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Veterinary Clinic

A Heart to Heart on Protection from Heartworms

Picture have finally closed your eyes and gotten cozy to fall asleep nicely bundled in your blanket only to hear that all too familiar whine in your ear of easily the most sinister bug that ever existed....the mosquito. It wasn't enough that these little nuisances are fast, relentless bloodsuckers, but they actually deposit little presents as well. That's right, the gift that keeps on giving. Lucky for us, it's extremely rare to harvest these "gifts" in our bloodstream. Our 4-legged family members, though.......not so lucky.

As a client you most likely received our email with a link to see the video called Heartworm Basics from the American Heartworm Society. It is a fantastic synopsis about heartworm transmission and disease. To build off of that helpful information, how about some direction now on how to stop the spread of infection and disease in its tracks? In this article, I'm hoping to answer some questions about prevention and about treatment if we discover your pethas tested positive for heartworms

Deciding when to Start Prevention

When should I start my new puppy or kitten on prevention? The answer is as early as eligible, even as early as 4 weeks of age. At our office we usually start a puppy and kitten on the appropriate preventative (adjusted monthly by weight) until they reach an expected maintenance weight range before having the family purchase a 6-month supply. We recommend testing when the pet reaches 6-7 months of age. This is because testing at an earlier age may give us false information. Also, this helps us to decide if the prevention selected is the best long-term choice.

Deciding what Type to Use

With so many different types and brands of heartworm preventatives available, it can be a daunting task to decide which is best for your pet(s). Consider these questions when making a selection:

  • How old and how big is my pet now?

  • Is my pet a breed known to be sensitive to Ivermectin? (E.g. Collie)

  • With that info, are there some options my pet doesn't qualify for that I can cross off the selection list?

  • Does she have live adult fleas?

  • If so, will I plan to use a separate flea preventative that kills adult fleas?

  • If fleas are not a problem, do I at least want to use a flea regulator that prevents their eggs from maturing?

  • Does my pet have a food allergy, sensitive stomach, or resist oral medications?

  • Do my pets go to parks, boarding, training classes?

  • Do we travel with our pets?

  • Are they around outdoor animals (including stray cats)?

  • If so, should I consider other parasites they may be at risk for? (E.g. Hookworms, roundworms)

Though some of these questions don't exactly pertain to heartworms themselves, they definitely may help narrow down your choice of heartworm prevention.

Special Circumstances to also Consider

What if my pet is pregnant or nursing, should I still use preventative?

Absolutely, but there are some types that are labeled unsafe or have uncertain safety in such situations. For example, Trifexis and Advantage Multi have caution labels that suggest to avoid or to seek advice if pregnant or lactating.

What if my pet gets groomed but I want to use a topical, can I still apply one or should I choose a tablet instead?

Of the chart listed below, the only topical heartworm preventative that is not labeled as waterproof or water-resistant is Advantage Multi. If you choose this option, be sure not to bathe right away. In fact, labels for the other preventatives may suggest that you can bathe within 24 hours, but to get the best results, space out the bath by a few days when a topical is planned to be applied. Apply the topical ideally after this time post-bath instead of before the bath whenever possible.What if my pet has food allergies? If we know what the allergen is, we can easily avoid it. If we are not sure what your pet is allergic to, let's talk about the best option(s). It may be that a topical is the best plan, or that we use a tablet that avoids commonly known allergens.

What if I miss a dose by close to or more than 1 month?

Well, we are only human so this is bound to happen. When it does, let's talk about it. It may be that we will have your pet restart a preventative that would be safe in the event that she has contracted heartworms. Many preventatives can kill immature worms, but some could cause a severe reaction in their presence and cannot be given. It would be too early to test for heartworms if only 1 month was missed since it takes 6-7 months for the heartworm to mature to adulthood and be detected. So, the next step would be to test in 6 months to see how we are doing. If there is a possibility of missing multiple doses, retesting is recommended right away and a follow up test would also be planned 6 months later.

How often should we be testing?

The American Heartworm Society recommends annual testing for the detectable chemical (antigen) and for the larvae (microfilaria) for both dogs and cats.

For areas like ours where heartworms are endemic (regularly found in our area), we recommend testing every 6 months for a few very important reasons:

  1. Early stages of heartworm infection or low worm burdens may not turn up on the test. This could be because the worm(s) is immature and therefore not yet secreting antigen, or there is not a large enough number of worms to secrete enough antigen to be detected.

  2. As busy as we are, although dedicated to caring for our pets, we may get behind on our heartworm prevention.

  3. Our clever pets may be on to us and spit out (and possibly hide) their pill when we aren't watching.

  4. Differences in metabolism and immune response to parasites may make the preventative ineffective.

  5. The idea of the heartworm building resistance exists. We know that bacteria can build resistance to antibiotics. The survivors have characteristics that make their "offspring" warriors against medication. Some experts caution that heartworms may have similar mechanisms of survival.

Oh no! My pet has what?

  1. First, we need to verify with a second test (ideally different from the 1st) that there are indeed worms. This is important when considering whether to proceed with a vigorous treatment protocol.

  2. Then if confirmed that our patient is positive for presence of worms, we need to distinguish if we are dealing with heartworm infection or if there is actual heartworm disease. This involves looking at chest radiographs for heart and lung changes, doing an ocular (eye) exam, and checking baseline lab work to detect if other organs are involved due to traveling worms.

  3. If there are signs of disease, we will discuss the best steps to counteract the disease and work quickly to help prevent further damage. If disease isn't found, a slow and meticulous regimen is begun to best safely kill the worms.

  4. This involves using special medication to kill Wobachia, a parasite of the heartworm which is mostly responsible for the allergic reactions that occur as the heartworm is killed.

  5. It also involves strict rest, anti-imflammatories, and even a selective preventative that helps kill the heartworm larvae. It's very important that we discuss which one is used, because many are not safe inthe face of heartworms.

  6. The main effective weapon used to kill the heartworms is an injection called Immiticide. The American Heartworm Society recommends 3 injections strategically given after killing the Wobachia. The treatment is vigorous but effective, and with our careful technique, your pet can pull through this.

Taking action

Hopefully, this will equip you and prepare you for the task at hand.

The great news is there is so much we can do to prevent heartworm disease. Of course my team and I are here to help you and guide you through. From here, browse through the chart below of some of the most popular heartworm preventatives, their advantages and their limitations.

Then, call us for an appointment today to start protecting your beloved.

With Love,

- LaShonn McNair, DVM

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