- What Are Heartworms And Why Are They Dangerous?
- The Potential Risks of Heartworm Medication
- Common Side Effects Of Heartworm Medication
- The Best Heartworm Treatments
- In Summary
Every dog owner needs to understand the threat of heartworm disease in dogs, and at the same time be aware of the various dangers of heartworm medication and treatment.
For those among us that are uninitiated, you may ask, “But aren’t heartworms just, you know, worms? How much damage could little squiggly things do, really?”
You’re in for a treat.
Sometimes, people think that because their dogs live predominantly indoors that they don’t need to worry about heartworms.
Unfortunately, that just isn’t true.
As the name implies, heartworms are parasitic worms that invade your pet’s bloodstream and take over the heart and surrounding tissue.
These worms enter the bloodstream through mosquito bites. They start as parasites- small larvae that will settle into the heart muscle and grow into worms. These worms can be anywhere from 8 to 14 inches in length.
Unfortunately, they don’t just stay in the heart. If the infection is bad enough, these worms can invade the surrounding blood vessels. Furthermore, they can make their way into a dog’s lungs and take root there as well.
Before the late 1960s, the only regions in the United States afflicted with this specific worm (a parasitic nematode) were the eastern coastal states and the south. Unfortunately, it has managed to spread to not just the 48 contiguous states but even Alaska and Hawaii.
While your pet is most likely to get infected during the summertime months when mosquitoes are most active, parts of the country that experience mosquitoes during all seasons still need to be cautious as they are always at risk.
Firstly, you need to understand that the heartworms can cause life-threatening damage and will kill your pet if left untreated. If your vet tells you that your canine has heartworms, your only true option is treatment.
As the parasites grow from larvae to mature worms, they will slowly begin to inflict damage to the heart and make it difficult for it to function. If they have spread to the lungs, these worms will also decrease your pet’s lung function.
When the worms impede heart function, they will eventually impact every other organ. The rest of your dog’s body won’t get the blood and oxygen it needs to thrive, which can cause the immune system and most vital organs (the kidneys, liver, and lungs) all to fail.
These worms work their way out of your dog’s system on their own. Treatment is the only option once your pet is infected.
The most expensive solution is also one of the safest: having a boarded cardiologist surgically remove the worms in a minimally invasive procedure. That may sound like good news, but it’s often out of most pet owners’ price ranges.
The other treatment options, which will be discussed later, are also expensive and, worse, dangerous.
One of the worst aspects of heartworms is that there may be no signs until it is too late, which is why it’s vital to get your pets tested at the very least once a year. Doing so can allow you to catch heartworms before they become fully grown.
Getting a handle on treatment early on can save your dog much suffering. If you can kill the heartworms before they grow large, your pet’s organs won’t suffer the same kind of damage that they will from fully-formed worms.
However, there are some symptoms you should keep an eye out for, just in case.
For instance, if you notice that your dog is tiring much more than usual when out and active, you may want to consider getting them tested. Sudden exhaustion can be a sign that their heart is straining, impacted by the worms.
Similarly, your dog may develop a regular, deep cough, especially noticeable when active. Such a cough is both a sign of heart and lung difficulty, so it’s imperative to get your pet tested, especially if combined with unusual exhaustion.
Untreated, this can lead to your dog losing weight and struggling to breathe or breathing rapidly. Your pet may begin to faint periodically. If you notice any of these signs, you must get your canine tested right away.
Heartworm medication can be both painful and dangerous for your dog. However, leaving your beloved companion untreated is a much more painful and often deadly option.
As we’ve discussed, if your dog tests positive for heartworms, the only option available is a treatment for the condition.
Regrettably, that doesn’t mean the treatment itself is without risks. Once the infection has occurred, and treatment has begun, your canine will still be in jeopardy. However, the dangers of heartworm medication are worth it to save your pet.
There’s no easy answer to identifying the safest medications for your dog. Some treatments are arsenic-based, which is a danger in and of itself. Overtime, arsenic can cause lesions and dramatic weight loss.
Arsenic-based treatments kill the worms effectively, but their bodies remain in the heart muscle.
As they break down, large numbers of heartworm fragments may enter the bloodstream, blocking vessels. Their bodies can act in a similar fashion as living worms, preventing blood and oxygen from reaching vital organs, such as the kidneys and liver.
If your pet is showing signs of heavy distress, your vet may have to stabilize your dog’s condition before treatment can be administered. Such care can include a number of medications as well as fluid therapy.
The most common treatment, and the only adulticidal approved by the FDA as of 2014, is Melarsomine dihydrochloride, an arsenical therapy. It is administered in three stages, one via deep intramuscular injection, and then a month later, two more injections spaced out by 24 hours.
Again, exercise must be curtailed for the safety of your dog and not just because the breaking-down bodies of the worms can block arteries, but also because they may break down in the lungs as well. Rest is vital to prevent blood vessels from rupturing.
Even worse, this treatment may only impact the adult worms, so those in the juvenile stage may remain unaffected.
Because of this, your vet may prescribe your pet another medicine, doxycycline, for at least a month. Doxycycline will help to prevent larvae from growing and becoming a new infection later on.
If the case is severe enough, the only option may be surgical extraction, which, as we’ve mentioned, is even more expensive.
Your vet may suggest surgery when what is called caval syndrome has developed, which is scientifically known as diroliarial hemoglobinuria.
This means that the worms are so numerous that the heart’s valves cannot close, which typically results in the death of the pet within a handful of days.
Within a few weeks of a successful surgery, the dog must go through the arsenic treatment once they have recovered to ensure no lingering worms mature.
While the dog is recovering from this treatment, owners must keep their pets as relaxed as possible, with no excess physical activity. They will often feel fatigued, and may even have a fever or cough.
There are different treatment options once your pet has contracted heartworms, but they are all expensive and can put your dog at risk. While heartworm treatment is vital to save your pet’s life, the treatment itself can be dangerous.
The answer to this question may not please you. According to a study done by Louisiana State University, about fourteen percent of dogs pass away during treatment for heartworms. That’s one of the reasons why prevention is key.
Certain dogs have a genetic mutation that makes them sensitive to ivermectin, which is a common ingredient in heartworm preventative medication.
Sensitivity may cause an extreme reaction in some dogs. It’s known as ivermectin toxicity and can be so severe that it could endanger a dog’s life.
The sensitivity itself is a product of a mutation of the MDR1 gene. That mutation means the medication breaks through the blood-brain barrier, which protects against pathogens or toxins. Due to that, the medication could cause serious neurological issues for some dogs.
Some dog breeds are more vulnerable to having the mutation than others.
Specifically, herding breeds like the Australian Shepherd and Border Collie, as well as sighthound and herding breed mixes will be especially vulnerable.
In fact, studies have indicated that the highest frequency of mutation is amongst Collies, with upwards of seventy percent affected.
Symptoms range in severity, from the mildest effects to more acute manifestations. When there is an acute reaction to monthly preventative medication, the symptoms will likely start displaying within four to 12 hours. Milder symptoms take up to three days before they become noticeable.
The signs vary by individual dog, but it’s still good to know what to look out for.
They include lethargy, a loss of appetite, trembling, slowed heartbeat, and difficulty breathing.
Other symptoms might be more extreme, such as seizures or sudden onset of blindness. Extreme cases may result in a dog becoming comatose or requiring ventilator-assistance to breathe.
Thankfully, dogs can be checked for the mutation in a few different ways.
The genetic test involves a cheek swab kit that uses a small brush to swipe the dog’s mouth. There is also an EDTA whole blood test. Owners can request a test kit from Washington State University’s Veterinary Clinical Pharmacology Laboratory.
Alternatively, an owner can request a vet to perform the test and submit any samples themselves.
The best heartworm treatment is prevention.
If you can stop your dog from contracting heartworms from the get-go, you’re giving them their best chance to enjoy a long and healthy life, especially considering the dangers of heartworm medication.
Thankfully, there are steps you can take to prevent your pet from being infected. However, even if you follow the plan laid out by your vet perfectly, you will still need to do yearly testing, as no prevention is perfect.
According to the FDA, the “best treatment is prevention” to avoid the dangers of heartworm medication.
Your vet will need to prescribe preventative treatment.
Typically, these treatments are given monthly in the form of a tablet or a topical liquid you’ll have to apply directly to your dog’s skin.
You can get a chewable or non-chewable tablet, depending on what’s easier for your canine. There is also a semi-annual injection that a vet can give your pet to keep them safe.
Best of all, these products will frequently protect your dog against other parasites, like intestinal worms (roundworms or hookworms), ear mites, fleas, and even ticks.
The American Heartworm Society suggests that dog owners keep the phrase “think twelve” in mind when it comes to heartworm. Think twelve means that prevention should happen twelve months of the year, and testing should happen once every twelve months.
They also suggest making sure that any parasite prevention you’re giving your dog includes heartworms specifically. For example, giving your dog tick and flea medicine is not enough to protect them from becoming infected with heartworms.
It’s wise to really keep your preventative treatment going twelve months of the year. Even if you think the mosquitoes in your area are dormant, it’s best to take every precaution possible, considering how dangerous and deadly heartworms can be.
It is also vital to maintain the preventative medication schedule accurately. If you miss a day or two, you may be leaving your dog vulnerable to infection. Always be sure to discuss the medication and scheduling with your pet’s vet if you have any questions or concerns.
As already discussed, the safest and most inexpensive way to deal with heartworm is to prevent it in the first place.
While you could keep your best pal inside to protect them from it, that is neither practical nor beneficial for your dog’ health. Even keeping your yard relatively safe from mosquitoes, such as by eliminating any standing water or spraying regularly, may not be enough.
Preventive medicine is, therefore, the best bet when it comes to dealing with heartworm. These medications act against larvae that have inhabited a dog for between one and two months.
If they have been a host for heartworms longer than that, then preventive medication may not be sufficient.
Owners have a number of safe options available to them, including oral delivery of preventive medication, a topical liquid, and an injectable.
An injection can offer six months of protection with a single shot. ProHeart 6 is delivered subcutaneously, but it’s important to consider the potential risk of anaphylaxis if your dog has preexisting allergies or is otherwise sick or dealing with weight loss.
Typically, oral treatments are safe for healthy dogs, but it’s always important to speak to your vet about any concerns.
Common monthly oral treatments include Heartgard Plus, which contains ivermectin and pyrantel, and Sentinel, which uses milbemycin oxime and lufenuron.
Each protects against heartworm, as well as infestations like roundworm and hookworm. Sentinel can also prevent flea egg maturation.
Advantage Multi is a topical medication that protects against other infestations, such as fleas, roundworm, and mites. Revolution is another topical treatment that protects against mites and some ticks.
Generally, veterinarians strongly recommend that preventive medication be an all-year treatment.
As you have no doubt learnt from this article, heartworm disease is not something to be trifled with.
Not only are the worms themselves capable of causing great damage inside a dog’s body, but once infestation has taken place the medication and treatment used to combat them can be very dangerous themselves.
Treatments commonly involve the use of arsenic-based drugs and surgery, with all their associated negative side effects.
Further to the bombardment of chemicals, treatment for mature heartworms is so taxing that dogs have to be kept as sedentary as possible in the weeks that follow to ensure that blood vessels do not rupture.
Yet, despite the considerable effort expended to kill the heartworms, 14% of all dogs treated do not survive the procedure due to various complications.
Therefore, it is abundantly clear that prevention is the true key to keeping your dog healthy and away from the dangers of harsh heartworm medication and treatment.
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.