what you always wanted to know – In the Name of the Dog

ce que vous avez toujours voulu savoir – Au Nom du Chien


Maybe you just received a postcard or email from your veterinary clinic saying that heartworm season is approaching and it’s time to act before you put your dog at risk for this unwanted parasite. Distraught, you then make an appointment at the clinic to perform a test and then leave relieved with the medication to give your dog for the season. But have you ever wondered what are your dog’s chances of contracting this parasite and more importantly how does this medication work to prevent heartworms?

In our dog’s life (as in ours), we often act out of habit, because everyone does it and without asking questions…because it’s the norm. This is why today I will try to make you better understand a subject on which we are quick to give medication…but without ever really knowing the cause, other than what the veterinarian tells us.

Heartworms are spread by mosquitoes.

Treatments for heartworms are spread by fear.

The first thing to know is that the product that is being sold to you as a preventive treatment …is not one in the sense that it does not prevent the transmission of the parasite . Your dog will therefore still be bitten by the mosquito and infected. The medication you give your dog (which is actually categorized as pesticides ) is therefore a treatment… period, whether your dog is infected or not. To draw a parallel, would you find it logical to take a morphine pill every morning…in case you were in severe pain during the day? Yet this is what you do to your dog…you treat him even before you have confirmation that he is affected.

But let’s talk about it:

What does it take for a dog to become infected with the heartworm parasite?

A long series of very specific steps must be followed if a dog is to be infected with heartworm.

  1. To infect a dog…it first takes mosquitoes (so a hot temperature and/or pools of stagnant water). Specifically, you need a female mosquito that is the right species (because not all kinds of mosquitoes can carry the parasite). The female mosquito therefore serves as an incubator for the reproduction of baby heartworms, called microfilariae. If your dog is bitten by a male mosquito…impossible for him to get infected! In addition, it is impossible for your dog to be infected by any animal other than a mosquito.
  2. The female mosquito that will bite your dog must first have bitten a dog infected with sexually mature male AND female heartworms that will have produced microfilariae.
  3. Baby heartworms (microfilariae) absolutely must  be at the L1 stage of development by the time the mosquito bites the dog to draw blood from it. In all, there are 5 stages of development: L1 to L5.
  4. 10 to 14 days later, if the temperature is ideal *, the microfilariae will grow inside the mosquito to stage L3, the first infectious (dangerous) stage.
  5. Madam mosquito will then have to bite your dog while the parasite will be at stage L3 (not before). Then, if all the conditions are met, the parasite grows just under the skin of the dog for 3 to 4 months, until stage L5. It is only after this period that the parasite will enter your dog’s bloodstream. But even at this point, the fight is far from over.
  6. Only if your dog does not have a strong enough immune system will the worms develop into the adult stage.
  7. It takes about 6 months for the larvae to develop into the adult stage. If adult males and females are present then they will be able to produce babies (inside your dog). However, these babies will die unless a stage L3 mosquito intervenes. Otherwise, adult worms will live for several years before dying naturally .

In summary: a female mosquito of a particular species must bite an infected dog with heartworm babies at the L1 stage, must keep those babies until the L3 stage, and THEN it must bite your dog at that exact moment. Adult worms and their babies will eventually die unless bitten again!

Ah, and most importantly: All of this has to happen while it’s 14 degrees Celsius and above, day AND night . If during all these steps the temperature drops below 14 degrees Celsius for just one night…the whole process has to be repeated!

As you can see, the stars really have to be aligned for your dog to have a chance of getting infected. That said, I’m not saying infection is impossible. What I’m saying is that it’s a hell of a lot harder to get than the veterinary community would have us believe. But after all, are they there to objectively inform you or sell you products ? Probably a little of both, but in what proportion? I would bet (in a purely subjective and in no way factual way) on 70% selling the product and 30% informing you. If it wasn’t, I wouldn’t have just taught you about the transmission cycle of heartworms, your vet would have!

Is “preventive” medication safe? 

No medication is completely risk-free and there are obviously no long-term studies on the dangers of antiparasitic medication. Such a study would be very long and let’s face it, the pharmaceutical companies have no interest in updating any risks associated with their products. Knowing that, who would want to fund a long-term study?

I invite you to look at the packaging of your product. There you will see warnings such as:

  • Call a physician immediately if swallowed
  • Keep out of reach of children
  • Wash your hands immediately after use

How can this type of medication be safe for your dog but so dangerous for us that we absolutely have to wash our hands after touching it? If I don’t dare put it on my skin, why would I put it on my dog’s?

In fact, this type of medication has two main effects on the dog’s body:

  1. Weakened immune system
  2. Forces the organs (kidneys and liver) to work harder to remove toxins from his blood

The side effects:

Ideally, your veterinarian should have warned you of the risk of side effects following the use of the product he recommends. Otherwise, the packaging certainly contains the product monograph which I strongly advise you to read. You should also know that the majority of products have received a study of only 2 weeks in order to list the side effects. With 2 weeks of studies carried out by the pharmaceutical companies, we unfortunately completely miss the long-term effects.

In addition, I have also released for you the number of cases of side effects  reported  to the FDA (US Food and Drug Administration). The important word here is “ reported ” since as you can imagine, the majority of cases are not. After all, it takes time to report the problem to the manufacturer and the veterinarian does not get anything out of it and that’s IF the link is made between the symptoms and the taking of this medication.

Here are the three main products sold in Quebec and their side effects, followed by the number of cases reported to the FDA.

  • Revolution ( salamectin ): inefficacy (the dog under treatment was infected the same) (5902), vomiting (1788), depression/lethargy (1759), diarrhea (1056), anorexia (1015), convulsions (642), tremor (442 ), ataxia (355) and death (236) .
  • Advantage Multi ( imidacloprid ): depression/lethargy (366), vomiting (313), anorexia (155), hyperactivity (144), diarrhea (126), inefficacy (112), tremor (106), ataxia (93) and anaphylaxis ( 80).
  • Heartguard ( ivermectin ): ineffective (15,161), vomiting (2,457), diarrhea (1,366), depression/lethargy (1,309), anorexia (701), seizures (586), ataxia (315), and death (264) .

Additionally, according to the American Veterinary Medical Association, 48% of deaths from drug interactions are due to antiparasitic treatments . Also, 65% of all drug reactions are related to the same products.

Now, I’m not telling you to stop treating your dogs. What I am saying, however, is to think before proceeding with your eyes closed, now that you are better informed about:

  1. The conditions necessary for an infection to take place.
  2. Side effects of different products.

How to successfully stop using these drugs while protecting our dog?

As I told you earlier, medication does not prevent heartworms. What the medication does is kill the larvae (if) present in your dog before they develop into an adult.

IMPORTANT: It is very dangerous to use this type of medication if your dog is a carrier of ADULT heartworms. It is for this reason that your veterinarian performs a test before any treatment begins. He wants to make sure your dog doesn’t have adult worms, otherwise another type of treatment would be needed.

The secret to getting rid of this type of medication: test more often!

We have learned that medication should be used to kill baby larvae (microfilariae) but never to treat adult worms. We also learned that it takes at least 5 months for baby larvae to develop into adults. Knowing this, then why give medication every month when it would suffice to carry out tests at the right time? By carrying out a test every 4 months…no larva will ever make it to the adult stage! This option not only removes chemicals from your dog’s body but also saves you money.

The medication will cost around $150 per year, depending on the product used and the size of your dog. Knowing that a test is around $30, even if you do 4 per year (which is way too much in Quebec since we don’t have mosquitoes all year round), you are still cheaper than with the medication! It is therefore a less expensive option but above all, better for your dog’s health!

One more reason to stop the medication?

Heartworms are becoming increasingly resistant to medication. Every year, more and more dogs get infected DESPITE being on medication . It happened to 15,161 dogs on Heartguard, 5902 dogs on Revolution and 112 dogs on Advantage Multi. And again, it’s only the number of reported cases…

Ironically, the American Heartworm Society responds by saying that more medication is needed! It is not really surprising to hear this answer when looking at which companies sponsor this association:

Bayer, Elanco, Merial, Virbac, Zoetis, Ceva and Merck are all pharmaceutical companies working in the animal field! Let’s say we can say that they preach for their parish.

Today, 50% of dogs die of cancer. Don’t you think that kind of chemicals have something to do with it?

I believe it is our duty to our dog to question why the vet wants us to give this product. If we’re trying to make you feel bad, here’s my list of reasons that might help you:

  1. The worms are becoming resistant to the medication and more and more treated dogs are getting infected anyway.
  2. Medications contain many toxic ingredients (think about handling rules)
  3. Tests exist to know if the dog has worms or not
  4. Testing is less expensive than treating (although cost is not a reason personally…but my dog’s health is)!

Are there natural alternatives to medication?

The first thing to do would be to control the mosquitoes . No mosquitoes, no heartworms! Do your best to avoid stagnant water sources that are conducive to mosquito breeding.

Then, I opt for a natural (raw) diet for my dog. A dog that eats raw is less interesting for mosquitoes, its blood not being full of sugar like a dog that eats kibble (where 40-60% of the kibble is made of carbohydrates which are transformed into sugars by dog’s body). In the wild, coyotes, foxes and wolves have been identified to have strong resistance to heartworm infections. Why? They eat food that is biologically appropriate to their species. Since the dog is a carnivore, the most biologically appropriate food is (raw) meat! Think about it: if you go to the zoo, watch what the tigers, lions and other carnivores eat. Fresh meat…not kibble!

In addition, I do everything in my power to ensure that my dog ​​has a  strong immune system.  This means reducing vaccination to only what is necessary and avoiding (pharmaceutical) chemicals as much as possible, especially antibiotics when they are optional.

Another way to improve your dog’s immune system is to incorporate fresh ingredients such as:

  • apple cider vinegar
  • pre and probiotics
  • tripe verte
  • a good source of Omega-3 fatty acids
  • coconut oil
  • Garlic
  • curcuma

To conclude, the purpose of this article is to allow you to better understand the reproductive cycle of heartworms (and the multitude of factors necessary for its transmission) as well as the possible side effects of associated drugs, which we explain to you too often mistaken as a “preventive” treatment.

The health of our dogs is important to us all and I hope this reading will help you make more informed choices for your dog, whether or not you choose to continue this type of medication.

On his behalf, thank you!


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