Why I Don’t Give My Dogs Heartworm Medicine (And Why You Shouldn’t Either)

Heartworm In Dogs

Some vets tell dog owners that heartworm medicine is too dangerous to use.

Does that surprise you?

Holistic veterinarian Glen Dupree didn’t want his patients taking heartworm medicine. Dr Dupree found that a strong immune system was enough to protect his dogs from heartworm. And he also knew that giving dogs neurotoxic drugs every month would harm that immune system.

“I assume my dogs have heartworms,” said Dr Dupree. “But there’s a big difference between heartworms and heartworm disease.” 

And that difference is a fully functioning immune system.

There are many holistic vets who don’t recommend using heartworm medicine. But the pro-health approach to parasite prevention isn’t all that popular … yet.

Here’s why holistic vets avoid heartworm medicine for dogs …

Your Dog’s Immune Systems Fights Parasites

When you think of the immune system, you probably think about diseases like parvo or kennel cough … or cancer.

But your dog’s immune system also protects his body from parasites … like heartworms.

A well-tuned immune system is the difference between a few heartworms … and a large heartworm load that affects your dog’s health. That’s what Dr Dupree was talking about. 

So a big part of protecting your dog from heartworm is protecting his immune system. 

What Causes A Weak Immune System In Dogs

Over-vaccination is a big problem. While vaccines can protect your dog from infectious disease, they come at a cost. One key reason for this is the ingredients in vaccines. 

Toxic Vaccine Ingredients

Here are just a few of the toxins in vaccines …

  • Mercury, which is neurotoxic and causes cancer and autoimmune disease.
  • Aluminum, another neurotoxin. It can cause degeneration of the brain and nervous system. It’s especially harmful in young dogs. And it increases the toxicity of mercury. So the “safe” levels of mercury in your dog’s vaccines are severely underestimated.
  • MSG, a common food flavoring that’s a neutotransmitter affecting your dog’s brain response. 
  • Formaldehyde, one of the most hazardous and highly cancer-causing compounds known.

So a dog who’s been vaccinated regularly with these toxic ingredients will have a hard time being truly healthy. 

RELATED: Learn more about toxic ingredients in your dog’s vaccines …

Vaccines Suppress The Immune System

As well as having harmful ingredients, vaccines suppress the immune system.

Immunologist HH Fudenberg says if your dog receives just one monovalent vaccine, his cell-mediated immunity will be cut in half. And just two vaccines will lower it by 70%.

Monovalent means the vaccine has a single virus. But most dogs get several at the same time. Here’s what HH Fudenberg says about 3-in-1 vaccines:

“… all triple vaccines markedly impair cell-mediated immunity, which predisposes to recurrent viral infections, especially otitis media, as well as yeast and fungi infections.”

RELATED: Immunity without the needle … 

Yet most dogs get 3 to 7 vaccine components at a time. They get too many vaccines … and much too often. It’s no wonder vets worry about heartworm. 

But that brings me to …

The Side Effects Of Heartworm Meds

Just as vaccines can damage the immune system, so can your dog’s heartworm meds. 

Heartworm meds are neurotoxins. They kill larvae is by paralyzing them. So it’s no wonder that they can also damage your dog. In the side effects below, you’ll see neurological problems … like ataxia, tremors, convulsions, or seizures

And that’s just in the short term. Nobody really knows the long-term risks of heartworm meds. Because they haven’t tested the effects of giving them … for several months every year, for your dog’s whole life.

So the best guess we have is the adverse reactions that occur right after taking heartworm meds. 

Short Term Reactions To Heartworm Meds

Here are some reported side effects of common heartworm medications for dogs …

HEARTGARD And TriHeartPlus (ivermectin)

Depression/lethargy, vomiting, anorexia, diarrhea, mydriasis, ataxia staggering, convulsions and hypersalivation.

INTERCEPTOR (milbemycin oxime)

The above reactions plus weakness.

SENTINEL (milbemycin oxime)

Vomiting, depression/lethargy, pruritus, urticaria, diarrhea, anorexia, skin congestion, ataxia, convulsions, hypersalivation and weakness.

REVOLUTION® (selamectin), Topical Parasiticide For Dogs and Cats

Vomiting, loose stool or diarrhea with or without blood, anorexia, lethargy, salivation, tachypnea, and muscle tremors, pruritis, urticaria, erythema, ataxia, fever. There have been some reports of death and seizures in dogs.

ProHeart 6 and Proheart 12

These are injectable drugs that last for 6 or 12 months. Severe allergic reactions (anaphylaxis): facial swelling, itching, difficulty breathing, collapse; lethargy (sluggishness); not eating or losing interest in food; any change in activity level; seizures; vomiting and/or diarrhea (with and without blood); weight loss; pale gums, increased thirst or urination, weakness, bleeding, bruising; rare instances of death. 

The maker withdrew this drug from the market in 2004 because of deaths. But they’ve brought it back. And now they’ve introduced ProHeart 12 too! The really scary thing about these injectables is that if your dog has a reaction, you can’t just stop giving them. The drugs are in his body for 6 or 12 months. 

RELATED: FDA approves potentially deadly ProHeart 12 …

And of course, if your dog gets side effects from the meds, it’ll weaken his immune system too. And a weaker immune system makes him more susceptible to all diseases … including heartworms.

How Dogs Get Heartworms

Let’s get one thing straight. 

Heartworms are transmitted by mosquito bites. That’s the only way your dog can get them. He can’t catch heartworms from another dog … or even another animal. 

And there’s one other thing that needs clarifying. 

Microfilariae Vs Larvae

People often use these words interchangeably. And even vets seem confused. 

Microfilariae and larvae are both young heartworms. But they’re not the same. 

Microfilariae are heartworm babies. Larvae are the toddlers that grow up from those babies. They grow from microfilariae to larvae inside mosquitoes.

  • When adult heartworms breed inside an animal, they create microfilariae. 
  • When a mosquito bites an infected animal, it picks up the microfilariae. 
  • After the mosquito picks up the microfilariae, they grow into larvae in the mosquito

With the understanding of that difference, let’s talk about how mosquitoes give your dog heartworm. It’s quite a complicated sequence of events. 

  • The mosquito picks up heartworm microfilariae by biting a heartworm-infected animal. 
  • Microfilariae grow into larvae in the mosquito. 
  • The mosquito with heartworm larvae bites your dog, leaving larvae in him.
  • Over about 6-7 months, the larvae can grow into adult heartworms in your dog.
  • Eventually, the adult heartworms start breeding … creating microfilariae. 

If you’d like a visual aid to explain the process, the AHS has quite a good diagram

That’s a lot of background … but it’s important to grasp it so you know how to protect your dog from heartworm without toxic drugs. 

How To Prevent Heartworm Naturally

Yes, it’s possible to protect your dog without harmful drugs. Even in places where mosquitoes are bad. 

It might not be as simple as giving that tasty heartworm chew every month … but it’s a lot safer for your dog! 

Again, remember, the goal of heartworm meds is to kill the larvae before they grow up. But your dog’s own immune system can do that … without drugs. 

That’s the reason for focusing on the immune system … it’s the first step in avoiding heartworm disease. 

#1 Support Your Dog’s Immune System

Your healthy dog’s own immune system can prevent heartworm disease. Yes, that’s heartworm disease, not heartworms. They’re not the same thing, as Dr Dupree said. 

It means … your dog could have heartworms in his body. But they don’t have to make him sick. 

Think about wild dogs like wolves, coyotes or foxes. These animals are outdoors 24/7. So they’re much more likely to get mosquito bites than domestic dogs who live mainly indoors. Wild dogs might have heartworms … but research shows they don’t get heartworm disease. And they don’t die of heartworms. 

Wild dogs are healthier because they eat natural diets. And they’re not exposed to drugs and toxins like domestic dogs. 

And you can strengthen your domestic dog’s health with a natural lifestyle too. That means …

  • Feed a natural, raw meat-based, whole food diet (not kibble)
  • Minimize vaccines
  • Use natural remedies instead of pharmaceutical drugs
  • Use natural flea and tick prevention
  • Don’t use chemicals in your home and yard
  • Give your dog fresh spring or filtered water
  • Give him plenty of exercise

Even if you aren’t already doing these things, jt’s not too late to start. Your dog won’t develop a robust immune system overnight. It’ll take time … but you can help him along by giving some immune boosting herbs and supplements

RELATED: Immune system boosters that work …

The next step in preventing heartworm is …

#2 Avoid Mosquito Bites

If you live somewhere with a lot of mosquitoes, try to keep them away from your dog. 

  • Avoid standing water in your yard or on walks
  • Keep your dog indoors at dawn and dusk or when mosquitoes are most active
  • Avoid swampy mosquito breeding areas on walks
  • Use natural mosquito repellents to keep the bugs away
  • Feed fresh garlic to help repel mosquitoes

PRO TIP

Dr Patricia Jordan also suggests keeping chickens … as they love to eat mosquitoes!

Steps #1 and #2 will keep most healthy dogs heartworm free. But you may want a layer of extra protection, especially if you live in a high mosquito area … or your dog is new to the natural lifestyle!

#3 Use Herbal Heartworm Protection

There are different ways to do this. 

Buy A Ready-Made Herbal Blend

There are some pre-made herbal heartworm products you can buy. 

As you search, be aware their websites usually won’t directly say they prevent heartworms. That’s because the FDA won’t let manufacturers make that claim for natural products.  

So they have to be a bit subtle in the language they use to describe their product. They’ll say things like … 

  • Supports normal heart function
  • Promotes healthy blood circulation 
  • Helps detox foreign contaminates
  • For use during mosquito season

This means you might have to call the company to find out if their product really protects from heartworm. They’ll be more open on the phone. 

You may see ingredients like …

  • Hawthorn (a heart-strengthening herb that helps circulation)
  • Dandelion leaves (help with detox)
  • Garlic (anti-parasitic, immune support and insect repellent)
  • Neem (immune support, insect repellent)
  • Wormwood (antiparasitic)
  • Black Walnut (antiparasitic)
  • Black seed (antiparasitic

Use Individual Herbs

For this option it’s best to work with a holistic vet or herbalist. A professional can recommend a protocol to protect your dog from heartworm. The advantage of this approach is that it can be tailored to your dog’s individual needs. 

Your herbalist may recommend various combinations of herbs. They may include herbs like …

  • Wormwood (antiparasitic – use only with professional guidance)
  • Hawthorn (strengthens heart function)
  • Ginger (supports heart disease risk factors)
  • Thyme (supports immunity, repels mosquitoes)
  • Garlic (supports heart health, repels insects)
  • Peppermint (bug repellent)
  • Cinnamon (for heart and neurological health)
  • Cloves (antiparasitic)
  • Dan shen (supports cardiovascular health)
  • Medicinal mushrooms (boost immunity)
  • CoQ10 (heart-strengthening supplement)

You can find a holistic veterinarian who uses western herbs in their practice. Search at ahvma.org and select Western Herbs as the Modality.

Extra Herbal Support

Herbalists Greg Tilford and Mary Wulff recommend giving echinacea if you’re going into high risk areas. Echinacea supports your dog’s immune system. You can give most dogs 12-25 drops of tincture 3 times a day, for 3 days before and 3 days after your outing. 

Caution: Don’t use echinacea full time. Most experts say it’s best used when the immune system needs extra support. 

There’s one other thing you can do to protect your dog … even if you don’t give any drugs or herbal remedies.

#4 Test For Heartworm More Often

Most vets recommend testing for heartworm once a year, in spring. But if you test your dog for heartworm more often … you’ll find an infection sooner. And that means you can start treating him at an earlier stage.  

Keep reading … because there’s some detailed information you need to know. 

First, let’s get into the different types of heartworm tests. 

How Heartworm Tests Work

There are 3 different types of heartworm tests. 

Antigen Test

The regular test your vet does is an antigen test. Here are the shortcomings of this test. 

  • It can only identify adult female heartworms. That’s why your vet says it takes heartworms 6 months to show up on testing. 
  • Heartworm antigen can be in the blood within 5 months. But most dogs won’t show antigen until 7 months after infection.
  • These tests also may not pick up a low worm burden. If your dog only has one or two female worms, the test has a 30-40% false negative rate. 
  • Some dogs won’t show antibody at all due to “antigen-antibody complexes” in the blood. 

So that’s why your vet may also do a microfilariae test. 

Microfilariae Test

This test will show if there are microfilariae in your dog’s system. And official recommendations have changed. In the past, vets only did it if the antigen test was positive or weak-positive.  

The AHS now recommends doing the microfilariae test annually. This avoids false negatives on the antigen test. A positive microfilariae test confirms there are mature heartworms in your dog. And they’re breeding. 

Those two are the tests your vet likely knows about. But there’s a little known, third type of test.

DNA Heartworm Test

This is a DNA test using PCR (polymerase chain reaction) technology. It tests for heartworm DNA in your dog’s blood.

The place to get this test is HealthGene in Canada. The test is the D319 Canine Heartworm (Diofilaria immitis) test on this page.  HealthGene confirms that the test identifies heartworms at all stages. That means it shows microfilariae, larvae and adult heartworms.

You’ll need your vet’s help, because HealthGene won’t work with you directly. Your vet can order the test kits here. Then she’ll have to send the sample to HealthGene in Canada. 

So … which test should you get? And how often?

Which Heartworm Test Should You Choose?

If your vet will help you get the DNA test … the best choice is the DNA test by HealthGene. 

Again … when an infected mosquito infects your dog, it transmits larvae. The larvae take 6-7 months to grow into adults. The DNA test will identify larvae in your dog’s blood. 

Finding the larvae vs adult heartworms means the infection is much easier to treat. So you’d only need to give heartworm meds if your dog’s DNA test was positive for larvae. And not every single month. Or you could use a herbal remedy instead

It’s more hassle to get this test. But it’s doable … you just have to talk your vet into it! 

But if that’s too hard (or expensive) … or you just can’t find a vet to help you … 

Next best is the regular antigen test your vet does. But you’ll need to do it more often than once a year.

Vets insist there’s no point in testing more often than once a year. That’s because they know the test won’t be positive until 6 or 7 months after infection. So they test in spring, before prescribing heartworm meds for the next season. 

But wouldn’t it be better to know if your dog’s positive sooner rather than later? Your vet waits until several months after the end of mosquito season. But if peak mosquito season where you live is during summer months (June through August) … your dog could test positive as early as December or January. Why wait till spring to find out?

It could be worth a couple of extra tests starting 6 months after the beginning of mosquito season wherever you live. And then, if your dog is positive, you can start treating him a few months sooner … before more adults develop.

PRO TIP

The microfilariae test is just a way to confirm the accuracy of the antigen test. So if you want to be more confident, you could do it alongside the antigen test.

Heartworms Are Becoming Resistant To Meds

You might have heard that heartworms are becoming resistant to heartworm meds. The more we use the drugs, the less effective they become. In the US, more and more dogs each year are getting heartworm while on the meds.

Yet the AHS had an ironic response to these reports. Their solution is to recommend heartworm meds year-round. Let’s see … the heartworms are becoming resistant to the drugs … so the solution is to give more drugs? Does that make sense to you?

Why do they think giving heartworm meds more often is the answer? Well, it might have something to do with the companies who fund them …

Their sponsors are names like …

  • Merck
  • Virbac
  • Zoetis
  • Elanco
  • Boehringer Ingelheim

All makers of heartworm drugs! So of course … the people who make money from heartworm meds want you to take them more often. But that doesn’t mean you have to buy their products. 

So in summary, here’s why I don’t give my dogs heartworm meds:

  • Heartworms are becoming resistant. Even dogs on meds are getting them.
  • Heartworm meds contain toxic ingredients. These toxins make my dogs more likely to get heartworms and other parasites.
  • Heartworm meds can be replaced with herbal remedies.
  • Regular testing can help you identify infections earlier.

Perhaps you’ll consider avoiding these drugs too. Your vet may disapprove. But now you have some information to help you with that discussion! 

References

Knight DH et al. Seasonality of heartworm infection and implications for chemoprophylaxls in the united statesClinical Techniques In Small Animal Practice. 1998 May:13(2).

Adrian J Wooltenholme et al. The emergence of macrolycyclic lactone resistance in the canine heartworm, Dirofilaria immitis. 8 May 2015

Catherine Bourguinat et al. Macrocyclic lactone resistance in Dirofilaria immitis: Failure of heartworm preventives and investigation of genetic markers for resistance. Veterinary Parasitology, Volume 210, Issues 3–4, 2015, Pages 167-178.

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