Heartworm disease (dirofilariasis) is a serious and potentially fatal canine disease in the United States. It is caused by long worms (about a foot long) that live in the heart, lungs, and associated blood vessels of an affected dog.
What Are Heartworms?
Heartworms live in mammal species, such as dogs, cats, ferrets as well as wild animals such as foxes and coyotes. Wild animals are considered an important carrier of the disease.
Canines are a natural host for heartworms, which means the heartworms can live inside a dog, lay their eggs, and reproduce. If untreated, dogs have been known to harbor several hundred worms in their bodies.
Heartworm disease can cause lasting damage to the heart, lungs, and arteries of affected dogs, and reduce the quality of life for a dog long after the parasite is gone. For this reason, prevention is by far the best option and treatment should be administered as early as possible.
How Do Dogs Get Heartworms?
The only way a dog can get heartworms is through a mosquito bite. There’s no way to tell if a mosquito is infected or not, which is why prevention is so important.
Heartworm disease has been reported in all 50 states; it only takes one bite for your dog to get infected.
It takes about seven months from the time a dog is bitten by an infected mosquito for the larvae to mature into adult heartworms. At that point, the heartworms crawl into the heart, lungs and blood vessels of the infected animal and begin reproducing. Adult heartworms are 12 inches in length and can live 5-7 years and a dog can have as many as 250 worms in its system.
Can Dogs Pass Heartworms to People?
It is exceedingly rare for an animal to pass heartworms to human. This is because heartworms can only be passed on by mosquitoes. Heartworms are a specific parasite that generally only affects dogs, cats, ferrets, and wild mammals. In rare cases heartworms have infected people, but they don’t complete their life cycle in humans.
By the same token, heartworms are not passed between pets in the same household. This is because heartworms are transmitted through the bit of an infected mosquito.
What Are the Symptoms of Heartworms in Dogs?
Initially, there are no symptoms. But as more and more worms develop in the heart and lungs, your dog will develop a cough. As it progresses, they won’t be able to exercise as much as they used to and they will become tired more quickly. Once the disease becomes severe your dog can pass out from the loss of blood to the brain and is likely to retain fluids. Most dogs will eventually die if not treated.
Why You Should Ask Your Vet for Prescription Heartworm Prevention Medication
Before you administer heartworm prevention medication, you should have your dog tested to ensure he or she does not have an active infection before giving preventative medication. If, for any reason, your dog is already infected, it could be dangerous to give your dog medication. Prevention medication only is effective on early stage larvae and microfilariae (earliest life stage that circulates in a dog’s blood).
There are various types of prevention medication combinations effective against heartworms and other parasites, such as mites, ticks, roundworms, hookworms, whipworms and fleas. Your vet will prescribe the right prescription for your dog based on geography and your dog’s individual needs.
Read more: What Every Dog Owner Should Know About Worms in Dogs
What Is the Treatment for Heartworms in Dogs?
There are a few treatment options. All treatments today come in the form of an injectable.
If heartworms are suspected in your dog, your veterinarian will order an extensive pre-treatment workup, including x-rays, blood work and tests to determine how far the disease has progressed in your dog. Once your dog is diagnosed your dog will be prescribed injections. Your dog will need to be kept quiet for several months during the treatment period.
It’s important to note your dog won’t “outgrow” heartworms; if your dog is infected, he or she stands a good chance of dying from the disease.
How Much Does Heartworm Diagnosis and Treatment Cost?
The average cost for prep work and treatment runs about $1,000. The treatment alone is usually about $500. These are rough estimates – be sure to contact your veterinarian for more specific costs.
Why Do Dogs Need to Be Kept Quiet During the Heartworm Treatment Period?
After treatment, the worms begin to die. As they die, they break into pieces. If your dog is active, a piece of the dead worm can cause a blockage in the blood vessels and cause death. For this reason it is imperative you keep your dog quiet for several months during and after the treatment period. Studies have shown most dogs who die after heartworm treatment do so because they were allowed to exercise.
How Can I Prevent Heartworm Disease in My Dog?
There are several different types of preventative medications that will prevent heartworm disease in dogs. All require a veterinarian’s prescription. There are monthly pills, monthly topicals to rub on the skin as well as a six-month injectable. A year’s supply of heartworm prevention will cost between $35 – $80 (depending on the size of your dog), less than going out for a weekly coffee. Heartworms cause irreparable damage to a dog and the diagnosis and treatment is costly, way more than the cost to prevent heartworm disease.
Is Heartworm Disease Prevention Dangerous?
In the past, plain arsenic was used to prevent heartworm disease in dogs, which had side effects. The preventative used today is a safer product with fewer side effects. If used correctly, heartworm disease preventative products used today are considered safe by most vets.
However, no drug is entirely harmless. Heartworm preventatives are chemical insecticides with the potential for long-term side effects in your dog. Furthermore, there is evidence of growing resistance to preventatives. (American Heartworm Society)
Some veterinarians suggest checking parasite prevalence maps to determine your dog’s risk for getting heartworms.
If My Dog Gets Heartworms and Is Treated, Can He or She Get Them Again?
Yes, your dog can get heartworms multiple times. For this reason, lifetime heartworm disease prevention can be important.
It is highly recommended that you talk with your veterinarian about heartworm disease prevention before making a determination about what is best for your dog.
Do you give your dog heartworm disease prevention medication every month? Why or why not?
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I’m all for heartworm prevention. However don’t lie about the actual cost involved. Heartworm prevention like Heartgard and Interceptor cost $14-$20 each at vet. If you buy a 12 month box this is less. Heartgard is $130 for one 12 month box. That’s for one dog. Also it is required to have an annual heartworm test. This runs $60-80 for an in house test that gives you results at the time of your appointment. Your vet office fee will be $50 – 80 on average for one visit. Heartworms are endemic in the US South. Skipping heartworm prevention shouldn’t even be considered for many dogs. Some that are urban dwellers living indoors might be lower risk. As long as the annual heartworm test is done, skipping the monthly hw dewormer might be ok. You weigh the risk. But really most dogs in the US South should be on hw monthly. It’s too easily transmitted by mosquitoes. As for people with multiple dogs, that’s when these things get ridiculously expensive. For any people doing rescue those seemingly minor costs greatly add up! I hate the pharmaceutical companies charging more than they really should for such an essential necessity. People could take on more dogs as rescues if this stuff was much cheaper.
You bring up some great points, Bonnie! Thank you for the information and yes, it would help rescue organizations if the heartworm prevention medication wasn’t so expensive!