Help Your Pets Fight Heartworm Safely

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Help Your Pets Fight Heartworm Safely
By Steve Brown and Beth Taylor


Minimizing toxins is one of the foundations of our "Live Longer" program in which we use only those medications, preventatives and treatments that are most useful and necessary. With careful evaluation, some "approved toxins" may be avoided. Medications are by their nature toxic to certain organisms, and often have serious short- or long-term side effects for our pets.

That said, sometimes chemicals are necessary to save lives. The chemicals used to prevent heartworm are extremely effective and can save dogs from difficult, unpleasant and potentially dangerous treatment. However, many veterinarians recommend treatment schedules which result in far greater quantities of toxic chemicals being ingested by dogs than is really necessary or even advised by the American Heartworm Society (AHS).

Consider these easy steps you can follow to minimize the amount of medication you give your pets.

The Heartworm Season Varies By Climate

The transmissibility season for heartworm is determined by temperature. In order for the larvae of the heartworm, carried by mosquitoes, to be transmitted to a dog, the temperature must be at least 60 degrees for a month.

For example, the heartworm season in Florida will be quite long. In fact, it might make sense to give preventative treatments year-round there.

In Chicago, however, the temperature necessary for transmission of heartworm is not usually reached at night until June. The beginning of the season is not likely to be earlier than June 1 in most years, and perhaps later, even though mosquitoes may be present. Temperatures begin to drop at night by September. And, the season will certainly be over the next month, although you may still see mosquitoes.

Preventatives Kill Heartworm Larvae

The chemicals used to control heartworm are called preventatives, but when we use them, we are actually treating larvae. Think of it this way: The chemicals kill the larvae your dog may have picked up in the period since the last dosage.

The drugs you can use include daily doses of Diethylcarbamazine Citrate (DEC) or monthly doses of Ivermectin (Heartgard or Iverheart), Milbemycin (Interceptor) or and Selamectin (Revolution). A six-month treatment (Proheart) was pulled from the market last year after numerous adverse effects, including deaths, were reported.

The daily preventative (DEC) is not easy to find since the introduction of Ivermectin and other monthly treatments. Nevertheless, it is quite effective and many feel that it is easier on their bodies. However, if DEC is given to a dog that is already heartworm-positive, anaphylactic shock may result. That's why completing a heartworm test prior to giving any medication is imperative.

There are two other issues that motivate us to keep using "monthly" preventatives versus daily medication.

For one, some dogs stash pills away in their mouths and dispose of them where you can't see them. Be sure the dog is swallowing them (as we learned when Steve discovered a cache of pills behind a chair). Heartworm medication must be swallowed to be effective! Fortunately, Steve's dog, Garbo, didn't contract heartworm.

The other drawback to daily preventatives is humans must remember to give them! Missing doses may result in infections. This is how two of our dogs contracted heartworm. While May survived the arduous treatment, her brother was blinded. Too bewildered to make the adjustment, he was soon euthanized.

Though that was long ago, treatment protocols have improved vastly, but can still be very toxic to your animals. We prefer providing regular oral preventative medication to the harsh reality of treating a heartworm-positive dog.

Monthly treatments are best kept as simple as possible. There are a number of options based on several chemicals. You have a choice of a pill (flavored or unflavored) or a topical treatment. And some are "multi-purpose" drugs.

We prefer dogs only receive medication that specifically prevents heartworm, rather than a silver bullet that treats everything. Some manufacturers formulate products that combine heartworm prevention with worming medication, flea, tick and mange medication, just in case your dog may encounter these parasites.

In our minds, that just-in-case scenario is not good enough to put a multitude of toxic chemicals into your dog's body. Plain Ivermectin (Heartguard) is the simplest choice, and the safest for most dogs, though certain breeds have shown some sensitivity to it. We recommend you discuss the least toxic options for your pet with your holistic veterinarian.

And, keep an eye on your dog for a while afterward to ensure your dog swallows her pill too! While it doesn't happen often, dogs occasionally vomit these pills.

When to Start and End Medication

To determine the best time to test for heartworm, read the guidelines posted on the AHS Web site. Each geographic area is different.

So, you've had your dog tested this spring, and she's clear of heartworms. How do you know when to start the preventative?

Heartworm is not transmissible from mosquitoes to dogs until the weather is quite settled and warm, and the medications work on larvae acquired after the season starts. The time to start recommended by the AHS is a month after the transmissibility season begins.

The chemicals used for monthly prophylaxis are effective for at least six weeks.

Many treatment protocols recommend one-month intervals year-round to account for missed doses and client (that's us!) unreliability. The concern of veterinarians that administration will be incomplete is certainly valid, because humans may fail to give sufficient attention to the right dates. However, it's easy enough to mark them on your calendar medication to save your dogs unnecessary chemical exposure.

Holistic veterinarians often recommend the first dose be given a month after the season begins (dealing with any larva which may have been acquired and allowing for a little overlap) and every six weeks after that, until the end of the season. The AHS recommends the last dose be given within a month after the season ends.

How many doses will your dog need? In a normal Chicago climate, four would do the trick (July 1 Aug. 15, Oct. 1 and Nov. 15). Even if you are extra conservative, no more than one more dose will be needed. If you start May 15, you'll end Oct. 1. Few Octobers in Chicago have nights above 64 degrees, but if this occurs, one more dose would be needed before the end of the season. Close attention to the weather, particularly night temperatures, will give you excellent information about when to start.

Protecting The Liver

Some concerned dog caretakers have sought out more holistic, natural options such as herbal or homeopathic remedies. If you don't want to use traditional heartworm medications, it's imperative your animals be under the care and supervision of a veterinarian with expertise in this area.

Holistic veterinarians often recommend herbal support for the liver following treatment. Chicago area holistic veterinarian Karen Shaw Becker suggests a daily dose of milk thistle for the week following each treatment. Milk thistle supports the liver as it metabolizes the medication and aids in the body's detoxification processes.

Our main goal is to minimize our animal's exposure to chemicals, including those used to prevent heartworm. We recommend supplying the smallest amount of drug that will do the job, for the shortest time period to be effective. This balance provides the best solution to a major health threat, with the minimum amount of medication, followed by appropriate detoxification.

Of course, the support of a whole food diet and an active and stimulating life will also help your dogs live long healthy lives too!

What About Cats?

In the past few years, veterinarians have begun to recommend that cats receive chemical preventatives for heartworm. This article is addresses heartworm prevention for dogs only. Cats are not the natural hosts of heartworm. In fact, the incidence of feline heartworm causing clinical disease is very low compared to dogs.

Still, bear in mind the actual risk your cat will encounter mosquitoes when making a decision about medication.