Monday, 4 March 2013

Does Your Dog Really Need to Be On Heartworm Medication? The Truth about Heartworm Prevention, Conventional Preventatives, Natural Safe Alternatives

How do you know if your dog really needs to be on a heartworm preventative? Should you just take your veterinarian's advice or should you double-check on the advice you may be receiving from your Veterinarian? If your dog needs to be on heartworm preventatives are there other things you need to do to ensure the safety of your dog while on the preventative? If you don't know the answers you can be putting your dog's health at risk despite the best of intentions.

In this article...
  1. Risk Assessment;
  2. Consequences and Side Effects;
  3. How to Offset the Risks and Use Natural Alternatives
1.0 The Risk Assessment
  • Who is defining the area you reside in as a 'risk area' for heartworm 
  • What are they defining the risk as low, medium, high?
  • How is the risk level actually defined and estimated?
  • What is the actual source of information on which the assessment is based? 
  • And who is funding the assessment?
What is The Real Risk Assessment?

First verify that your area is truly high risk. If you are in the U.S., the locations that are truly high risk are Florida, parts of Texas, Hawaii and some locations along the Gulf Coast (i.e. New Orleans).  Can you trust the maps generated by the American Heartworm Society (AHS) – the answer is NO. Why? Because AHS is heavily sponsored by 8 (eight) of the major pharmaceutical companies who produce pesticide-laden heartworm preventatives.  You can find-up-to-date maps on the AHS site; however the data which the maps are based on is designed to boost sales of heartworm products and is not reflective of actual reality. 

It seems - at least in North America, that many conventional-practice veterinarians , even those located in very low risk areas for heartworm infection are actively and intensely pushing pesticide-based heartworm medications on their clients.  


Well primarily because the big pharmaceutical companies (i.e. Pfizer) have aggressively and expertly marketed pesticide laden heartworm products to veterinarians. The marketing campaigns base their 'facts' on skewed data, incomplete reporting (including side effects, testing results, comparisons and alternatives). Unfortunately the pharmaceutical companies’ objective is not the health of your pet; it is instead their desire for profit. 

Many of the veterinarians pushing these products on their clients are truly not aware of the truth about these products - the short and long-term deleterious side effects (immune system suppression, organ failure, cancer, etc.). In addition very few conventional veterinarians have much knowledge about diet/nutrition and alternate, natural preventatives. And yes, of coarse veterinarians do make  money off of the vending, and protocol around sales of heartworm prevention products.

Conditions Must Be Exact for A Dog to Be Infected with Heartworm

Ambient air temperature conditions must be perfect for the heartworm larvae to first survive in the mosquito, and then under the dog's skin during stages L-1 thru to L-4 of development

During larvae development within the mosquito, the ambient air temperature must remain above 57 degrees Fahrenheit - day and night for a minimum of two weeks. If at any time during this stage in the larva's life, the temperature drops below 57 degrees F, development of the larvae is stopped and must start all over again if and when the temperature increases. The larvae must reach the L-3 development stage before it can infest a dog.

At stage L-3 of development heartworm larva are left in a tiny droplet of mosquito saliva which is deposited next to the mosquito bite location on the dogs skin

Once again the ambient air temperature must be right, and the humidity content in the air must be sufficient to avoid evaporation of the saliva droplet. The larvae canot enter the dog's body without the saliva. To enter into a dog's body, the L-3 larva must swim through the droplet and thereby makes its way into the actual hole made by the mosquito bite. Once inside the dog the L-3 larva spends the next 2 weeks developing into an L-4 stage larva. At L-4 the larva is still living just under the dog's skin, were it will remain and continue to develop into L-5 over the next 3 to 4 months. At L-5 stage of development the larva then enters the dog's blood stream, where it migrates to the heart and pulmonary arteries. Five to seven months after entering the dog's body the larva will mate if both female and male larva is present. The mating of the larva results in the production of the heartworm (the microfilariae).
How Do Conventional Heart Worm Preventatives Work?

Heartworm preventatives don’t stop your dog from being:
  • Bitten by a misquoto;
  • By being infected by heartworm.
Instead, pesticide-based heart worm preventatives poison and subsequently kill the larvae once it (the larvae) is in your dog’s system. Blood tests are recommended prior to your dog taking heartworm preventative because if your dog is already infected with larvae, ingesting the preventative will not kill the worms - a different treatment will be required if your dog is already infested.
 Because of the growing immunity of the parasites to the currently used active chemicals – if you want or need to put your dog on these drugs; blood testing once a year may no longer be sufficient. To be effective Blood testing would need to be done twice a year.

The real key to preventing heart worm is to make your dog's skin and blood undesirable to a mosquito. A healthy dog's blood has a bitter taste to parasites, an unhealthy dog's blood has a sweet taste to parasites. This is where Organic Apple Cider Vinegar, Fresh Lemon, Garlic, etc. become very important attributes to a dog's diet - more on that further below.

2.0 Consequences and Side Effects of Use
In Broad Terms - Risk to The Canine Species

The overuse of pesticide-based heartworm preventatives has resulted in an ever-increasing ineffectiveness of these mendicants as the parasites have built-up an immunity to the chemicals. Meaning – just because your dog is on a preventative is no longer an assurance that it cannot acquire the heartworm parasite. The pharmaceuticals are in the process of developing a new round of stronger pesticides to cope with the growing immunity of the parasites. These stronger pesticides will eventually create a new immunity in the parasites – a vicious circle which will see our dogs health further impacted.

In Specific Terms - Risk to The Individual Dog
Pesticide-based heartworm preventatives contain very strong pesticides.  According to the American Veterinary Medical Association...
  • 65% of adverse drug reactions, and 
  • 48% of all reported deaths - resulting from drug interactions are casued by conventional pesticide-based heartworm preventatives.
As an example,the active ingredient in Heart Guard is Ivermectin. Ivermectin has many potential side-effects... 
  • Aggressive behaviour (sudden aggressive behaviour); 
  • Autoimmuine disorders;
  • Depression;
  • Diarrhea;
  • Difficulty breathing;
  • Dizziness;
  • Fertility problems; 
  • Fever;
  • Lethargy;
  • Liver problems;
  • Loss of appetite;
  • Nose bleeds,
  • Paralysis;
  • Pneumonia;
  • Thyroid problems;
  • Tremors;
  • Seizures;
  • Skin eruptions; 
  • Sudden death; 
  • Vomiting;
  • Weakness    
The other active ingredients used by other chemical-based heartworm preventatives have many of the same or similar side effects. At the bottom of this article you can look at a comprehensive list of various parasite medications, side effects and cautions.  

Have you ever stopped to think about why the labels on such products warn you to avoid contact with your skin and wash your hands directly after touching the product? It is because the active ingredients are powerful pesticides.

The active ingredients are toxic poisons which:
  • Weaken your dog's immune system;
  • Force your dog's liver and kidneys to work over-time to eliminate the toxin from his/her blood stream.
While on these chemical-based preventatives, your dog's natural system is not at its normal efficacy level - as such contact with bacteria and viruses that would not normally be able to harm a healthy dog have a better chance of making your dog seriously ill.

Taking steps to boost your dog's immune system is doubly important when your dog is on chemical-based heartworm preventatives.
Coyotes, foxes and wolves are a good example of how a species appropriate diet (meat, fat, some berries, grasses and herbs) protects healthy animals from infection. Some coyotes and foxes have been identified as having the capability to fight-off infestations of heartworm and/or remain a host to the worm, while keeping the infestation minor enough so that his/her life (the host fox or coyote) is not in mortal danger. This is a natural response by a healthy immune system.

So why are our domesticated dogs at such high risk? Domesticated dogs today:
  • Are exposed to multiple times daily to toxins (ingested, inhaled, surface contact) - more on that further below) on a daily basis;
  • As a result the dog carries a constant and heavy toxic load, weakening his/her immune system and making a hospitable environment for a mosquito and it's larvae.
In general dogs that die from heartworm are dogs that are:
  • Fed highly processed food diets;
  • Being over-vaccinated;
  • Are constantly treated (and unnecessarily so) with immune system suppressive drugs such as antibiotics. 
The infestation is not the trigger for death, the weakened immune system - that first leads to the infestation, and then is incapable of fighting the expansion of the infestation, kills the dog. The key is to keep your dog's immune system healthy.

Whether you are in a Low, Medium or High Risk Zone
Here is What You Can Do…

3.0 Off-Set the Risks and Use Natural Interventions

Your dog's first defense against parasites and disease is a strong immune system...

Don’t Over-Inoculate Your Dogs 
From rabies to leptospirosis ('lepto') and everything in-between conventional-practice veterinarians over-inoculate dogs (again lack of knowledge on their part and in other cases greed). Inoculations suppress your dog’s immune system, contain toxic ingredients, cause cancer, can cause neurological issues, cancer, etc. Humans do not need to be constantly inoculated and neither do canines.

Don’t Put Your Dog’s On Antibiotics or Steroidal Treatments Unless it is Really Necessary

I do not put my dogs on unnecessary or repeated courses of antibiotics or steroidal treatments (which suppress the immune system). Ten of the top ten reasons for bringing a dog to the veterinarian are diet are examples of how to holistically treat and remedy a few of those top 10 items....

Avoid and Reduce Your Dog's Exposure to Toxins and Carcinogens
Avoid exposure to harmful chemicals in their food and environment...
Use Safe Non-Toxic Topical Alternatives to Repel Parasites and Insects

Get Your Dog on a Species Appropriate Diet
  • Option one: raw diet;
  • Option two -  raw and cooked foods;
  • If you do not want to feed your dog option one or two then find a no grain, no toxins, no carcinogens, no GMO, truly good quality dry dog food - and you  will need to supplement with other items such as a good probiotic, omega-3 fatty acids... 
Supplement on a Daily Basis with Other Food Stuffs that Promote Overall Health and Boost the Immune System, i.e....
Don’t have your dog on chemical based flea, tick and/or other parasite mendicants during the week that you give your dog the heartworm preventative. The combined toxic load on your dog’s system becomes dangerous to organ and immune system function – you would be putting your dog at risk of acquiring serious health issues.

Follow-up the treatment with safe liver-detox agents, for example:
  • Milk thistle, 
  • Finely chopped, fresh non-GMO beets;
  • Fresh lemon;
  • Fresh chopped, or minced garlic;
  • Organic dark leafy greens with flax oil drizzled on top;
  • Organic fresh or frozen mashed berries with flax oil drizzled on top.

For Those Who would Like to See More Detail 

The following chart provides a few examples of the synthetic compounds typically found in off-the-shelf and veterinarian prescribed parasite preventative medications. This will provide you with a good overview of popularly prescribed and off-the shelf parasite preventatives.

Active Ingredient Target Side Effects Used In
Amitraz Ticks, Mange, Scabies Can cause high blood sugar (hypoglycemia), low blood pressure (hypotension), low body temperature (hypothermia), sedation Proventic Commonly used in mange dips and tick collars. Do not use on dogs under 12 weeks of age, do not use on aged, sick, medicated, pregnant or nursing dogs
Arylheterocycles (most common - Fipronil) Fleas, Ticks Can cause irritation - I was unable to find details on what was meant by ‘irritation’…i.e. skin irritation? Frontline Do not use on dogs under 8 weeks of age, sick, medicated or aged dogs
Dinotefuran Fleas Can cause immune system toxicity. Vectra Do not use on debilitated, aged, medicated, pregnant or nursing dogs, or dogs known to be sensitive to pesticides, aged, sick, pregnant or nursing
(methoprene, fenoxycarb, pyriproxyfen)
(lufenuron, diflubenzuron)
Fleas Can cause vomitting, diarrhea Program, Preventic Read the label - age of puppies products can be used on varies, do not use on aged, sick , medicated, pregnant or nursing dogs
Can cause drooling, skin irritation and may cause miscarriages and skeletal deformities. Advantage II Do not use on dogs that are: aged, nursing or pregnant, sick or under 7 weeks of age.
Ivermectin Heartworm, Neurotoxicity - depression of the nervous system followed by ataxia. Dogs with defects in P-glycoprotien can suffer severe poisoning Heartgard, Most Collies cannot tolerate this substance and should not be given meds that include Ivermectin. Do not use on dogs under 6 weeks of age, aged, sick, medicated or underweight
Milbemycin oxime Roundworms, Hookworms Can cause stupor, tremor and ataxia Interceptor, Sentinel Not to be used on Collies or other herding breeds. Often used in products that include Ivermectin. Check the label of the specific product for puppy age restriction. Do not use on breeding, pregnant dogs or dogs with epilepsy
Nitenpyram Blow Flies, Fleas, Maggots Can cause Lethargy/depression, vomiting, itching, decreased appetite, diarrhea, hyperactivity, lack of coordination, trembling, seizures, panting, allergic reactions including hives, vocalization, salivation, fever, and nervousness Capstar Should not be used on pregnant and nursing dogs
Pyrantel pamoate Roundworms, Hookworms
Can cause facial swelling, hives, scratching, sudden diarrhea, vomiting, shock, seizures, pale gums, cold limbs, or coma.

Usually used in combination with Ivermectin

Fleas, Ticks, Lice, Mites, Misquitoes
Can cause tremors, depression, convulsions, death
Bio Spot Flea and Tick Spray or Spot on Flea Control Do not use on dogs that are aged, sick, medicated, pregnant or nursing.  Do not use spray on puppies under 12 weeks of age, do not use oral tablets on dogs under 6 months of age

Fleas and Ticks
Can cause drooling, tremors, vomiting, seizures
K9 advantix II Do not use on dogs that are: aged, nursing or pregnant, sick or under 7 weeks of age.
Praziquantel Tapeworms
Can cause drooling, sudden diarrhea, loss of appetite, lethargy, staggering, vomiting

Selemectin Heartworm, Fleas, Mange, Mites, Ticks, Parasites
Can cause hair loss, skin issues, and burns, permanent immune system damage, etc.
Revolution Do not use on puppies under 6 weeks of age
Spinosad Fleas
Can cause loss of appetite, diarrhea, vomiting
Comfortis Do not use on pregnant dogs or dogs with epilepsy, dogs under 14 weeks of age

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Article and graphics by Karen Rosenfeld 


  1. Thank you for trying to educate people about this. I have four dogs, and i refuse to go along with this over immunization movement of our pets. We were awaken to the facts when our boston terrier ended up with blood cancer at three, and she was given everything recommended by the vet prior. I also do not conform to the garbage we call dog food, so I make their food at home from scratch. I am currently trying to find a holisitc vet, as I do not want to get forced into doing anything to my pets I don't believe in. Not enough people do research and often look at me like I have two heads when I try and explain. Thank you again.

    1. You have one head and it is a good one :>) The American Animal Hospital Association (AAHA)updated guidelines for vaccinations 2 years ago in recognition of the fact that annual inoculations are not necessary and are in fact health threatening. In the updated guidelines the AAHA specify that non-rabies core vaccines (distemper and parvovirus) are good for (provide immunity for) a minimum of 5 years and the vaccine for adenovirus is at minimum good for 7 years. The AAHA set the requirement for core vaccinations at every 3 years - and have admitted that even that was over-vaccination. Despite the issuance of the new guidelines (2 years ago!) by the AAHA many veterinarians are holding fast to the old allopathic protocol of annual inoculations. The only vaccine required by law is rabies and rabies inoculations were also recommended to a 3 year protocol, however an overwhelming number of veterinarians continue to insist on annual inoculations - the real reason - reluctance to give up the income annual inoculations bring in. Cheers, Karen

  2. I have 4 dogs and one is Heartworm positive.The vet prescribed Advantage Multi but,it doesn't work very good on my dog and he is allergic to fleas, what can I give them that is natural,no chemicals that will really work and be safe for them?

    1. Hi Elizabeth - going natural must be done holistically - with a properly designed diet nutrition and topical plan - for that you would need to purchase consultation time.

  3. Wow, this information makes so much sense. I have 2 german shepherds. My vet insists on keeping them on heartworm preventative all year round. I kept trying different brands but my sheps would vomit each time and just lay on the floor panting. I would feel horrible giving this to them because I'm told they must have this to prevent heartworm and at the same time I feel like I'm hurting them with these meds. It's so sad that when we love and care for our animal friends and want to do our best keeping them healthy there's those who we trust (the vets) who won't fully educate us on these chemicals they push on us to give to our pets

  4. I have a dog who became extremely ill shortly after a round of "safe" de-worming. Even if I didn't have my doubts about flea/tick/heartworm medication (hint: I do!), I wouldn't be using them on this particular dog. Even DE made him ill. Since tweaking his (home prepared) diet, focusing on the health of his immune system, and addressing his emotional balance, fleas don't bother him.

    Everywhere I go, I read or hear people saying "(insert topical flea control product) just isn't working anymore! I treat monthly and my dog is still infested!" Yes, address the underlying issues first and ditch the poisons. It also makes me wonder, since we can visually SEE if a flea control medication is or is not working, how do we know if the heartworm prevention we're using is working or not? These medications give us all a false sense of security; taking a holistic balanced approach just makes so much more darned sense.

  5. Great article.


Important Note

1.0 Use of Foods, Herbs, Alternative Medicines:

Safe use of items and protocols in the article above, is your sole responsibility.

Foods, herbs and alternative medicines have health issue, condition and conventional drug interactions. Safe use of all substances and protocol are your responsibility.

Before you use any substance or protocol do your research. Check for cautions, contradictions, interactions and side effects. Do not use substances or protocols not suitable to your animal's individual circumstances.

If your animal has an underlying condition substances and protocols may conflict.

2.0 Definition of Holistic…

Food, herbs, alternative medicines are NOT ‘holistic’ they are a substance and MAY, or may NOT be ‘NATURAL’.

If you use a ‘natural’ substance (ie. an herb) you are using a natural substance, not a holistic substance.

Holistic is not defined by use of one or several substances. Holistic is an approach.

Definition of “holistic” from the Cambridge Advanced Learner's Dictionary & Thesaurus © Cambridge University Press


"relating to the whole of something or to the total system instead of just to its parts"

"Holistic medicine attempts to treat the whole person, including mind and body, not just the injury or disease."

Holistic is a way of approaching life, and within that health, and well-being.

3.0 Expectation a natural substance remedies a health or behavioral situation.

A natural substance used to treat symptoms. But, if factors causing the underlying issue remain you do not have a remedy.

Remedy requires a comprehensive approach. It is necessary to identify root cause. Remove items that trigger, cause or otherwise contribute to issues. Holistic approach includes design, implementation to treat, remedy and maintain long-term health.

4.0 Leave a Comment

I review all comments and publish those deemed appropriate for this site.

I answer questions deemed appropriate when I have time to do so.

Wishing your dog and cat the best of health!

Karen Rosenfeld
Ottawa Valley Dog Whisperer
Holistic Behaviorist - Dogs
Holistic Diet Nutrition Wellness Adviser – Dogs and Cats