As a dog parent, caring for your furry friend begins with preventative health. One of the most important aspects of preventative health for dogs is starting heartworm prevention medication and ensuring annual heartworm blood testing is performed.

Treating heartworm disease in dogs can be a time-consuming, costly, and difficult road to recovery. That's why prevention is key! 

Below, learn more about preventing heartworm in dogs to keep your dog happy and healthy.

Key Takeaways:

  • Heartworm disease in dogs is caused by an infestation of parasitic worms in the heart and bloodstream.
  • Dogs get heartworms through mosquito bites, with the larvae transmitted from infected mosquitoes.
  • Preventing heartworm disease in dogs is vital and can be achieved through regular use of preventive medications prescribed by a veterinarian.

What is Heartworm in Dogs?

Heartworm in dogs refers to an infestation of parasitic worms that reside in the heart and bloodstream of dogs. These worms, known as heartworms, can cause severe health issues and, if left untreated, can be fatal.

How Do Dogs Get Heartworms?

Dogs are the perfect host for heartworm, with heartworm larvae living in their bloodstream. These larvae, known as microfilariae, are transmitted to the mosquito when it bites a dog. The larvae in the mosquito then become infected, leaving the infected mosquito to bite another dog and thus, leading to heartworm disease.

These tiny parasites take several months to form into adult heartworms, eventually spreading throughout a dog's body. This is a slow process, which means many dogs can live with heartworm for a long time before showing any symptoms.

Signs & Symptoms of Heartworm in Dogs

In the early stages, dogs with heartworm disease may not show any visible symptoms. However, as the disease progresses, common signs and symptoms may include:

Test Your Knowledge of Heartworm

Test Your Knowledge of Heartworm
1. Dogs can get heartworms from other animals
2. Once dogs are treated for heartworm, they become immune to future infections
3. Heartworm disease is only a problem in some states
4. Heartworms can only live inside a pet for 6 months
5. Heartworm disease can be deadly
6. My cat cannot get heartworm disease
7. My pet only needs heartworm preventative in the spring and summer months
8. I don’t need a prescription for my dog’s heartworm prevention
9. My pet does not need an annual heartworm test if they receive heartworm prevention
10. Heartworm treatment costs about the same as prevention

Your Score is

1. Dogs can get heartworms from other animals | FALSE

Heartworms can only be transmitted to your pet by infected mosquitoes. Mosquitoes carry heartworm larvae that they have picked up from infected animals. The larvae develop in the mosquito, which can then be passed on to dogs and cats when bitten by the infected mosquito. 

When a pet is bitten, the heartworm larvae are transferred onto their cat or dog’s skin, entering the bloodstream and migrating to the heart and lungs. It takes approximately six months for larval worms to migrate, mature, and reproduce.
2. Once dogs are treated for heartworm, they become immune to future infections | FALSE
Unfortunately, dogs can be infected with heartworm multiple times.
3. Heartworm disease is only a problem in some states | FALSE
Heartworm disease has been detected in all 50 states.
4. Heartworms can only live inside a pet for 6 months | FALSE
Heartworms can live in dogs for up to seven years and cats for up to three years.
5. Heartworm disease can be deadly | TRUE
Once heartworm larvae enter a pet’s bloodstream, they reproduce rapidly, with multiple generations affecting the lungs and heart. Heartworm causes severe inflammation, which a pet’s immune system will try to fight off.  Heartworms also prevent normal blood flow, which leads to congestive heart failure. Without treatment, heartworm disease will worsen and become deadly.
6. My cat cannot get heartworm disease | FALSE
While heartworms are most common in dogs, cats can also be infected. If an infected mosquito bites a cat, heartworms can survive in their system, but not reproduce. Unfortunately, even a few worms can cause significant inflammation in a cat and there is no approved medication to kill adult heartworms in cats. Heartworm-related health problems for cats include respiratory disease (HARD) with asthma-like symptoms that can become life-threatening.
7. My pet only needs heartworm preventative in the spring and summer months | FALSE
The American Heartworm Society recommends year-round treatment for heartworm for dogs and cats. Options that your veterinarian may recommend include monthly chewables, injections or topicals.
8. I don’t need a prescription for my dog’s heartworm prevention | FALSE
The U.S. Food and Drug Administration (FDA) states that any heartworm medication is to be prescribed on the order of a licensed veterinarian. Your veterinarian will prescribe a heartworm preventative that is recommended for your pet’s species, weight, and lifestyle.
9. My pet does not need an annual heartworm test if they receive heartworm prevention | FALSE
Annual testing is necessary for pets, even when they are on a year-round heartworm prevention protocol, to make sure that the medication is working. Heartworm medications are very effective, but pets can still become infected. If you miss just one dose of a monthly medication—or give it late—it is leaving a window open to infection.
10. Heartworm treatment costs about the same as prevention | FALSE
A year’s worth of prevention is small in comparison to the cost of treatment. Heartworm treatment is available for dogs but is lengthy, expensive, and painful. A medication to kill adult worms must be injected into a dog’s muscles. Several treatments spaced 30 days apart may be needed, as well as with other medications to reduce inflammation and kill bacteria. Treatment usually lasts several months and dogs need to be kept inactive to minimize the risk of dying worms lodging in their lungs which can lead to sudden death.

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How Are Dog Heartworms Diagnosed?

To diagnose dog heartworms, veterinarians typically conduct a blood test as part of the dog's annual wellness exam. This blood test specifically looks for heartworm antigens, which are proteins produced by adult female heartworms. By detecting the presence of these antigens, the test can confirm if the dog has been infected with heartworms. 

Annual testing is highly recommended, even for dogs on preventive medication, as it plays a crucial role in identifying the presence of heartworms at an early stage. Early detection allows for prompt treatment, increasing the chances of successful recovery and minimizing potential complications.

Heartworm Treatment for Dogs

If your dog has been diagnosed with heartworm disease, it's important to begin treatment promptly. Heartworm disease can worsen the longer a dog has been infected. Treating heartworm in dogs can be a lengthy and difficult process, which can often take months to treat. According to the American Heartworm Society, dogs with heartworm should first be treated with antibiotics as a pre-treatment.

After a round of antibiotics, a medication known as Melarsomine (in an injectable form) treats heartworm disease in dogs. This medication is split into three injections, staggered over several months. Melarsomine is highly effective in most mild-to-moderate cases of heartworm disease. However, these injections may not be enough for dogs with severe cases of heartworm disease. Surgery may be required in these cases.

If your dog has been diagnosed with severe heartworm, a quality-of-life consultation can be helpful to make them as comfortable as possible during treatment.

How to Prevent Heartworm Disease in Dogs

Preventing heartworm disease is essential to ensure the well-being of dogs. The primary prevention method is through the regular use of preventive medications prescribed by a veterinarian

These medications are available in various forms, including monthly chewable pills or topical treatments, and are designed to be administered year-round. By consistently administering these preventive medications, dog owners can effectively protect their furry companions from heartworm infection. It's important to follow the veterinarian's instructions and maintain a regular schedule to achieve maximum effectiveness. 

In addition to preventive medications, annual heartworm testing is crucial. This testing helps detect any potential infection early on, allowing for immediate treatment if necessary. By combining preventive measures with regular testing, dog owners can effectively safeguard their pets' health and well-being, providing them with the best defense against heartworm disease.


Protecting your furry friend from dangerous heartworm disease is easy with help from BetterVet. During your pet's annual exam, we'll help you select the best preventative medication for your dog and perform annual blood testing for heartworm. 

What are you waiting for? Make sure your furry friend is safe from pesky heartworms! Consult with a BetterVet veterinarian today!

Frequently Asked Questions

Can heartworms in dogs be detected immediately?

No, it takes 6-7 months for a blood test to detect heartworms in dogs, as they need time to mature. Detecting heartworms early increases treatment success.

What other ways can I help prevent heartworm for my dog?

Besides preventative medications, reducing mosquitoes in your home and yard can help prevent heartworm disease. Using pet-friendly insecticides can help decrease mosquito populations.

If one pet in my household has heartworm, are the other pets at risk too?

Heartworms can't be transmitted between pets. They're only transferred through mosquito bites. All pets should be on proper preventative medications.

How often should I give heartworm prevention to my dog?

Heartworm prevention is typically given monthly, year-round, especially in mosquito-prone areas. The frequency depends on the product used and should be discussed with your veterinarian.