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Everything You Need To Know About Heartworm In Dogs And Natural Ways To Treat And Prevent It.

My name is Clarissa Dery, owner of Four Leaf Clover. I'm also a Certified Canine Nutritionist and a Certified Canine Herbalist. In this blog, I'll discuss:

- The problem with heartworm drugs

- Reported side effects with heartworm drugs

- How dogs get heartworm

- 4 Natural ways to prevent your dog from getting heartworm

Holistic veterinarian Glen Dupree DVM 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 their 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.

Your dog’s immune system is supposed to protect their body from parasites. A well-tuned immune system is the difference between a few heartworms that your dog’s body keeps in check … and a large heartworm load that affects your dog’s health. That’s what Dr. Dupree is talking about. A big part of protecting your dog from heartworm is protecting its immune system.

Here’s why I don’t give my dogs heartworm meds:

· Heartworms are becoming resistant to heartworm medication (dogs on heartworm medication are still getting them).

· Heartworm meds contain toxic ingredients with dangerous side effects.

· Heartworm meds can be replaced with herbal remedies.

· Regular testing can help you identify infections earlier.

The Problem With Heartworm Drugs

Heartworm meds are neurotoxins - They kill larvae by paralyzing them. So it’s no wonder they can also damage your dog. In the side effects below, you’ll see they often include 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 entire life.

Reported Side Effects of Common Heartworm Medications For Dogs

HEARTGARD And TriHeartPlus (ivermectin) Depression/lethargy, vomiting, anorexia, diarrhea, mydriasis, ataxia, staggering, convulsions, and hypersalivation.

NTERCEPTOR (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, muscle tremors, pruritis, urticaria, erythema, ataxia, and 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 ProHeart 6 from the market in 2004 because of deaths. But they’ve brought it back and have introduced ProHeart 12.*

If your dog has a serious side effect it is very hard to treat because the drugs are in his body for 6 - 12 months. And, 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 like heartworms.

Also, heartworms are becoming resistant to heartworm meds. The more we use the drugs, the less effective they become.

How Do Dogs Get Heartworm

The ONLY way your dog can get heartworms is from a mosquito bite. He can’t catch heartworms from another dog or another animal. It’s also worth noting the difference between Heartworm Microfilariae And Larvae. People (even some vets) often use these words interchangeably. Microfilariae and larvae are both young heartworms but in different stages of development. Microfilariae are heartworm babies and 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.


1. The mosquito picks up heartworm microfilariae by biting a heartworm-infected animal.

2. Microfilariae grow into larvae in the mosquito.

3. The mosquito with heartworm larvae bites your dog, leaving larvae in him.

4. Over about 6-7 months, the larvae can grow into adult heartworms in your dog.

5. Eventually, the adult heartworms start breeding creating microfilariae.

Natural Heartworm Prevention For Dogs

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. Because of the way heartworms develop, 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 why it’s best to focus on the immune system because 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. Therefore, you can strengthen your domestic dog’s health with a natural lifestyle:

· Feed a natural, 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 him plenty of exercise

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 such as Four Leaf Clover’s Immunity Boost powder

#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 such as Wondercide products

  • Feed fresh garlic to help repel 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.

#3 Use Herbal Heartworm Protection

There are some pre-made herbal heartworm products you can buy such as Amber Naturalz Clean Heart. Please be aware that 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 You can 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 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.

How Heartworm Tests Work

There are 3 different types of heartworm tests.

1) 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 antibodies at all due to “antigen-antibody complexes” in the blood.

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

2) Microfilariae Test This test will show if there are microfilariae in your dog’s system. 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. 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…

3) 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.

In conclusion, my goal is to educate pet parents to be the best advocates they can be for their dogs. Your vet may disapprove, but now you have some information to help you with that discussion.


Knight DH et al. Seasonality of heartworm infection and implications for chemoprophylaxls in the united states. Clinical 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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