What’s the Best Heartworm Prevention for Your Pet?

//What’s the Best Heartworm Prevention for Your Pet?

What’s the Best Heartworm Prevention for Your Pet?

Heartworms are parasites that often take up residence in the heart and lungs, resulting in severe lung disease, heart failure, organ damage and death. While the dog is the host-of-choice, they are also known to infect cats, ferrets and, in rare cases, humans.
dog and cat

Where do heartworms come from?

That’s an easy one – mosquitos!
In many areas of the United States mosquitoes are a huge problem. They a) are very annoying and b) transmit diseases to both humans and pets through their bite. Local governments have been know to spend thousands of dollars attempting to control mosquito populations.
When a mosquito bites any heartworm-positive animal, it picks up microscopic baby worms, called micorfilaria, which develop and mature inside the mosquito. Then, when the infected mosquito bites another dog, cat, or whatever, the larvae enter the new host through the mosquito’s bite wound.

How can I tell if my pet has heartworms?

Many dogs, especially those with sedentary lifestyles, will show little or no sign of infection even after the worms become adults. In fact, even a blood test will not detect heartworms in the earliest stages.
However, active dogs and those with more advanced infections may show the classic signs of heartworm disease, including a cough and fatigue after exercising. As the heartworms build up in the arteries, it can cause weight loss, fainting, coughing up blood and, finally, congestive heart failure.
Cats are not a natural host for heartworms, so the majority of heartworm larvae do not survive in cats. But, unlike dogs that show few symptoms, just a few adult heartworms can result in loss of appetite, difficulty breathing, and even shock, fainting or sudden death!
Once a dog or cat is diagnosed with heartworm disease, some of the damage may be irreversible. Depending on the severity of the infection, treatment options can be incredibly stressful, sometimes requiring surgery.
The disease is much easier to prevent than to treat, therefore heartworm prevention is vital!

What’s the best heartworm prevention?

Short answer? It depends.
Which monthly heartworm prevention product you choose should be based on your (and your pet’s) specific needs and concerns.
To get started, grab a pen and paper and jot down the answers to these questions:

  • How much can you afford to spend on heartworm medication?
  • Does your pet have allergies? If so, what ingredients do you need to avoid?
  • Are you able to administer the heartworm medication? on a regular schedule?
  • Is your pet at risk for exposure to other parasites?

Got your notes? OK. Let’s compare the 3 main types of heartworm medications available on the market.

Oral Medications

Oral tablets are by far the easiest for most pet owners to administer.
When it comes to any oral medication, never underestimate the power of a good bribe. Wrapping the medication in a ball of something super-tasty, like wet food or cheese, will encourage them to gulp it down without checking it out too closely.
Some of the more popular oral heartworm medications include:

Heartgard Plus

Available for dogs and cats.

  • Cost: $$
  • Main ingredient: Ivermectin and Pyrantel pamoate
  • Treats: heartworms, roundworms and hookworms.
  • Dosage: monthly

Heartgard Plusis very popular with its unique beef-flavored chewable cube. The flavor makes it very easy to give to your pets – they think they’re getting a treat!
I’ve seen a few places that warn against Heartgard for herding breeds, like collies and shepherds, because they have a genetic sensitivity to ivermectin. While that is true (the sensitivity is associated with a deletion mutation of the mdr1 gene), it takes a relatively high dose, like one used to treat mange, to stimulate a reaction. The dose in Heartgard is too low to cause a reaction and is safe for all breeds.


Available for dogs and cats.

  • Cost: $$
  • Main ingredient: Milbemycin oxime
  • Treats: heartworms, hookworms, roundworms and whipworms
  • Dosage: monthly

Interceptor is a small, chewable pill that is very palatable. Some people even say that their pets like the taste! If you have a pet that may have gotten wise to the game (no more hiding medicine in food) this could be something to try.


  • Cost: $
  • Main ingredient: Ivermectin and Pyrantel pamoate
  • Treats: heartworms, hookworms, roundworms and whipworms
  • Dosage: monthly

Tri-Heart is a less expensive, generic form of Heartgard Plus. It has the same ingredients, so is a great option if you’re on a budget.


  • Cost: $$$
  • Main ingredients: spinosad and milbemycin oxime
  • Treats: heartworms, hookworms, roundworms, whipworms and fleas
  • Dosage: monthly

Trifexis is unique among oral treatments because it prevents heartworms and fleas, which is very convenient for pet owners. These drugs are potent — they have to be to kill these awful parasites! — so many dogs experience an upset stomach after taking the pill.

Topical Liquids:

The biggest complaint I hear about liquid heartworm prevention is how messy it can be – especially if your pet is a wiggler! I always recommend a YouTube search if it’s your first time. There are several great how-to videos out there, including this one from Southampton Pet Hospital.
Some of the more popular topical heartworm medications include:

Advantage Multi

Available for dogs and cats.

  • Cost: $$$
  • Main ingredient: Moxidectin and Imidacloprid
  • Treats: heartworms, hookworms, roundworms, hookworms, whipworms and fleas
  • Dosage: monthly

Advantage Multi is great in that it controls multiple internal and external parasites, eliminating the need to give your pet multiple medications. On rare occasions I’ve seen irritation and sensitivity at the application site, and, even more rare, neurological reactions in hypersensitive pets. It’s also pretty expensive, so first time users are best off purchasing a small supply to see how their pet reacts. If it works well, you can find lots of coupons and discounts for larger quantities.


Available for dogs and cats.

  • Cost: $$
  • Main ingredient: Selamectin
  • Treats: heartworms, fleas, ticks, scabies, and ear mites
  • Dosage: monthly

This is often the first heartworm preventative that I will recommend for cats, especially given its other benefits. While it is also good for dogs, it has to be diligently applied (no missed doses!), so it’s a good idea to combine this with an oral heartworm prevention medication like Heartgard or Interceptor. I have occasionally seen mild stomach upset and temporary hair loss at the site of application in cats.


Can’t commit to a monthly dose? Well maybe an injectable heartworm medication is for you. The only injectable heartworm medication currently on the market is ProHeart.


  • Cost: $$
  • Main ingredient: Moxidectin
  • Treats: heartworms and hookworms
  • Dosage: 6 months

ProHeart is is very convenient for pet owners have trouble with a monthly dosage schedule. Unfortunately, Proheart is not the best choice for all dogs, especially those who are old or may have an allergy to the ingredients. Your veterinarian can determine if your dog is a good candidate.

Please note: All pets should be tested for heartworms before starting any preventive program. Talk to your vet with any questions you may have about heartworm prevention.

How can Activ4Pets help?

The huge problem with preventing heartworms is compliance. It is very common for dogs to be off heartworm prevention for significant amounts of time during their life. People either forget to give the pill each month, run out of pills, or have busy schedules and just put it out of mind.
With Activ4Pets you can set reminders making it easy to keep track of all your pet’s medicine, especially your heartworm prevention of choice.
Ready to get started? Sign up for Activ4Pets >>
Activ4Pets has monthly reminders so your pet will never miss a dose

Meet the Author


Dr. Clayton Jones

Dr. Jones has 25 years of veterinary medical experience as a staff veterinarian and medical director of his own practice. He also is a member of the American Veterinary Medical Society and President of the US-Cuba Veterinary Cooperation Society.

By | 2018-08-08T21:14:35+00:00 April 4th, 2016|Blog|1 Comment

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