Heartworm disease can cause serious, long-term damage to the heart, lungs, and blood vessels—often impacting a dog’s health even after treatment is complete. What many pet parents don’t realize is that conventional “preventatives” don’t actually prevent mosquitoes from infecting your pet—they work by killing larvae after exposure. Understanding how heartworm really works, along with both conventional and holistic prevention approaches, is key to making informed decisions for your pet’s health.
For those of you living in climates with four seasons, the temperature has to stay about 57 degrees for an extended period of time for the larvae to develop.
You do not need to use heart worm medication year round unless you live in a tropical climate.
Add fresh garlic and ACV to diet to help repel mosquitoes and try and keep your pets inside when mosquitoes are at their worst.
Pets should be DETOXED every 3 months to rid them off the toxins caused by antibiotics, pesticides, and other environmental causes.
By Langley T. Russell, Beloved Bulldogs, llc
STEP 1: To infect your dog with heartworms, you need mosquitoes (so you need warm temperatures and standing water). More specifically, you need a hungry female mosquito of an appropriate species. Female mosquitoes act as airborne incubators for premature baby heartworms (called microfilariae). Without the proper mosquito, dogs can’t get heartworms. That means dogs can’t “catch” heartworms from other dogs or mammals or from dog park lawns. Puppies can’t “catch” heartworms from their mothers, and moms can’t pass heartworm immunity to pups.
STEP 2: Our hungry mosquito needs access to a dog already infected with sexually mature male and female heartworms that have produced babies.
STEP 3: The heartworm babies must be at the L1 stage of development when the mosquito bites the dog and withdraws blood.
STEP 4: Ten to fourteen days later…
— if the temperature is right, the microfilariae mature inside the mosquito to the infective L3 stage, then migrate to the mosquito’s mouth. (Yum!)
STEP 5: Madame mosquito transmits the L3′s to your dog’s skin with a bite. Then, if all conditions are right, the L3’s develop in the skin for three to four months (to the L5 stage) before making their way into your dog’s blood. But your dog still isn’t doomed.
STEP 6: Only if the dog’s immune system doesn’t rid the dog of these worms do the heartworms develop to adulthood.
STEP 7: It takes approximately six months for the surviving larvae to achieve maturity. At this point, the adult heartworms may produce babies if there are both males and females, but the kiddies will die unless a mosquito carrying L3′s intervenes. Otherwise, the adults will live several years, then die.
In summation, a particular species of mosquito must bite a dog infected with circulating L1 heartworm babies, must carry the babies to stage L3, and then must bite your dog. The adult worms and babies will eventually die off in the dog unless your dog is bitten again! Oh, and one more thing.
In Step 4 above I wrote that heartworm larvae develop “if the temperature is right.” The University of Pennsylvania vet school (in a study funded by Merial) found:
“Development in the mosquito is temperature dependent, requiring approximately two weeks of temperature at or above 27°C (80°F). Below a threshold temperature of 14°C (57°F), development cannot occur, and the cycle will be halted. As a result, transmission is limited to warm months, and the duration of the transmission season varies geographically.”
Here is additional Heartworm information that should set you more at ease. This was written by an expert in dog health and nutrition and based on her experience and posted on Facebook in the group “Bravecto Nexgard Comfortis Simparica Trifexis & others Do They Kill Dogs?”.
It is sad that people are taught that ALL and ANY mosquitoes carry heartworms. That is the biggest fallacy. The simple facts are that no heartworms can be developed in a mosquito unless there is a dog with active heartworms within 2 acres of wherever you are. Second, the temperatures during the day or night have to be OVER 57 degrees for the larvae to develop inside the mosquito. Third, IF the mosquito has bitten a dog with active heartworms, then it has to somehow suck up a microfilaria. They are not that abundant in most dogs so that every bite will end up in sucking up a microfilaria. Even if it does suck one up, the second point then applies. Fourth, it takes a minimum of 10 days for the larvae to develop inside the mosquito. If the mosquito lives that long. They normally live 30 days, if lucky. Only after those 10 days of development inside of the mosquito can a larva be transported onto a dog. Then if the dog’s immune system cannot fight off the larvae, then and only then it has a few months to develop fully into a heartworm.
Even after that, it takes two of the opposite sex to make more microfilaria. And the cycle used by the mosquito still has to continue to bite and re-bite that same dog that is now infected in order to make more adult heartworms within that dog. Microfilaria inside the dog, made by mating, do not make more adult heartworms. The mosquito is required for that.
Even if this now-infected dog is not treated with the awful arsenic Immiticide, the adult heartworms can and will die off within two years, if no more adults are added to its system. During this time, natural methods can and will work easily and rid the dog of the adults it has, and keep others from forming.
If there’s snow on the ground in your area, you DO NOT need heartworm meds right now! If you live where they have mosquitoes nearly all year, you can now administer these “monthly” meds QUARTERLY (every 90 days) based on this article:
Dr. Judy Morgan (2025 Holistic Veterinarian of the Decade): “HEARTWORMS DEEP DIVE! Treatment & Prevention Options.”
Dr. Judy Morgan (2025 Holistic Veterinarian of the Decade): “Heartworm Preventative – Necessity or Not?”
Common Conditions Diagnosed After Use of Flea, Tick, and Heartworm Meds
Please see the graphics below for side effects from frequently prescribed heartworm medications.
Side effect can occur immediately or may manifest several months later after several dosages. These products can cause death within 24 hours or less. Your dog or cat may be diagnosed with one or more of the following:
The use of ivermectin is not advised due to the presence of numerous risks and unknown variables that warrant testing before any usage. Ivermectin is a widely utilized active pharmaceutical ingredient in several heartworm treatments and “preventatives;” however, it is also employed “off-label” for the management of various other parasitic infections. Certain dog breeds exhibit heightened sensitivity to ivermectin, which can lead to toxic and potentially lethal outcomes. It is noteworthy that ivermectin possesses the capability to traverse the blood-brain barrier.
Certain canine breeds exhibit a propensity for a genetic mutation identified as MDR1. This mutation is predominantly observed in herding breeds, such as Collies, Australian Shepherds, and Shetland Sheepdogs, resulting in heightened sensitivity to ivermectin and other medications, increasing the risk of neurotoxic effects. This mutation has also been documented in cats. Clinical signs of ivermectin toxicity may encompass mydriasis, ataxia, tremors, ocular impairment, lethargy, and in critical cases, progression to coma or mortality. Preemptive testing for this mutation is imperative prior to the administration of any products containing ivermectin. Therefore, we just cannot risk recommending ivermectin on this site.
If your pet has ever had a reaction after a vaccine, flea or tick product, antibiotic, or medication, your experience matters more than you may realize. Holistic pet parents are often the first to notice subtle changes — digestive upset, behavior shifts, immune flares, neurological signs, or a general sense that something is “off.”
You do not need proof that a product caused the reaction. You do not need permission from a veterinarian. Reporting simply means sharing what you observed so safety patterns can be recognized and other pets can be protected.
Many adverse events go unreported, especially when symptoms are delayed or considered “mild.” When holistic pet parents speak up, those missing pieces finally get documented.
Antibiotics and other medications such as steroids, NSAIDs, seizure medications, GI drugs, and topical treatments are regulated by the FDA through its Center for Veterinary Medicine.
If your pet experienced vomiting, diarrhea, appetite loss, lethargy, anxiety, seizures, skin reactions, organ stress, or if a medication simply did not work as expected, you can report it directly.
The easiest way is through the FDA Safety Reporting Portal for animal drugs and devices. You can also start at the FDA’s animal reporting page, which explains all available options.
If you prefer to speak with someone, you can call 1-888-FDA-VETS (1-888-332-8387).
Another important step is contacting the medication’s manufacturer. Their contact information is listed on the product label or packaging, and they are legally required to forward adverse event reports to the FDA.
Vaccines are regulated differently from medications. Animal vaccines fall under the USDA, not the FDA.
If your pet had a reaction after vaccination — whether it happened immediately or weeks later — it can and should be reported.
You can report vaccine reactions through the USDA Center for Veterinary Biologics. Information and reporting options are available here.
You can also contact the USDA Center for Veterinary Biologics directly at 800-752-6255.
In addition, vaccine manufacturers should be notified. Their information is typically listed on the vaccine label or your pet’s invoice.
From a holistic perspective, it’s important to remember that vaccine reactions are not always dramatic. Digestive changes, autoimmune flare-ups, chronic itching, behavioral changes, or immune suppression that appear later still matter and are worth reporting.
Flea and tick products require special attention because they are regulated in two different ways, depending on the product.
Some flea and tick products, including many oral chewables and prescription topical medications, are regulated as animal drugs by the FDA. Reactions to these products should be reported through the same FDA channels listed above or directly to the manufacturer.
Other flea and tick products, such as many collars, sprays, powders, and some topical insecticides, are regulated as pesticides by the EPA.
If your pet had a reaction to one of these products, you can find reporting instructions here.
You may also contact the National Pesticide Information Center (NPIC) at 1-800-858-7378, where incidents are documented and forwarded to the EPA. When reporting, include the EPA Registration Number found on the product label whenever possible.
A few reminders for holistic pet parents: trust your observations, even if the reaction was delayed. Mild symptoms still count. You can report even if your veterinarian disagrees. Saving labels, packaging, and lot numbers can be very helpful, but they are not required.
Reporting an adverse event is not about blame or fear. It is about awareness, transparency, and advocacy. Many product warnings, label changes, and safety investigations only happen after enough pet parents speak up.
Your voice helps protect pets everywhere.
Yes. Heartworm is transmitted by mosquitoes, and mosquitoes easily make their way indoors. Even pets that never go outside are still at risk, especially in warmer climates where mosquitoes are active year-round.
Not exactly. Most conventional heartworm preventatives work by killing heartworm larvae after your pet has already been bitten by an infected mosquito. They do not stop the mosquito bite or initial exposure, which is why consistent use and overall health support both matter.
Early symptoms can be subtle and are often overlooked. Dogs may show a mild cough, lower energy, or reduced stamina. Cats can be even harder to read and may show occasional coughing, vomiting, or breathing changes. As the disease progresses, symptoms become more serious and can affect the heart and lungs.
“Heartworm Disease (Natural & Conventional Remedies)” with Dr. Katie Woodley – The Natural Pet Doctor.
“Heartworm in Dogs- is monthly medication needed?” by Dr. Andrew Jones.
“Veterinarian Speaks Out about Heartworm Preventatives” an article about Dr. Karen Becker authored by Susan Thixton.
“Parasiticides⚠️Side Effects of Common Veterinary Drugs” by Dr. Judy Morgan.
Dr. Judy Morgan (2025 Holistic Veterinarian of the Decade): “Credelio Quattro™💊4 in 1 Gamble⚠️Know What You Are Giving Your Dog” by Dr. Judy Morgan.
“Heartworm Preventative” by Dr. Judy Morgan.
The purpose of this product is to assist the body in purging unwanted visitors from the digestive tract. This means it will most likely cause some diarrhea, but diarrhea in conjunction with a disconnection of parasites from the intestinal wall (which may result in a small amount of blood). It is important that you expect your pet to have some level of diarrhea and a small amount of blood when using dewormers – it is important to allow this process.
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