What is the Best Heartworm Treatment for Dogs?

This isn’t going to be fair. It’s not a comparison of all the heartworm and flea medicines for dogs. You can find that by following the link (it even includes a handy chart).

Instead, when faced with such a large choice most people ask me what I think is best for their dog. That’s what this is.

These are my opinions and thoughts as an ‘older’ vet. I’m going to go through the bewildering array of products for dogs and pick out a few I think are outstanding. Although it definitely happens, I don’t receive any extra payments for selling certain products. I just want you to use something.

Why? Heartworm in Adelaide is under control now, but it wasn’t always so. The same is true for most of Australia, and we’re the lucky ones. I think that when you compare us to the rest of the world, we’ve done an excellent job of getting enough dogs on prevention.

So let’s get started. I’m going to use the pros and cons of Sentinel Spectrum as a guide.

What Is Sentinel Spectrum?

Sentinel Spectrum is a once-a-month flavoured tablet that prevents heartworm, fleas and intestinal worms in dogs. It is the most complete single product for these three groups of parasites. That’s why it’s deservedly popular. I like it too.


Once you understand it you might, like me, think there are better solutions. It’s a case of ‘jack of all trades, master of none’. I’m going to talk through each of the parasites in turn, plus a few extra it doesn’t cover.

Sentinel’s Flea Control

Sentinel contains lufenuron, an insect growth regulator. It kills fleas in the egg by blocking their growth. That’s great for safety. Being the only non-insecticidal product for dogs is certainly an excellent drawcard.

However, not killing fleas isn’t always compatible with the active lifestyle of most dogs. Your dog will undoubtedly pick up ‘travellers’ on the street, at the park, and even in your yard from stray cats. These fleas will live long, happy lives. So if you’re into flea welfare, Sentinel is the best. I have to admit I’m not a member of that group.

My Best Flea Control

Modern treatments in the isoxazoline class are very safe and extremely fast in removing fleas. Like Sentinel, they’re also tablets so you don’t have any messy drug and solvent on the coat.

There are three. Bravecto has taken a lot of heat for suspected adverse reactions in dogs, which I think is unfair. However, it’s still wise to avoid longer-acting products when shorter-acting products are effective. That’s because the initial dose is likely to be higher.

Nexgard I have no strong opinion of. Towards the end of the month, it’s a bit slower to kill fleas and ticks than the third product.

Simparica is my clear winner. I have seen no evidence of the other drugs out-performing it anywhere. Just yesterday I saw a dog that lives in the hills who has always had mite problems no matter what was used. Until this year, that is, thanks to Simparica. One very happy dog (and owner).

Hang on, did I just mention mites and ticks? That needs an explanation.

Is Sentinel a Mite & Tick Treatment?

Nope. Companies aren’t great at telling you what their products don’t cover. Here’s a list of the common mites and ticks of Aussie dogs, which is very similar to other countries.

  • Ear mites
  • Demodex mites
  • Sarcoptic (mange) mites
  • Paralysis tick (not present in Adelaide)
  • Brown dog tick

The paralysis tick deserves a special mention. At any one time, half of the patients in some vet hospitals in the eastern states can have tick paralysis. It kills without treatment and is very expensive to manage.

Now consider this: there’s a series of new products that finally are capable of preventing tick paralysis properly. I don’t blame those vets for being concerned about the financial impact on their practices. Those products are, once again, Simparica, Nexgard, Bravecto.

Why anyone living in a tick-prone area wouldn’t use these is a mystery to me. Even in boring old Adelaide, they will prevent all the mites in the list above, plus prevent paralysis ticks when travelling. I regularly see dogs on Sentinel who pick up ear mites, and Demodex is very common in puppies.

Sentinel’s Heartworm Control

Sentinel will kill heartworm larvae for one month after they are deposited by mosquitos. That’s the same as most heartworm preventatives on the market. Safe and effective.

However, if you read my history of heartworm in Adelaide you’ll see how we never had good control using monthly treatments alone. It’s not that they don’t work, it’s that we keep forgetting to give them. Me included. I used to remember it at 3 am and then forget it the next day.

My Best Heartworm Control

That’s why we recommend that most dogs receive the annual ProHeart injection, containing moxidectin. It doesn’t cost much more and works for 12 months after each dose in adults.

Hang on, I hear you say, didn’t you just tell me that shorter-acting is better than long-acting? Yes, that’s still true, and I certainly support the reliable use of any monthly treatment. The three reasons I think this is an exception are:

  1. Moxidectin is incredibly safe
  2. The dose is low as heartworm larvae are exquisitely sensitive
  3. Existing monthly treatments don’t work for most dog owners

Sentinel’s Intestinal Worm Control

Sentinel kills all the common intestinal worms in Adelaide dogs, including tapeworm. That makes it unique among heartworm treatments in 2018.

My concerns here are minor and easily ignored. I just don’t like worming dogs more than we need to. It’s a theoretical concern and there’s nothing to back up what I say. Except…

Studies in humans have shown the interesting link between allergy and being free of worms (reference below). It seems like the immune system needs something to keep it busy. In other words, it may be better that we pick up the odd worm than never have them at all.

My Best Worm Control

Existing recommendations to give a worming tablet every 3 months probably achieve a good balance. The life cycle for most worms is around two weeks. Dogs are likely to pick up worms at the park but never get enough to harm them.

When Sentinel Is Great

So now that I’ve picked on poor Sentinel Spectrum, let’s give it the chance to defend itself. It does a good job of heartworm and intestinal worm control if used correctly. It’s perfectly fine for fleas if dogs aren’t too social. Those fleas that are picked up won’t breed in the house.

It has one other distinct advantage that should not be ignored: price. For what it does, it stands out as the cheapest option. In a world where dog health depends on an owners’ financial state, this is also important.

So if you’ve chosen Sentinel, don’t feel that there’s anything wrong with that. I used it as an example but I could have done the same with most products. But I hope you can see how a tailored approach designed by your vet can be better.

Further Reading

Natural flea remedies | Australian flea & heartworm treatments

Feary J, Britton J, Leonardi-Bee J. Atopy and current intestinal parasite
infection: a systematic review and meta-analysis. Allergy.

Have something to add? Comments are welcome below and will appear within 24 hours of lodging.

By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. These blogs are from a series regularly posted on Facebook and Twitter. We do not accept payments or incentives in return for stories. Like or follow our page or subscribe via email to read the latest.


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