Heartworm medicine can add up to quite an expense each month- especially if you have multiple pets who need it.
As such, many owners wonder if it’s absolutely necessary to medicate their pets on such a strict schedule in order to prevent heartworm disease.
The crux of the matter is: Is heartworm medicine really necessary?
While some dissenting voices in the vet world believe holistic approaches or multi-month approaches are OK, the overall consensus is that it’s far safer to medicate your dog all year long.
That being said, it’s possible to medicate your dog or cat less than 12 times per year. For example, do so every three months or every other month and your pet may never succumb to full-on heartworm infestation.
In fact, while it is present in all 50 states, heartworm disease in the USA is still somewhat rare in certain areas. However keep in mind that, even with perfect blood testing, it’s impossible to know just how common heartworm is among wild dogs and other infected animals.
Additionally, we can’t overstate that outside contributors, such as weather, are largely beyond our control. As such, it’s possible – and even expected – to see heartworm disease cases spike during mosquito “booms” and low numbers during mosquito “busts.”
Finally, never forget that we can attribute lower numbers of heartworm cases nationwide to the vigilance of caring pet owners across the country. If every pet owner were to stop giving their pets heartworm prevention suddenly, the number of cases would predictably skyrocket.
So, is heartworm medicine really necessary? Science says yes, but in reality no one is forcing you to treat your dogs- so it’s up to you to draw your own conclusions from the facts that are available.
The good news is that skipping just one heartworm prevention dose is unlikely to cause lasting harm to your pet.
However, skipping doses regularly as you would on a tri-monthly or bi-monthly schedule does expose your pet to increased risk levels.
If you’re willing to take that risk in the name of saving money or other personal reasons, it’s up to you to decide if that is the right choice for you and your pet.
Many heartworm medications are designed to work with 15 extra days of “protection.” This means that even if you’re 15 days late, you can resume treating heartworm on your previous schedule.
If you miss more than 15 days, it’s best to adjust your pets to a new monthly schedule and administer a heartworm test to each pet at their next exam.
Some vets and pet owners argue that giving heartworm prevention every few months is enough to stave off the infection, especially in areas where cases are less common.
According to the American Heartworm Society, heartworm larvae can take as little as 51 days to reach their juvenile and adult worm stages.
Monthly heartworm prevention is not actually a real “preventative”; rather than killing and repelling the heartworm parasite throughout the month, it only kills the larvae present in your pet when you administer a dose.
As such, even if you give the medicine to your dog or cat every other month, the larvae could still mature within that 51-day window if your pet becomes infected shortly after receiving their monthly preventative dose.
The chances of this happening are much lower in colder states with a lower prevalence of mosquitoes, but the risk factors are still there. It’s up to you to determine for yourself, based on these factors and others, “Is heartworm medicine really necessary for my pet?”
There’s a reason why vets won’t prescribe your dog more heartworm prevention medicine until they’ve had a thorough exam.
Not only is heartworm medicine ineffective on heartworms that have grown past the larval stage, but giving heartworm prevention to a pet with an active infestation can cause serious side effects and health risks.
Once the adult heartworm matures and begins to reproduce within the body, it will release microfilaria (baby heartworms) into your pet’s bloodstream.
The heartworm prevention you administer each month will kill these baby worms, but this treatment can cause adverse effects in the process.
For example, dead microfilaria in your dog or cat’s bloodstream can become the source of a blood clot under certain conditions, which can be deadly for your pet- especially those that are older or already unwell.
The FDA and AHS recommend that your pet receives heartworm prevention once per month.
In fact, the AHS has come up with the clever lingo “Think 12” to help you remember to give a heartworm test every 12 months, and 12 heartworm prevention doses per year.
Note that there are heartworm medicines that last longer, though – some injections can last as long as a year before you’ll need to medicate again.
As we summarized above, whether you adhere to that guideline is entirely up to you and your vet. Monthly prevention is the only way to guarantee that your dog will remain heartworm-free.
Still, if you live in an area with a lower infection prevalence, you may decide that medicating your dog less frequently is an acceptable risk.
Is heartworm medicine really necessary in the winter?
According to the AHS, the answer is yes, but the final decision is up to you. Many factors come into play to determine your pet’s risk level, including the severity of the mosquito season, animal migrations, natural disasters, and much more.
For example, according to the AHS, after Hurricane Katrina in 2005 more than a quarter of a million homeless pets were relocated after the disaster- many of which had heartworm disease.
Patterns and anomalies like this alike contribute to the spread of the disease throughout the world each year.
It’s also been documented that many species of mosquitoes can survive throughout the winter indoors, passing infectious diseases onto their offspring next year. Heartworm cases have also been reported in Alaska, despite its low temperatures for much of the year.
While it’s true that your dog or cat’s risk of developing heartworm is lower during winter, it isn’t nonexistent. For example, if you travel with your dog during the winter months, you’ll need to consider heartworm risk factors for the areas you travel through.
It takes just one mosquito bite for your pet to become infected, after all.
While we all want to avoid as many strong, harsh chemicals as possible (and the dangers that may be involved), it may not be a good idea to skip the medication when it comes to heartworms.
While you may see many supposed home remedies for heartworm treatment around the internet, the only truly effective option in this situation is prescription medicine. So-called “natural” heartworm prevention just isn’t going to give your dog the protection it needs.
There are natural methods that you can use to lower the risk of your dog developing heartworm disease, however these are generally not sufficiently effective to be able to make forgoing prescribed heartworm preventatives a good decision.
Heartworms are transmitted through infected mosquito bites, so one of the most natural, logical ways of preventing heartworms is by reducing mosquito contact around your dog.
There are many home remedies out there that can help to make your dog a less attractive target for mosquitos, such as using certain essential oils or repellents.
However, while repellents do discourage mosquitoes from biting, they don’t prevent all possible incidents of bites. Some mosquitoes may be less affected by certain repellents (or may just be super-hungry), and all it takes for heartworms to develop is one single bite.
Another common ‘natural’ way of heartworm prevention commonly touted by holistic vets focuses on building up the immune system of the dog.
The theory behind this is that if the immune system is strong enough, it will be able to fight off foreign invaders such as a heartworm infection.
While it is always worthwhile to improve the health of your dog through positive dietary and exercise changes, there is no evidence that doing so will specifically help to prevent heartworms from developing.
No vitamins or supplements are capable of preventing or killing the parasites.
In any case, though it may be hard to believe at first, many heartworm preventatives such as Heartgard and Interceptor are actually derived from nature!
For example, ivermectin, the active ingredient in Heartgard, is a compound that comes from the natural fermentation processes of organisms that inhabit dirt.
Therefore, while its effects might be powerful as a medicine, heartworm preventatives may also be more ‘natural’ than you think!
To answer the question, “Is heartworm medicine really necessary?”, it really comes down to your personal preferences, situation, and risk assessment as a dog owner.
While it is generally agreed upon by vets and the AHS that heartworm medicine is the only way to guarantee prevention of heartworm disease, it may be possible to give it to your dog less regularly than once per month.
This is due to the fact that many heartworm medications have a 45-day effectiveness period.
Heartworm medicine may also not be as vital in cooler climates where there are less mosquitoes- though again this is no guarantee since places as cold as Alaska can be home to the little bloodsuckers!
Finally, if you are weighing up the benefits and risks of supposed home remedies or repellents as an alternative form of heartworm prevention, understand that those forms of protection are far from proven or effective.
While it’s always a good idea to boost your dog’s immune system and to keep mosquitos away from your pup, at the end of the day the only truly scientifically-proven method of preventing heartworms is through the use of medicines such as Heartgard or Sentinel.
Heather Abraham is an owner of two dogs, one cat, a leopard gecko, and a parrot (who her dad still cannot teach bad words to), and an avid blogger. From the time she was a young girl, she always felt a connection with pets. She brings her love of every type of pet to you, with information on animal nutrition, medication, toys, beds, and everything else in between. Along with newly-on-board veterinarian DVM editor Elena, she puts pups first while offering other various fun tidbits along the way.