<img src="Terrier-Header.jpg" alt="Brown and black terrier">

Heartworm Disease

Heartworm disease is serious, life threatening, and completely preventable. Heartworms cause severe lung disease, heart failure, other organ damage, and death in dogs, cats, and ferrets. Heartworm is treatable in dogs, but there is no cure for heartworm disease in cats.

HSSC’s Animal Clinic offers in-house blood tests that can confirm if a dog has heartworm disease in a few minutes. The Animal Clinic also sells heartworm preventives at a fraction of the price of other providers. See Heartworm Pricing and Schedule an Appointment.

Heartworm affects far too many canines, especially in Southwest Florida. HSSC is one of the few no-kill shelters that will take on the task of healing a heartworm positive dog. Every adoptable dog receives a blood test. If the dog is positive for heartworms, HSSC will treat the dog. Treatment is costly and time-intensive, and, as a result, many shelters are unable to treat heartworm dogs. HSSC is fortunate to be able to do so. Hundreds of animals have been treated and given a second chance. Read some of their Heartwarming Tails below.

Heartworm FAQs

Here are the most frequently asked questions about heartworm disease. For additional information and resources, please click to visit the American Heartworm Society’s website

How do dogs get heartworm?
Only by the bite of an infected mosquito. There’s no other way dogs get heartworms. And there’s no way to tell if a mosquito is infected. That’s why prevention is so important. A bite from just one mosquito infected with the heartworm larvae will give your dog heartworm disease. Once a dog is bitten by an infected mosquito, it takes about seven months for the larvae to mature into adult heartworms. They then lodge in the heart, lungs, and surrounding blood vessels and begin reproducing. Adult worms can grow up to 12 inches in length, can live five to seven years, and a dog can have as many as 250 worms in its system.
Is heartworm a regional problem?
While heartworm is prevalent in warm climates (like southwest Florida), heartworm disease has been reported in all 50 states. It’s now found in areas where veterinarians used to say, “Oh, we don’t have heartworm disease.” Areas like Oregon, California, Arizona, and desert areas—where irrigation and construction are allowing mosquitoes to survive. And if you have mosquitoes and you have animals, you’re going to have heartworms. It’s just that simple.
Can people get heartworms from their dogs?
No, heartworm can only be passed on by mosquitoes. It’s a specific parasite that only affects dogs, cats, ferrets, and other mammals. In rare cases, heartworms have infected people, but it does not complete its life cycle. The heartworm will migrate to the lungs and cause a round lesion that looks like a tumor. But these are very rare cases.
If one of my dogs has heartworms, can he give it to my other dogs?
No. The only way heartworms are transmitted is through the bite of an infected mosquito. Even if an uninfected mosquito bit your infected dog, and then bit your other uninfected dog the same night, he wouldn’t transmit the parasite from one dog to the other. That’s because when a mosquito bites an infected animal, the heartworm needs to undergo an incubation period in the mosquito before the mosquito can infect other animals.
Is it okay to adopt a dog with heartworms?
Heartworm is a very common problem in animal shelters today, and public shelters rarely have the money to treat heartworm disease. It’s perfectly fine to adopt a dog with heartworms, but you have to be dedicated to having the disease treated appropriately, because it’s a horrible disease that can lead to a dog’s death if left untreated. Once treated, animals can lead full and active lives. Fortunately, HSSC has the means to treat heartworm positive dogs. All heartworm positive dogs from HSSC are treated for heartworm before adoption. Hundreds of dogs have been treated at HSSC and are now happy and healthy in their furever homes.
How can I prevent my dogs from getting heartworms?
For less than the cost of going to Starbucks for a weekly coffee, you can prevent heartworm disease in your dog. There are monthly chews and pills, topicals that you put on the skin, and there’s also a six-month injectable product. The damage that’s done to the dog and the cost of the treatment is way more than the cost to prevent heartworm disease. A year’s supply of heartworm preventive will cost about $35 to $80, depending on a dog’s weight. The Animal Clinic of HSSC sells heartworm preventives at very affordable prices.
What are the symptoms of heartworm infestations in dogs?
Initially, there are no symptoms. But as more and more worms crowd the heart and lungs, most dogs will develop a cough. As it progresses, they won’t be able to exercise as much as before; they’ll become winded easier. With severe heartworm disease, abnormal lung sounds can be heard, dogs can pass out from the loss of blood to the brain, and they can retain fluids. Eventually, most dogs will die if the worms are not treated. Only a blood test can confirm if a dog has heartworms. Every dog should be tested annually.
If my dog has heartworms, what’s the treatment? How much will it cost? 
The drug that you treat with is called Immiticide. It’s an injectable, arsenic-based product. The dog is given two or three injections that will kill the adult heartworms in the blood vessels of the heart. The safest way to treat heartworms includes an extensive pre-treatment workup, including X-rays, blood work, and all the tests needed to establish how serious the infection is. Then the dog is given the injections. With all the prep work, it can run up to $1,000. But just the treatment can be done for about $300 in some areas.
Why do I have to keep my dog quiet during the several months he’s being treated for heartworms? 
After treatment, the worms begin to die. As they die, they break up into pieces, which can block the pulmonary vessels and cause death. That’s why dogs must be kept quiet and sedentary during the treatment and then for several months afterward. Studies have shown that most of the dogs that die after heartworm treatment do so because the owners let them exercise. It’s not due to the drug itself.
If my dog is diagnosed with heartworms, can I just give him his monthly preventive instead of having him go through treatment? Won’t that kill his heartworms?
Studies have shown that if you give ivermectin (the most common preventative) monthly to a dog with heartworm disease, after about two years you’ll kill off most of the dog’s young heartworms. The problem is that, in the meantime, all those heartworms are doing permanent damage to the heart and blood vessels. But if there’s no way someone can afford the actual treatment, at least using the preventive monthly could be a lesser alternative.
Can I skip giving my dog his preventive during colder months, when there aren’t any mosquitoes?
The American Heartworm Society recommends year-round heartworm prevention. One reason is, there’s already a serious problem with people forgetting to give their dogs the heartworm preventatives. It’s a universal problem. If you use a preventive year-round, and you miss a month, your dog will probably still be protected. But if you miss more than one or two months your dog could become infected. The other reason not to stop is that many of the preventives today also include an intestinal parasite control for roundworms, whipworms, or tapeworms. You want your dog to be protected against those at all times.
If I don’t treat my dog with heartworms, will he “outgrow” his heartworms?
No. He stands a good chance of dying from the disease.
I’ve heard the treatment for heartworms can be dangerous. Are there any newer, safer alternatives? 
Heartworm used to be treated with plain arsenic, which had many side effects. Current treatment protocols are safer and have fewer side effects, provided the drug is used correctly.
If my dog gets heartworms and is treated for them, can he get them again?
Yes, he can get them again. That’s why regular prevention is so important.
Can cats get heartworm?
Yes, cats can get heartworm from mosquitoes, just like dogs. Heartworm disease is almost always fatal in cats because there is no approved treatment. Even indoor cats need to take a monthly heartworm preventive because mosquitoes can still get inside and bite an indoor cat.

Healing Hearts

Heartworm is only spread through mosquitoes and is very costly to treat. As a result, many shelters are unable to afford the expense. Or, for space reasons, they cannot hold an animal through the minimum three-week treatment protocol. Once the animal is treated and healed, it can be adopted to a loving family and lead a full and active life.

Thanks to generous donors and the support of foundation grants, HSSC has helped rescue, treat, and save hundreds of dogs that were heartworm positive.

Support for the Healing Hearts Fund provided by:

Heartwarming Tails

Heart. Healed. Home. Stories from some of the hearts we’ve healed at HSSC.


Sweet heartworm positive Chihuahua Aly was transported to HSSC from a local high-kill shelter. Now healed, Aly is ready for her next adventure with her new family.


Like most Retrievers, Andrew has no shortage of love to give. This three-year-old Labrador was transported to HSSC from an overcrowded Humane Society in Georgia. Heartworm positive, Andrew required expensive medical treatment and some TLC. After he healed like the champ he is, he found his furever home.


Axel, a two-year-old Poodle mix, was almost a heartworm casualty. He came to HSSC from a hoarding case in December 2015. His heartworm treatments left him seriously ill. He spent two months recovering before being cleared for adoption. Now he's happy in his furever home.

Baby Girl

Three-year old Baby Girl came to us heartworm positive from an overcrowded shelter. Her case was so severe that she almost didn’t survive. Our staff and volunteers spent two months giving Baby Girl the love, care and shelter she needed until she was healthy enough to find her furever home.


Ben was a sweet, two-year-old Labrador Retriever when he arrived at HSSC from Acadiana Animal Aid in Louisiana, and he was also heartworm positive. This loving boy was adopted only one week after HSSC healed his heart. Happy tails, Ben!


Coco is a lucky little Chihuahua who came to HSSC from Sarasota County Sheriff's Office Animal Services when their shelter became overcrowded. He quickly found his furever home after HSSC gave him the treatment and care he needed. Coco is a happy little guy who loves people, and his tail never stops wagging. 


At just two years old, Cookie had already been through more than any dog should ever have to endure. She came from a hoarding case in Louisiana. Not only was she heartworm positive, she was also pregnant. After giving birth and weening her pups (many of whom were adopted from HSSC too!), she was treated for heartworms,  spayed, and adopted.


Delilah was part of a group of dogs rescued from flooding in Mississippi in early 2016. This four-year-old Great Dane was treated for heartworm and was adopted by an HSSC staffer that spring. Delilah can now be seen around the shelter, often with her friend Khloe the Chihuahua.


Kaleb is a big lover-boy who came to HSSC from a local high-kill shelter when they became overcrowded. Being heartworm positive did not bring down this gentle teddy bear’s spirits. A man full of energy and love, he quickly found his furever home only one month after treatment!


Mason was adopted as a puppy from HSSC, but was returned seven years later by his owner. He was thin, had ringworm, and was heartworm positive. We gave Mason the love and medical care he desperately needed, and he was nursed back to health. After a lengthy recovery, he was adopted into a wonderful family with four children.


Peaches came from a hoarding situation in Louisiana. She was terrified and cowered in her kennel at first; she had to be carried everywhere because she wouldn’t walk. Our medical staff realized she was in pain and needed to have her leg amputated. In addition, she had heartworms. After recovering from surgery and heartworm treatment, one of our staffers took extra time to socialize her. Her new family first saw her when they had a birthday party at HSSC.


Pete was heartworm positive and living in a local high-kill shelter. HSSC successfully treated this five-year-old Argentinian Dogo for heartworm, then he met his new family.


Poppin, a two-year-old Rat Terrier, came to HSSC from a hoarding case in Louisiana. His experience had left him extremely shy. The combined efforts of the HSSC staff and volunteer fosters helped him get more comfortable around people. In the meantime, he was treated for heartworm, then adopted.


Walter was transported to HSSC from Acadiana Animal Aid in Louisiana in desperate need of medical attention. He was heartworm positive at only one year old and needed a lot of TLC. Walter went home happy, healthy, and with a healed heart less than one month after being brought to HSSC! 


Zoe was transported to HSSC from a local high-kill shelter. At five years old, this sweet girl survived her treatments and was adopted less than one month later. She’s a lucky girl to have been brought to HSSC and to have found her furever home..
2331 15th Street | Sarasota, FL 34237 | 941.955.4131 | This email address is being protected from spambots. You need JavaScript enabled to view it.
Get Directions

Shelter Hours of Operation
Monday: Closed
Tuesday–Friday: 10am–6pm
Saturday: 10am–4pm
Sunday: Closed
1090 North Tuttle Ave | Sarasota, FL 34237 | 941.364.3605 | This email address is being protected from spambots. You need JavaScript enabled to view it.
Get Directions

Animal Clinic Hours of Operation
Monday: 8am– 5pm
Tuesday: 8am–6pm
Wednesday: 8am–5pm
Thursday: 8am–6pm
Friday: 8am–5pm
Saturday–Sunday: Closed
Closed for lunch each day from 12:30–1:30pm

© 2019 Humane Society of Sarasota County. All Rights Reserved. Privacy Policy | AccessibilitySite Map