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Heartworm is a scary word for all pet owners. Every vet clinic displays terrible photos of hearts effected by heartworm and if you don’t want your dog to end up with those long ugly worms, you’d better give them monthly preventive heartworm drugs, preferably year round.


Vets are afraid of heartworm because they know how difficult and harmful heartworm treatment can be. So they want to scare us into buying preventive drugs. Even holistically-minded dog owners who feed raw, minimize vaccines and try to avoid toxic chemicals for their dogs, don’t always take the scary leap of faith to stop giving heartworm medication.

Conflict of Interest

Apparently it is the big pharmaceutical companies that make the heartworm drugs that sponsor the very production of the terrifying information about heartworm disease. They provide downloadable brochures, maps, infographics and even children’s games to teach dog owners about the risks of heartworm disease. There are all kinds of resources that vets can use to improve “compliance.”

It’s all designed to get you to use heartworm medication for your dog. There are strict guidelines for diagnosis, prevention and management of heartworm disease. Right now, wherever you live, they recommend giving your dog heartworm drugs every month, year round, to protect them.

It seems to me that this is a conflict of interest? Certainly these companies have a vested interest in giving you as much information as possible to convince you to buy their drugs for your pet.

Heartworm “Preventives” Are Not Preventive

Heartworm preventive drugs don’t prevent your dog from being infected with heartworms. Instead, they work by killing heartworm larvae that may already be in your dog’s body. So they’re actually treatment drugs, not preventives. If your dog hasn’t been infected, you’re treating them for something they don't even have.

When you give your dog monthly heartworm “preventives,” what you’re really doing is poisoning the heartworm larvae before they grow into adult heartworms.

Heartworm Drugs Are Neurotoxic

Heartworm drugs are pesticides. Just the idea of putting pesticides into your dog should make you hesitate. The drugs are neurotoxins … and the way they work is by paralyzing the parasites’ nervous systems.

Side effects reported in dogs are conditions that involve the nervous system … things like:

  • convulsions

  • ataxia (staggering/incoordination)

  • trembling

  • the list is long....

Are Heartworm Drugs Really safe For Your Scottie?

The warning labels on heartworm medications are very clear: if you or your child should accidentally ingest the drugs, you’d better rush to the doctor immediately.

Does this make sense to you? According to the manufacturer and your vet, it’s “safe” for your dog to take this drug every single month, year round, but not for you – even once. The actual list of common side effects in dogs is long and includes death!

So, are heartworm meds safe for your Scottie? I’d say NO.

It’s Not So Easy For Your Scottie To Get Heartworm

In all the studies involving Heartworm and Heartworm drugs there is no breed specific information. I have worked with many breeds of dog over the years and I know that short haired breeds seem to be much more susceptible to mosquito bites. Scotties are a double coated breed and because of this it is very difficult to imagine that mosquitoes would even be able to bite a Scottie on 90% of their body area. Out of all recorded cases of Heartworm how many Scotties have been effected?

I don't know about your Scotties but mine spend much of the warmer months inside with the air conditioning anyway.

Heartworm disease is transmitted by a mosquito bite. But it’s not even that simple. For any dog to get infected, here’s what has to happen:

  • Heartworm is spread only by certain breeds of mosquitoes (not all breeds can transmit heartworm)

  • To be a heartworm carrier, the mosquito must have bitten an infected dog or other infected animal

  • Dogs can’t catch heartworm from other infected dogs – it can only come from an infected mosquito

  • The weather must be warm enough for heartworm larvae to develop in the mosquito

  • The dog (or other host where the mosquito picks up the heartworm) must already be infected with mature male and female heartworms and they must have produced microfilariae that are alive when the dog is bitten and are at the site of the bite

  • If a dog is bitten by the pregnant female mosquito, her microfilariae are released into the circulatory system and they must then wait there for a new mosquito to bite the dog again.This is the only way microfilariae can begin to develop into adult heartworms … they must be picked up by a second mosquito to develop into larger, and more mature larvae. They do this while they’re in the mosquito’s body and this can take a few weeks to occur. If the temperature falls below 14 degrees, they’ll die off.

Summary: it’s not just being bitten by a mosquito that can give your dog heartworms. It has to be the right kind of mosquito – it has to be a female mosquito -- it has to be a mosquito that has bitten another animal that was carrying microfilariae, and then bites your dog … and the temperature has to be warm enough throughout the entire biting, incubating, carrying and rebiting cycle.

Heartworm Risk Is NOT Everywhere

Heartworm preventative drugs are recommended year-round for dogs, no matter where you live. The rationale for this is that there have been cases of heartworm all over the place.

But is this actually true? Is that really enough risk to justify giving your Scottie a poisonous pesticide every month – one that could cause them to become seriously ill or even die?

Not to mention that Heartworm Drugs Are Becoming Less Effective

It’s known that heartworms are becoming resistant to heartworm drugs.


It’s true. Wild canines like wolves, coyotes and foxes don’t seem to get sick or die from heartworm disease. These wild animals are outdoors 24/7, so they’re exposed to a much higher risk of being bitten by mosquitoes than our domestic dogs who spend much of their time indoors. So why are our dogs more susceptible to heartworm disease? (again I would argue that it might have something to do with their thick protective coats that protect them from mosquito bites).

One of the keys is the immune system. The difference lies in what we do to our domestic dogs to weaken their immune systems compared to wild canines… things like:

  • Vaccination or over-vaccination

  • Poor nutrition

  • Exposure to toxins like drugs, pesticides, fertilizers, household cleaners, and other chemicals

So if your dog has a strong and healthy immune system they are naturally well equiped to kill any microfilariae and prevent them from reproducing.

What I Do For My Scotties…

You might think your Scottie's immune system is only capable of dealing with viruses, but they can defend themselves against heartworms and microfilariae. Special white blood cells can seek out and destroy heartworms and their larvae. Again, the immune system is the key to helping your Scottie prevent heartworm. Here are some things I do to help strengthen my Scottie's immune system:

  • I feed a fresh, balanced bone and raw food diet

  • I keep vaccines to an absolute minimum

  • I avoid prescription drugs like antibiotics or non-steroidal anti-inflammatories

  • I avoid chemical pest control products, including spot-on products, dewormers and heartworm medications!

  • I don’t use pesticides or herbicides on my lawns

  • I use natural cleaning products in my home

I feed my Scotties a little garlic which helps to make them less appealing to insects. Garlic is safe for dogs in moderation. You can safely give up to 1/2 clove of garlic to your adult Scottie (use regular sized garlic, not jumbo). Do not give garlic to puppies under 6 mths of age and puppies 6 to 12mths only 1/4 of a regular sized clove per day.

Peel and chop the garlic about 15 minutes before feeding, then add it to their food. Start feeding garlic one month before the start of mosquito season. When using garlic only as a flea and tick repellent, it is recommended to feed each day for two weeks, then twice a week for maintenance. If bathing is required during mosquito season repeat two weeks of daily garlic etc...

There are also natural topical repellent ideas to use on your dogs if you live in particularly high risk areas. e.g. lots of mozies or high numbers of reported cases of Heartworm. Google NEEM oil or Lavender essential oil! Or check out my next blogs as I am currently researching natural repellents and natural food additives designed to support and protect my Scotties.

REMEMBER - All of these measures act to reduce environmental challenges to any dog's immune system. Armed with a strong immune system our Scotties are ready to repel and eliminate all worms and other parasites. I strongly believe that Scotties are a robust breed with a protective coat. I think it is much better to focus on keeping our Scotties in tip top shape rather than exposing them to unnecessary pesticides and toxins in the name of "protection", when they already have it!

Check out for more Scottie info and tales.

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