Heartworm prevention has become a standard of preventive care for pets in the United States. However, more than 1 million pets in the US are believed to be heartworm positive, and that number is growing.
Although some parts of the country are more severely affected than others, heartworm disease has been diagnosed in all 50 states.
You may have to have your dog treated for heartworms in cases such as these:
If you have adopted a heartworm-positive dog
If you have missed your dog’s monthly dose of heartworm prevention
If you were unaware of heartworm disease until your dog tested positive
No matter the reason, if your dog has heartworm disease, here are the costs you can expect for each step, from diagnosis to treatment.
1. The Positive Heartworm Test
To be treated for heartworms, a dog must first test positive for the disease.
The most common heartworm tests can be done right in your vet’s office, where the results may be available within minutes. It’s recommended that all dogs be tested annually for heartworm disease, even if they are on heartworm prevention.
A heartworm test may range from approximately $35 to $75.
2. The Confirmatory Test
If the in-office test is positive, your veterinarian will likely recommend a confirmatory test to verify the positive test result.
Since no test is perfect—and heartworm treatment is expensive and can have significant side effects—your veterinarian will want to be certain that treatment is necessary before proceeding.
Confirmatory tests may vary, and generally range in price from $20 to $40.
3. Determining the Stage of Heartworm Disease
Once a dog has been fully confirmed as being positive for heartworm disease, additional tests such as chest x-rays, and sometimes, echocardiography (ultrasound of the heart), are done to stage the severity of disease.
Staging helps the veterinarian assess the level of damage that has already been done by the heartworms, as well as determine specific treatment and post-treatment regimens.
The cost of chest x-rays generally varies from $125 to $200, and the cost of an echocardiogram may vary from $500 to $1,000.
4. Initial Treatment
Treatment generally begins the first day after a positive diagnosis of heartworm disease.
Initial treatment steps are taken in an effort to:
Weaken adult heartworms
Eliminate immature heartworms
Decrease the risks associated with melarsomine (the medication that is used to kill the adult heartworms)
Doxycycline and Steroids
Before melarsomine is administered, affected dogs are usually put on doxycycline ($30 to $150), which is an antibiotic that helps to weaken the heartworms.
Dogs that are showing symptoms of disease, such as coughing or exercise intolerance, are generally started on a steroid ($10 to $40) to help reduce inflammation.
The cost of doxycycline and steroids may vary depending on the size of your dog.
A prescription heartworm preventative is usually administered on days 1 and 30, to kill heartworm larvae. A month-long waiting period is observed after the initial 30 days of treatment. Heartworm tablets typically cost $6 to $18.
It’s important to note that as soon as a dog is diagnosed with heartworm disease, exercise restriction should ensue. Exercise restriction generally consists of strict crate rest.
5. Final Treatment Stages
The final stages of heartworm treatment serve to kill the adult heartworms.
This “adulticide” treatment generally involves three injections of melarsomine, the medication that is the mainstay of heartworm treatment.
On days 60, 90, and 91 of the treatment process, an injection of melarsomine is administered deep into the lumbar musculature of your dog’s back. The dosage of melarsomine is weight-dependent.
A round of steroids ($10 to $40) is generally prescribed for several weeks after each injection.
A series of melarsomine injections may cost anywhere from approximately $500 to $1,500, depending on the weight of your dog.
Strict exercise restriction should continue for six to eight weeks after the final melarsomine injection.
6. Follow-Up Testing
Approximately one month after the third melarsomine injection, your dog’s blood should be evaluated for the presence of microfilariae (a larval stage of the heartworm, which is visible with a microscope). The microfilaria test costs $20 to $40.
If the microfilaria test is positive, the dog should continue heartworm prevention for four weeks and then be retested.
Approximately three months after the third melarsomine injection (one year after the initial diagnosis of heartworm disease), a heartworm test is run ($35 to $75). If it is positive, the dog should be treated with another round of doxycycline ($30 to $150), followed by two injections of melarsomine 24 hours apart ($500 to $1,000).
Complications That May Prevent Melarsomine Treatment
If your dog is very ill or weakened due to heartworm disease, your veterinarian may not consider him or her to be a good candidate for melarsomine treatment.
Dogs that are very severely affected by heartworm disease may develop a complication known as caval syndrome. Caval syndrome occurs when adult heartworms occupy so much of the right side of the heart that they block the blood vessels that are responsible for filling it with blood.
Caval syndrome is characterized by collapse, shock, and destruction of red blood cells. It is usually fatal.
The only form of treatment is surgical removal of heartworms from the heart, which must be done on an emergency basis. This surgery can cost $3,000 to $6,000.
Cost-Benefit of Heartworm Prevention vs. Treatment
The cost of heartworm prevention is low when compared to the cost of having to treat your dog for heartworms. Heartworm treatment is undoubtedly expensive. It is also uncomfortable for the dog, has significant side effects, and requires prolonged activity restriction.
Melarsomine treatment must be preceded by a series of diagnostic tests and treatments that may cost anywhere from an additional $100 to over $1,000. These costs will vary depending on the size of your dog, the severity of disease, and the recommendations of your veterinarian.
Then, the cost of melarsomine heartworm treatment may vary from $500 to $1,500. If the initial doses of treatment are not completely effective, repeat treatment may be required, which may cause this cost to double.
Thankfully, there are readily available, affordable, prescription medications that are highly effective at preventing heartworm disease. Heartworm prevention requires a prescription from your veterinarian, and it is generally administered monthly as a tablet that costs between $6 and $18 per month.
You can also opt for an injection. ProHeart 6 is a heartworm prevention shot that lasts six months ($50 to $150 per six months), and ProHeart 12 is a shot that is given annually ($75 to $350 per year).
It’s generally recommended that heartworm medications be administered year-round to best prevent against these deadly parasites.
The Veterinary Fee Reference. 9th ed., American Animal Hospital Association Press, 2015