Heartworm prevention began with diethylcarbamazine (DEC), approved by the FDA in 1977 and used daily, though it was introduced to veterinary markets in the 1960s; later, the more convenient monthly macrocyclic lactone preventives (like ivermectin) emerged in the mid-1980s, revolutionizing protection.

When did heartworm prevention start in dogs?

The first canine heartworm preventive medication, which contained diethylcarbamazine, was approved by the U.S. Food and Drug Administration (FDA) for daily administration in 1977.

What year did Heartgard come out?

Then came 1987, and the introduction of Heartgard, the first once-a-month heartworm pill. Life got even easier, for both veterinarians and dog owners.

How do dogs get heartworm naturally?

Dogs get heartworm naturally through the bite of an infected mosquito that carries immature heartworm larvae, which develop inside the mosquito after feeding on an infected animal (like another dog, coyote, or wolf). When the mosquito bites a dog, these infective larvae enter the bloodstream, mature into adults in the heart and lungs, and can live for years, reproducing and continuing the cycle. 

Is Heartgard just ivermectin?

Yes, Heartgard contains the active ingredient ivermectin (in combination with pyrantel in Heartgard Plus) and works as a monthly preventative for heartworm disease, as well as treating/controlling hookworms and roundworms in dogs and cats. The ivermectin kills heartworm larvae before they can mature, protecting against the disease, and the medication requires a veterinary prescription.

When to give your dog heart worm prevention

Which is safer, NexGard or Simparica?

Neither NexGard nor Simparica is definitively "safer"; both are effective, vet-recommended, FDA-approved monthly chewables, but they offer slightly different protections and have different active ingredients, with safety largely depending on your dog's individual health and lifestyle, so always consult your veterinarian for the best fit. Key differences include Simparica Trio's faster tick kill and Lyme disease transmission reduction versus NexGard Plus's broader hookworm coverage, while NexGard is suitable for younger puppies (8+ weeks) than Simparica (6+ months).

What is the controversy with Heartgard?

The Heartgard controversy centers on allegations that its maker, Merial, falsely advertised the drug as 100% effective, despite internal knowledge and FDA warnings (circa 2009) that its efficacy was closer to 95%, especially as heartworm resistance emerged; lawsuits claimed this deception led to dogs contracting heartworms, causing severe illness, while a whistleblower suit alleged cover-ups and improper data handling by Merial, though the company maintained product safety.
 

What temperature do mosquitoes get heartworms?

Maturation to the infective form inside mosquitoes requires approximately two weeks of temperatures consistently above 57 degrees Fahrenheit. When a mosquito harboring infective heartworm larvae bites another dog or cat, these larvae can be injected into that pet.

What months do dogs need heartworm pills?

Although there are fewer mosquitoes in the winter, there is still a risk that your pet could get heartworms if you stop giving heartworm prevention medication during this season. That's one reason veterinarians strongly recommend pets receive heartworm prevention medication year-round.

Can dogs survive without heartworm medicine?

Not all dogs with heartworm disease develop caval syndrome. However, if left untreated, heartworm disease will progress and damage the dog's heart, lungs, liver, and kidneys, eventually causing death.

What are the neurological side effects of Heartgard?

The following adverse reactions have been reported following the use of HEARTGARD Plus chews: depression/lethargy, vomiting, anorexia, diarrhea, mydriasis, ataxia, staggering, convulsions, and hypersalivation.

Why is ivermectin not safe for dogs?

In dogs who have the mutation, the drug crosses the blood-brain barrier and causes neurological damage, which can be lethal. Dogs can ingest ivermectin not only in the form of heartworm preventative, but also if they eat the manure of livestock that were treated with the drug for parasite control.

What is the best alternative to Heartgard for dogs?

10 Best Heartworm Medications for Dogs in 2025 [Vet-Recommended]

• Simparica Trio for Dogs.
• Heartgard Plus for Dogs.
• Interceptor Plus for Dogs.
• Credelio Quattro for Dogs.
• Revolution Topical Solution for Dogs.

What happens if you give a dog with heartworm a heartworm preventative?

Symptoms may not always be noticeable, but you don't want to start your pet on a medication if the heartworm is already in their system (it could be too shocking for their body and potentially be fatal). It's best to be safe and always check with your vet before starting any sort of medication.

What foods prevent heartworms in dogs?

Anecdotal evidence suggests that herbs such as garlic, black walnut and wormwood, and the homeopathic heartworm nosode, may actually prevent as well as treat infection.

What if I can't afford heartworm treatment for my dog?

If you can't afford heartworm treatment for your pet, here are some options to consider. You can contact local animal shelters or non-profit organizations that may offer financial assistance for veterinary care. Also, talk to your veterinarian about setting up a payment plan or negotiating the cost of treatment.

Are heartworms visible in dog poop?

Myth #3: If my pet has heartworms, I will see them in her feces. Although many worm types, such as roundworms and tiny hookworms, are shed in your pet's feces, heartworms do not live in the gastrointestinal (GI) tract, and are not found in feces.

What time of year is heartworm most common?

In most parts of the country, exposure risk is greatest during the warm months of summer and early fall.

What is the dog disease in 2025?

What are the causes of the dog virus outbreak in 2025? The 2025 dog flu outbreak is caused by highly contagious H3N8 and H3N2 influenza strains, spreading quickly in kennels, parks, and grooming facilities.

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