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Dangers of Flea, Tick, and Heartworm Preventative Medications

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Dangers of Flea, Tick, and Heartworm Preventative Medications

Fleas and ticks are a considerable nuisance, primarily if you reside in an area where they are prevalent. Pharmaceutical companies have developed and manufactured multiple products to combat flea and tick infestation, but at what cost to your dog? The active ingredients in the medications are neurotoxins that supposedly only negatively impact the offending pests. But how can that neurotoxin not have adverse side effects on your dog?

Active Ingredients in Flea and Tick Preventatives

Flea and tick preventatives typically contain active ingredients that are effective at repelling or killing fleas, ticks, or both. The specific active ingredients can vary depending on the product formulation and the application method: topical, oral, or collar. Some common active ingredients found in flea and tick preventatives for pets include:

  • Fipronil: Fipronil is a broad-spectrum insecticide that disrupts the nervous system of fleas and ticks, leading to their paralysis and death. It is commonly used in topical spot-on treatments for dogs and cats.
  • Imidacloprid: Imidacloprid is an insecticide that acts on the nervous system of fleas, causing paralysis and death. It is often combined with other active ingredients, such as fipronil or permethrin, in topical spot-on treatments.
  • Permethrin: Permethrin is a synthetic pyrethroid insecticide that repels and kills fleas and ticks on contact. It is commonly used in topical spot-on treatments and flea collars for dogs but should never be used on cats. 
  • Pyrethrin or Pyrethroids: Pyrethrins are natural insecticides derived from chrysanthemum flowers, while pyrethroids are synthetic versions of pyrethrins. They affect the nervous system of insects and are commonly used in topical spot-on treatments and flea collars for dogs and cats. Flumethrin is a synthetic pyrethroid used in flea collars.
  • Selamectin: Selamectin is a parasiticide that belongs to the avermectin class of compounds. It is used in topical spot-on treatments for dogs and cats to prevent heartworm disease, kill fleas, and treat and control ear mites and certain types of mange.
  • Spinosad: Spinosad is a naturally derived insecticide that targets the nervous system of fleas. It is used in oral chewable tablets for dogs to kill fleas and prevent flea infestations.
  • Lufenuron: Controls flea infestations by preventing eggs from hatching and the flea shell from developing. Lufenuron is used in both oral and spot-on treatments for dogs. 
  • Tetrachlorvinphos: Used as a medication, insecticide, and nerve agent as a weapon. Used as an oral larvicide in livestock and against flies in dairy. They kill fleas, ticks, lice, chiggers, mites, spiders and wasps.
  • Methoprene: A slow-acting insecticide that interferes with the growth cycle of an insect to prevent it from maturing and reproducing.
  • Pyriproxyfen: A chemical agent often used in pesticides, it mimics a natural hormone in insects and prevents eggs from hatching.
  • Isoxazolines: Fluralaner, afoxolaner, lotilaner, and sarolaner are the most commonly used insecticides and acaricides in the form of oral chewable tablets for dogs to kill fleas and ticks and prevent flea and tick infestations. Isoxazolines are valued for their rapid onset of action, efficacy, and duration of protection against fleas and ticks. 

Dangers of Isoxazolines 

Isoxazolines are the most commonly used flea and tick preventative because they are the active ingredient in the chewable pills veterinarians prescribe. The ease of dosing your dog and the almost immediate action of the drug make them very popular with dog parents. 

One of the most well-known isoxazoline-based pet products is Bravecto®, which contains fluralaner as its active ingredient. This medication is available for both dogs and cats and is used to control flea and tick infestations. Other common brands that contain isoxazoline compounds include NexGard®, Simparica®, and Credelio®.

Isoxazolines target specific parts of the nervous system in fleas and ticks. They lock onto specific receptors in these pests' brains and nervous systems. These receptors, called GABA receptors and GluCl, help regulate how nerve cells communicate. When isoxazolines latch onto these receptors, they stop them from working correctly.

One of the main things isoxazolines do is interfere with a chemical called GABA. GABA is like a "calm down" signal in the flea's nervous system; as isoxazolines block GABA receptors, the nerves of the flea become overactive.

Isoxazolines also impact another part of the nervous system called glutamate-gated chloride channels (GluCl). This helps control the flow of specific ions in the nerves, which affects how nerve signals travel. By interfering with GluCl, isoxazolines cause impaired movement and, ultimately, paralysis of fleas and ticks.

Side Effects of Isoxazoline on Dogs

Isoxazolines function on a systemic level. They are absorbed into your dog's bloodstream, potentially impacting his entire body. Fleas and ticks encounter the chemicals by feasting on your dog's blood.

Although the toxicity of isoxazolines is supposed to affect invertebrates only, there are many reports of dogs being severely impacted. Dogs exhibited signs of neurological toxicity, including generalized loss of muscle coordination (ataxia), tremors of the head and body, muscle twitching, and swallowing difficulties. Other clinical signs include:

  • Random stumbling or falling
  • Vomiting
  • Diarrhea
  • Lack of appetite
  • Skin rash or irritation
  • Lethargy

A warning was sent out in September 2018 by the FDA to alert pet owners and veterinarians to warn them of the potential for neurological adverse events in dogs and cats when treated with drugs in the isoxazoline class. The FDA has since requested that manufacturers of isoxazoline products include new label information highlighting neurological events seen consistently in dogs exposed to isoxazoline. Subsequently, the FDA updated the alert with additional manufacturer information in April 2019, August 2019, and October 2019.

Poisoning Fleas and Ticks and the Dog

Isoxazolines are considered safe because of the size difference between your dog and the fleas and ticks. It is toxic to fleas and ticks, but the dose is too low to harm your dog. Although that may be true for some dogs, many others are adversely impacted by the toxic substance, despite the small amount, especially since you are encouraged to give your dog preventative for months at a time, allowing no time for the body to recover from the poisonous substance.

Between January 2013 and September 2017, the FDA recorded adverse events (AE) related to certain flea control products used in dogs. These products contain isoxazolines, such as afoxolaner (found in Nexgard®), fluralaner (found in Bravecto®), sarolaner (found in Simparica™), and others. During this time, there were 32,374 reported AE in dogs. Some of the reported events included deaths (2.4% for afoxolaner, 2.5% for fluralaner, and 3.2% for sarolaner) and seizures (6.9% for afoxolaner, 2.8% for fluralaner, and 20.5% for sarolaner). 

Flea and Tick Collars are Also Dangerous

Flea and tick collars are worn constantly with dangerous chemicals in continual contact with our dog as they enter your dog's dog via the skin. Although your dog does not consume the chemicals, these collars discharge chemicals into the area around your dog's neck and skin. The substance then circulates in the bloodstream. When a flea or tick feeds on your dog's blood, it ingests the toxin and eventually dies. This happens over months while your dog is wearing the collar.

These collars are for external use only. But your dog doesn't know that. He licks his skin and fur to keep himself clean. He'll easily swallow the pesticides in the collar, which will disperse throughout his coat and skin over several months.

Because your dog is a mammal, pyrethroid pesticides like flumethrin are tolerated far better by him than by insects like fleas. Toxicity is 1,000 times higher in insects. However, the consequences can be catastrophic with your dog's constant exposure through his skin and respiratory system, especially if there are open wounds in the area.

EPA Investigates Seresto® Flea Collars

A recent Environmental Protection Agency (EPA) report, dated February 29, 2024, sheds light on the concerning incidents associated with the use of Seresto® flea collars. The issues with Seresto® first surfaced in 2012 but garnered significant attention in March 2021 when news media reported over 1,500 pet deaths and numerous illnesses linked to the collars. 

Over the span of a decade, from 2012 to 2022, the EPA received upwards of 100,000 incident reports concerning Seresto® pet collars. By November 2022, the EPA had received over 2,500 reports of pet deaths and nearly 900 reports of human pesticide incidents related to Seresto® collars.

Prompted by these alarming reports, the EPA initiated a comprehensive investigation into Seresto®. In 2022, an EPA subcommittee published a report outlining the agency's awareness of the incidents and the potential harm associated with the collars. An independent review conducted in 2016 had already suggested that the collars "probably or possibly" caused 45% of the reported pet deaths.

Despite acknowledging that up to 45% of the reported incidents were likely attributable to the product, the EPA has not mandated the discontinuation of Seresto®. Furthermore, the EPA has not provided assurance regarding the safe use of the product. Instead, they simply recommend that consumers remove the collar from their dogs if clinical signs of adverse effects occur.

Natural Options for Flea and Tick Prevention

Although natural alternatives often do not work as quickly as pharmaceuticals, they can provide a healthier option for treating and preventing external and internal parasites.

Routine Grooming and Cleaning

If your dog has a flea infestation, bathing, grooming, washing all dog bedding weekly, vacuuming, and general overall cleaning are required for the duration of flea season in your area. A natural shampoo like citrus castile soap can be used each week, followed by a final rinse with ACV. For this rinse, use 1 part vinegar and 10 parts water. Prevention is always preferred.  

Essential Oils for Fleas and Ticks

While some essential oils have been suggested as natural flea repellents for dogs, it is crucial to approach their use cautiously. Essential oils can be potent and may cause adverse reactions in dogs if misused or in high concentrations. Some essential oils are also toxic to dogs and should be avoided altogether. The following are a few essential oils that are generally considered safe for use as flea repellents for dogs when appropriately diluted (Mix 3-6 drops of essential oil in 1 ounce of carrier oil) and used in moderation:

  • Lavender Oil: Lavender oil has insect-repelling properties and a pleasant scent. It's often used to help repel fleas and can also have a calming effect on dogs.
  • Cedarwood Oil: Cedarwood oil is known for its flea-repelling properties and can be used in natural flea sprays or shampoos for dogs.
  • Peppermint Oil: Peppermint oil has a strong scent that fleas dislike. It can be diluted and applied as a spray or added to homemade flea collars.
  • Lemongrass Oil: Lemongrass oil has natural insect-repelling properties and can be effective against fleas. It's often used in combination with other oils in homemade flea-repellent recipes.
  • Eucalyptus Oil: Eucalyptus oil can help repel fleas and has a refreshing scent. However, it should be used in low concentrations and avoided in dogs with respiratory issues.

Consulting with a canine herbalist for guidance is recommended. They can advise on proper dilution ratios and any potential risks or contraindications based on your dog's health status. You should also perform a patch test on a small area of your dog's skin to check for adverse reactions before applying the oil more broadly. 

Diatomaceous Earth as a Natural Preventative

Diatomaceous earth (DE) is a fine powder made from the fossilized remains of diatoms, a type of algae. It is commonly used in organic gardening and pest control due to its abrasive texture and ability to absorb moisture. Some people also use food-grade diatomaceous earth as a natural flea and tick repellent for dogs.

The idea behind using diatomaceous earth for flea and tick control is that the microscopic particles in the powder can physically damage the exoskeletons of insects, causing them to dehydrate and die. Tips for using DE for flea prevention include:

  • Only use food-grade diatomaceous earth for pets. This type of DE is considered safe for consumption and is less likely to cause irritation or respiratory issues when applied to your dog's fur.
  • When applying diatomaceous earth to your dog, avoid getting it in their eyes, nose, or mouth, as it can be irritating. Applying it outdoors or in a well-ventilated area minimizes powder inhalation.
  • Diatomaceous earth loses its effectiveness when wet, so it may not be suitable for dogs that spend much time in water or wet environments.
  • DE is not a long-lasting solution, as it can be easily washed or brushed off your dog's fur. You may need to reapply it regularly for continued flea and tick control.

Diatomaceous Earth can also prove helpful. Internal parasites like worms can be controlled by mixing diatomaceous earth, also known as DE, with food. Make sure you have the proper diatomaceous earth for your dog. The DE must be food-grade diatomaceous earth. Garden and pool filter products are produced differently and can be hazardous. 

DE also shouldn't be inhaled; small particles could damage your dog's lungs (and yours). Under a microscope, they look like microscopic pieces of glass, so they are utilized as a natural option for parasite relief. When placed on your dog's fur, it cuts the parasite and dehydrates them.

Diatomaceous earth can also help rid your dog of roundworms, whipworms, pinworms, and hookworms. It can work in as few as seven days if you feed it daily.

However, diatomaceous earth should be fed for at least 30 days to be most effective. This will ensure that any newly hatching eggs are eradicated. It will also catch the worms cycling through the lungs and back to the stomach.

Garlic as a Flea and Tick Preventative

For more than 20 years, there has been a misconception among the dog parent community that garlic is toxic for dogs. However, the claim was founded on a study conducted in 2000 that force-fed dogs via a nasogastric tube extremely high doses of garlic, doses that no dog would ever consume on its own! Not only is garlic not toxic for dogs, but it also has many medicinal benefits, including flea and tick prevention, when provided at the correct dosage.

For more than 20 years, there has been a misconception among the dog parent community that garlic is toxic for dogs. However, the claim was founded on a study conducted in 2000 that force-fed dogs via a nasogastric tube extremely high doses of garlic, doses that no dog would ever consume on its own! Not only is garlic not toxic for dogs, but it also has many medicinal benefits, including flea and tick prevention, when provided at the correct dosage.

Feeding garlic during flea and tick seasons can keep infestations under control. Begin feeding garlic daily at least one month before the flea and tick season begins. The garlic takes 2-3 weeks to build up in your dog's natural coat oil and repel fleas and ticks. Continue to feed garlic throughout the flea and tick season.

Garlic must be minced and fed to your dog within 20 minutes for the full effect of the active ingredient, allicin. Due to the differences in clove size, the teaspoon measurement of minced garlic is more accurate, especially for smaller dogs.

  • 5lbs: ⅙ tsp
  • 10-15 lbs: ½ tsp
  • 15-40 lbs: 1 tsp
  • 40-75 lbs: 2 tsp
  • 75+ lbs: 3 tsp

Treating the Yard With Nematodes

Nematodes, Steinernema feltiae, and Steinernema carpocapsae, natural predators of fleas, can be sprayed onto your yard to reduce the flea population drastically. The nematodes naturally live in the soil, attack fleas and insect larvae, break their lifecycle and inhibit the development of adult fleas. The nematodes are safe and harmless to beneficial garden insects such as ladybugs, lacewings, praying manti, and earthworms. 

These microscopic worms prey on flea larvae and pupae, effectively disrupting their life cycle and eliminating them before they mature into biting adults. Their presence in your yard ensures that the flea population is controlled, reducing the risk of re-infestation. 

The nematodes are easily dispersed in your yard using a sprayer or a watering can. Once released, they seek out flea larvae and pupae, ensuring that the next generation of fleas is effectively eliminated.

Fleas are not the only pests that can be controlled with nematodes. Codling moth, Subterranean Termites, German cockroach, Asian cockroach, American cockroach, Fruit fly, Armyworm, Beet armyworm, Cucumber beetle, Artichoke plume moth, Cutworms, Sod webworm, Earwigs, Black cutworm, Mole cricket, Corn earworm, Cotton bollworm, Tobacco budworm and leafminers, and Iris borers are also destroyed.

Traditional Heartworm Prevention

Heartworms are a dangerous and scary disease. Most people struggle with the concept of not providing a pharmaceutical preventative due to the severity of the disease. However, alternative preventative methods can be used successfully, especially in areas with minimal reported cases of heartworm.  

Mosquitoes are the carriers of heartworms. Microfilaria, or tiny heartworm larvae, circulate in the blood of an infected dog and are ingested by the mosquito upon feeding. Dogs are natural hosts for heartworms. When an infected mosquito bites a dog, the heartworm microfilaria is deposited into the bloodstream. They continue their growth cycle within your dog until they reach fully mature worms in the heart.

A heavy heartworm infestation can be hazardous to treat. When an infected dog is given treatment, the worms die within the chambers of the heart. They break up into smaller pieces that pass through the lungs and other areas of the body, causing severe inflammation and potentially respiratory collapse. Not all dogs can recover from their treatment, so prevention is the best approach.

Ivermectin (Heargard®), milbemycin (Interceptor®), and selamectin (Revolution®) are the most common heartworm preventatives. Although severe adverse reactions are uncommon, there are potential adverse reactions to the preventative, including: 

  • Depression
  • Lethargy
  • Vomiting
  • Diarrhea
  • Convulsions
  • Rapid breathing
  • Allergic reactions
  • Hypersalivation

Because heartworm-preventative medications have been in use for several decades, the parasite is developing a resistance to its effects. Your dog may not be protected or claimed by pharmaceutical companies.

Natural Heartworm Prevention

You can purchase prepared herbal heartworm products. Natural heartworm preventatives will not have claims of heartworm disease prevention on the labels due to the FDA restrictions on advertising natural products as preventatives. Most products will carry claims to protect your dog during mosquito season.

Natural preventative products may contain the following ingredients: 

  • Hawthorn: Herb that helps circulation
  • Garlic: Antiparasitic, immune booster, and insect repellent
  • Neem: Immune support and insect repellent
  • Wormwood: Antiparasitic
  • Black Walnut: Antiparasitic
  • Black seed: Antiparasitic

Holistic veterinarians may incorporate the following ingredients in their heartworm tincture:

  • Thyme: Supports immunity and repels mosquitoes
  • Peppermint: Insect repellent
  • Cinnamon: Heart health booster
  • Cloves: Antiparasitic

Another option is heartworm nosodes. A heartworm nosode is a homeopathic remedy prepared from a pathological specimen associated with heartworm disease caused by a parasitic worm called Dirofilaria immitis. The nosode is made by diluting and succussing (shaking) a sample of material containing heartworm antigens. In homeopathy, it is believed that such remedies, when highly diluted, can stimulate the body's healing mechanisms to address clinical signs associated with heartworm disease.

If you're looking for a natural preventative, talk to a holistic veterinarian or a canine herbalist about a tincture that's right for your dog.

Make Your Yard Unfriendly to Mosquitos

There are many natural ways to reduce the mosquito population in your yard, starting with removing all standing water. Mosquitoes breed in stagnant water, so eliminate any sources of standing water in your yard, such as birdbaths, clogged gutters, flower pots, and containers. Empty and clean these items regularly to prevent mosquito larvae from developing.

You can install mosquito dunks that contain a natural larvicide called Bacillus thuringiensis israelensis (BTI), which is harmless to humans, pets, and wildlife but kills mosquito larvae. Place dunks, such as ponds or rain barrels, where standing water cannot be eliminated.

Attracting natural predators of mosquitoes to your yard, such as birds, bats, dragonflies, and certain species of fish, by providing nesting sites, bat houses, and bird feeders will encourage natural predation of the mosquitoes. Some plants naturally repel mosquitoes, including citronella, lavender, marigolds, lemon balm, catnip, and basil. Plant these in your yard or pots around outdoor seating areas.

Keeping your lawn mowed short and removing overgrown vegetation where mosquitoes like to rest during the day prevents mosquitoes from breeding in your area. Trim shrubs and bushes regularly to reduce hiding spots.

You can limit outdoor activity during peak mosquito times. Mosquitoes are most active during dawn and dusk, so try to limit outdoor activities during these times. Create screened-in areas for outdoor seating or dining to protect from mosquitoes while you and your enjoy being outside. 

Keep Your Dog Healthy

Fleas and ticks do not thrive in the presence of a healthy dog. Begin your dog's path to better health before flea season arrives. To begin, make the following lifestyle changes:

Feed a fresh whole food diet, or add nutritious toppers to the kibble if you are not ready to switch to a completely fresh food diet.

  • Chemicals, pesticides, fertilizers, and hazardous cleansers should all be avoided.
  • Vaccines and pharmaceutical medications should be kept to a minimum.
  • Add finely chopped fresh organic garlic daily to your dog's meals. The medicinal benefits of garlic include antiparasitic properties.
  • Apply food-grade diatomaceous earth to your dog's fur from his ears to his tail.

Takeaway Bites

  • Toxins that kill fleas also negatively impact your dog.
  • There are natural alternatives for fleas, ticks, and heartworm prevention.
  • Utilizing a natural alternative can prevent the adverse effects often associated with pharmaceuticals.