During your pet’s wellness visits with their primary care veterinarian, you probably and hopefully always discuss heartworm prevention. While it might seem easy to opt-out of heartworm medication because: your cat is an indoor pet and doesn’t get bit by mosquitoes (that spread the disease), it is winter and there are no mosquitoes, or the monthly medication is too expensive.

Those assumptions are often wrong and can be dangerous and costly, especially since animals can be infected all-year-long (not just during hot weather) in all 50 states. Indoor pets can still be infected by mosquitoes that enter the home or if a cat or dog is outside even for a brief moment.

Ongoing heartworm prevention, including annual exams and medication prescribed through your primary care veterinarian, can prevent life-threatening heart and lung conditions.

Here at The COVE, we see patients that suffer from congestive heart failure and other illnesses related to heartworm. However, it is one disease that can be easily prevented through medication. So, if your dog or cat isn’t on heartworm medication, now is the time to visit your primary care veterinarian. If you need more convincing, please continue reading.

What is Heartworm?

Heartworms (Dirofilaria immitis) are parasitic roundworms that live in the heart, lungs, and associated blood vessels of affected animals, causing severe lung disease, heart failure, and possible damage to other organs. When a mosquito takes blood from an infected animal, it also ingests baby worms, developing and maturing into “infective stage” larvae over 10 to 14 days. When the infected mosquito bites a dog or cat, the infective larvae are deposited onto the surface of the animal’s skin and enter the new host through the mosquito’s bite wound. While it takes about six months for the larvae to mature, once they are adults and reproduce offspring, heartworms can live five to seven years in dogs and two to three in cats.

If left untreated in canines, heartworm numbers can increase, and dogs have been known to harbor several hundred worms in their bodies. Heartworm disease causes lasting damage to the heart, lungs, and arteries, affecting a dog’s health and quality of life long after the parasites are gone.

Felines are an atypical host for heartworms, and most worms do not survive to the adult stage. Many cats affected by heartworms don’t have any adult worms. Therefore, heartworm disease often goes undiagnosed in cats. However, it’s critical to know that even immature worms cause damage in the condition called heartworm associated respiratory disease (HARD). The typical medication used to treat heartworm infections in dogs can’t be given to cats, so prevention is the only means of protecting your kitty from heartworm disease.

Hopefully, this is enough information to convince you of the importance of heartworm prevention, but we will continue with what happens to infected pets.

Signs and Symptoms of Heartworm Disease

Here a few common symptoms of heartworm in dogs, as cats usually don’t exhibit many symptoms.

  • A mild persistent cough
  • Reluctance to run, play and exercise
  • Fatigue after moderate activity
  • Decrease in appetite
  • Difficulty breathing
  • Weight loss

If your dog or cat is exhibiting any of these symptoms, please seek care from your primary care veterinarian.

When a pet is tested positive for heartworm, the disease is divided into four stages.

Stage 1

  • Little to mild symptoms such as an occasional cough

Stage 2

  • Mild to moderate symptoms, including occasional cough and tiredness after moderate activity

Stage 3

  • Symptoms are more severe and noticeable such as a sickly physical appearance, a persistent cough, and fatigued after mild activity
  • Difficulty breathing
  • Additionally, severe conditions can start to develop including congestive heart failure

Stage 4

  • At this point, the symptoms are severe, and your pet is severely ill
  • Dogs develop caval syndrome when a large mass of worms blocks the heart. Caval syndrome is life-threatening, and the heartworms will need to be removed surgically.

Testing and Treatment

Heartworm disease is detected through blood tests performed by a veterinarian; another reason for routine veterinary visits and blood work! Additionally, at stages two and three, heart and lung changes from heartworm disease can be seen on radiographs (x-rays).

Treatment for heartworm disease is to kill all of the heartworms through various forms of medication administered by a veterinarian. Treatment is dependent on the stage of the heartworm disease. Your veterinarian will follow a protocol to kill all adult and immature worms through medication while carefully monitoring your dog for any side effects.

As heartworm disease progresses without treatment, pets can develop heart failure. If your pet is suffering from heart and lung-related illnesses from heartworm disease, your veterinarian might refer your pet to a board-certified veterinary cardiologist like The COVE’s Merrilee T. Small, DVM, DACVIM (Cardiology). For more information about managing heart failure and heart disease, please read our previous blogs on the topic.

Prevention Is The Best Medicine!

We really can’t stress this enough – your dog and cat need to be on regular heartworm prevention medication. Whether it be a monthly medication or injection, it is the most effective way to avoid heartworm disease and lung and heart complications. Additionally, monthly medication is far less expensive than treatment for a pet’s heartworm disease (including diagnostics and possible hospitalization).

For more information about heartworm disease, please visit the American Heartworm Society’s website. 

We hope you find this information helpful and insightful. Please remember that, if your pet needs advanced cardiac care, Dr. Small and her team are here to help. For additional questions, you can reach The COVE at 757-935-9111. And remember, in an emergency, we are open 24/7, and no appointment is ever needed.

About Us

The COVE’s veterinarians and staff wholeheartedly embrace the core values of community, collaboration, commitment, compassion, and integrity. This focus ensures that pets, the people who love them, and their primary care veterinarians have as positive and affirming a healthcare experience as possible, regardless of the circumstances that bring us all together.