why they kill the parasites.  But what else do they destroy? 

       I have many pet parent friends who just treat their dogs once every three months because these drugs are so powerful.   So it comes down to your comfort level, climate, and the overall health of your dog of taking breaks in 

      For the record, I question every drug a vet recommends because unlike doctors for humans, veterinarian are allowed to SELL the drug they prescribe.

      Always smart to add a supplement like SPARK to help keep them well-balanced.

  3. Wow what an in-depth article. My doggy is a Labradoodle and has taken a liking to eating cat poop lol, we have to scan the garden before we let her out. I know there are many ways to contract heart worms, but would this make her more prone? We much prefer natural over prescription, and we always use preventive rather than wait for and illness to suddenly appear.

    1. Hi Sharon,

      Thanks for checking out this article.  Sounds like your Labradoodle has a nasty little habit.  As repulsive as it is to us- it’s perfectly normal to them.  Eating poop, known as coprophagia, is a common favorite pastime for dogs.  Kitty poop is a special treat due to a cats primary diet – typically high in protein and fat. It’s a very hard habit to break.

      The good news for her is that she can’t get heartworms from eating feces.  Heartworms can only be transmitted from mosquito bites since the larvae enter via bloodstream and not through the digestive process.

      Unfortunately your pooch is at risk of getting infrcted by other parasites that can pass from animal to animal with eggs in the poop.  Hookworm, tapeworm, and roundworm can all get passed to her if she eats inverted waste.  These can be passed to people as well – so don’t allow face licking. Eggs can be transmitted in their saliva.

      You may wish to try using a tasty dog toy that keeps her mildly distracted while she’s in the garden. I use a Kong toy filled with peanut butter that keeps my Lab occupied while she’s outside.

      Your smart to use heart worm prevention.  I like natural remedies as well but heartworms is something I don’t play around with. I take them off meds in winter months (non mosquito season).



      1. Tim, one thing eating poop is that it is a base supplier of vitamin B12. Passing through the first digestive system makes it more accessible to dogs.

        1. Hi Helen,
          Thanks for the sharing the B12 info. Animals are so in tune with their bodies…they seek out what they need. As you know, feces eating is quite common in the wild. So when dogs do it…it’s not totally surprising- yet still quite off-putting. 🙂 Dogs eat poop for various reasons. Some are behavioral issues…but like you said…often they do it due to a mineral or vitamin deficiency in their diet. I use this supplement to keep my guys on track…it’s called SPARK.

  4. Hey there Tim, heartworms are very prevalent in Australia. Especially in the northern regions. All dog owners I know, dose all year.

    Down where I live, in the very far south, the potential is there but it is much colder so we don’t hear about heartworm too much.

    No dogs for me but cats. Generally heartworms aren’t detrimental for cats.

    As for prevention, although we have an adjacent farm dam we also have a humongous amount of tadpoles. Our dam is pretty natural so all the frogs congregate there in egg laying season.

    Fortunately this co-responds to mosquito larvae season. And tadpoles just love to eat these little wrigglers.

    So with the cold and tadpoles I haven’t even heard of heartworm around our area.

    This is a great post to let people know of this danger. And it is amazing how many pet owners have a limited knowledge of pet problems. So well done for such an informative post.


    1. Hey Helen,
      Thank you so much for the awesome feedback. Sounds like you are in a nice low impact zone for mosquitoes. Those tadpoles and frogs are spectacular neutralizers of larvae. It’s true that nature can balance things most of the time…but I’m sure you have your share of natural things to deal with in Australia.

      I suppose in your area you don’t have to deal with can toads though…do you?

      Great to see you here and thanks again for sharing your experience. All the best! Tim

  5. Gosh, you hear about heartworm, but wow, is that what it is, how horrible! Often we are just ready to treat heartworm – rather than the prevention. And your advice and information on the prevention, is a much nicer option. A great article, it really outlines the devastating effects of heartworm, that perhaps many people, including myself were not aware of.  Thank you for your informative article!

    1. Prevention is the #1 thing we all need to consider.  Treatment is far too dangerous and toxic to guarantee a pleasant outcome.  Many dogs never fully recover from the treatments.  There is a “fast kill” option and a “slow kill” option…the slow kill can take up to 18 months.  It’s just a brutal treatment as you are basically cooking your dog with chemicals.

  6. I totally agree that heart worm is an awful condition and you raise a ton of great points in this article.  However, I’m not one to go for natural meds For such an invasive  condition.  I haven’t seen any hard and conclusive data that shows natural will work.

    We don’t live in a high risk area.  Mosquitos are limited, and heart worm rare, however we do give our dogs the treatment during the season.

    More  people should be aware of this heart worm and I as a gig lover am glad you wrote this.

    1. You are correct Stew- with this type of parasite once it’s in the organs you aren’t dealing with any old condition.  If someone wants to go with an all natural treatment approach they should consult a holistic veterinarian who can work with them on alternative treatment options.

      The key is prevention….because the conventional treatment for them is so toxic and dangerous.

  7. Thanks again for such informative suggestions regarding mosquitos and the connection with heartworms. My mother recently took in a stray dog and we have been noticing it’s lethargy and loss of appetite lately and thought that after administering internal stomach parasite pills and external parasite oil that we would see improvements. No such luck yet. After reading this we will go ahead and do the SNAP test and see if it’s heartworms.

    1. Sorry to hear of the news on your dog….strays and rescue dogs are more susceptible to this disease due to the amount of time they are exposed to the elements.  

      You are correct in that internal worms can be usually be handled with treatment by the pet owners…but heartworms are a different story because they live and develop in the small vessels of the bloodstream as opposed to the digestive system like other worms.  Your vet can get to the bottom of this…i wish you the best of luck.

  8. Thanks Tim, you’ve managed to really get me concerned with this heartworm problem in dogs. This is something I never have been informed of. Where I live the mosquito’s are huge and very nasty. I just got my wife a her first ever puppy and would break her heart if a horrible parasite like this infected her new best friend:)

    I’m really glad I found your work here, I took the puppy to the vet for a check up the other day and was looking over the readily available info there, and found nothing like this. Forever Thankful Rob.

    1. So happy to hear about you new family member.  Puppies are such fun…so full of energy and life.   As long as they are healthy they can fight off a lot of things naturally.  Prevention against heartworms is essential.  There is no need to over-medicate them…and as long as you know your mosquito season you can work with your vet to keep him protected-wishing you all a long happy life to together!

  9. Hi and thanks for the tips here in this article as I think it’s so important to know just how your dog can be in danger when your not expecting it. I hope that many dog owners will definitely try your preventative measures before their dogs get this. As you point out other than the expense, it is so harmful to treat them with natural or medicinal remedies. Thanks Kenny 

  10. I highly agree with your statement that prevention is the best defense! We’ve had a few dogs over the years and in the beginning we were not always paying enough attention to this, until one of the dogs started showing symptoms. We weren’t informed well enough so when we got the news from the vet about the treatment plan we were shocked!

    Thanks for putting out the word on this and I hope lots of dog owners will read this!

    p.s. Our dog survived, but it was a long and costly process…

    1. I too had to go through heartworm treatments with a dog we rescued…poor thing was already exposed by the time we got her.  The physical toll it takes on the dog is brutal.  

      I know a few people who do not use heartworm medication as prevention because they are so toxic.  It’s a personal choice for sure.  One slip up though and it’s pretty grim.  If you are in an area with a long mosquito season its just not worth the risk.  

  11. I have been taking care of my girlfriend dog for a while now. Learning everything I can on the internet while enjoy my time with this cute creature. This is the first time I’ve heard of heart worm. Sounds really scary!

    After checking the list of symptoms, my girlfriend’s dog is safe. What a relief. I’ll keep the list in mind and maybe bookmark this page so that I can come back if necessary.

    Thanks a lot for sharing this very educational post.

  12. Oh, that’s really an awful thing for a dog to have.  So, spraying them with bug repellant is okay?  I never would have thought of that.  Our dogs have the really thick fur, but we trim their fur in the summer.  That’s really good to know so we can take care of them better!  Thank you so much for this advice 🙂

    1. With Heartworms you are only worrying about mosquitoes…so if you can peak mosquito hours and protect them with repellent while yo have them out you are going a long way to protect them.

      You must use a repellent safe for pets…no not use products made for humans.  Sprays people use contain DEET and this is toxic if ingested…..dogs lick…so its a stay away.  Get a natural repellent made for dogs like this one…or you can make a homemade batch of dog friendly mosquito repellent yourself if you want to try something fun.

  13. Heartworm medicine for dogs is a very informative article. 

    With this information people can protect there dog from the nasty mosquitoes. I never how dog got those nasty heartworms. 

    Now that i know how to prevent them I  will be get you suggested product. I really like this article It was so informative to me by giving me ways to keep my pets  safe.

     Thank you for this great article I really appreciate all the information.

  14. I really did not know how this can be that dangerous and in some cases fatal. I live in that place where mosquito are very spread and my dog is often outside and I did not pay attention on this disease. Thank you a lot for warning us and I will protect my dog as soon as possible.

  15. Wow this must be scary disease for dogs and dog owners. It can devestate dogs lives for months if they are lucky enough to be treated for it.

    Thankfully I live in a mosquito free area so this is something I wasn’t aware of but this message definitely needs to be spread amongst dog owners where these parasites are a problem.

    This is a horrible infection that is best treated with prevention.

    A very interesting article

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