Heartworm disease is a serious, progressive disease, and our team at Billings Animal Family Hospital is here with the information you need to keep your pet safe, including:

  • How heartworms are transmitted
  • How to protect your pet from heartworms
  • Treatments available if your pet tests heartworm-positive

This dangerous condition is life-threatening, but preventable, and you have the power to keep your pet heartworm-free. We answer pet owners’ most frequently asked questions.

Question: What are heartworms and how do pets get them?

Answer: Adult heartworms look like foot-long spaghetti noodles, and are transmitted primarily through an infected mosquito’s bite. Immature heartworms (i.e., microfilariae) enter your pet’s bloodstream through the bite wound, and travel through their bloodstream for approximately six months, until they mature into adult heartworms. The adults continue to grow and reproduce, infecting your pet’s heart, lungs, and pulmonary blood vessels. 

  • Dogs — Once inside your dog, and after traveling and maturing, the adult heartworms can live inside your dog’s heart for five to seven years, causing a wide range of health problems.
  • Cats — Heartworms do not thrive as well inside a cat’s body. They can reach adulthood in about seven to eight months, but rarely reproduce, and the few worms that do mature usually live only two to four years. However, only a few worms can significantly damage your cat’s small heart and lungs.
  • Ferrets — Ferrets also are susceptible to heartworm infections, but microfilariae usually are produced in only about half of heartworm-infected ferrets, so their worm load is small. 

Q: What are heartworm disease signs in pets?

A: Heartworm disease severity in dogs depends on the number of worms, how long the dog has been infected, and how their body responds to the infection. Heartworm signs may not be obvious in recently infected or inactive dogs, but those who have been infected for a long time, or are extremely active, often will show visible signs that include: 

  • Mild, persistent cough
  • Reluctance to exercise
  • Fatigue after exercise
  • Decreased appetite
  • Weight loss

Because most worms in cats do not survive to the adult stage, not all cats with heartworm disease show symptoms. If cats do show signs, they will include:

  • Vomiting
  • Decreased activity 
  • Decreased appetite and weight loss
  • Respiratory problems (e.g., trouble breathing, increased respiratory rate, and cough) 

Q: How is my pet checked for heartworm disease?

A:  Blood work is required to make a heartworm disease diagnosis. The blood testing can be performed in-house, but often an outside laboratory will need to perform more specific testing to ensure a correct diagnosis. This is because in-house testing may be limited, since only adult female heartworms can be detected. Only immature heartworms and adult males may be present, and cause a false-negative result. 

Q: How can early heartworm detection improve a pet’s prognosis?

A: Because heartworm disease is progressive, the earlier the detection and treatment, the better your pet’s prognosis. The American Heartworm Society recommends testing pets every 12 months, and ensuring year-round heartworm prevention. Unfortunately, no heartworm treatment is available for cats, so prevention is key.

Q: Is treatment available for heartworm-positive pets?

A: Yes—but only for dogs. The earlier your dog is treated, the more likely a positive outcome. Heartworm disease treatment  includes:

  • Antibiotic therapy — Antibiotic therapy is generally instituted for approximately 60 days, to reduce side effects and treat a bacteria carried by the worms.
  • Medications — Deep, painful injections of an arsenic-derived medication are administered to kill adult worms.
  • Exercise restriction — Dogs must be totally exercise restricted, to reduce the risk of potentially fatal exercise-induced side effects caused by the dying worms lodging in the lungs and causing a blockage.
  • Surgery — Surgical removal of the pet’s heavy worm burden may be an option in some extreme cases.

Q: How can pets be protected from heartworm disease?

A: A variety of safe, effective heartworm preventives in topical, oral, and injectable forms are available, and our veterinary team can help you choose the option that best suits you and your pet. Remember, no preventive treatment is available for cats. 

You can also help mitigate your pet’s risk of heartworm infection by eliminating standing water areas, avoiding shady outdoor spots that attract mosquitoes, and repairing tears in window and door screens, to prevent the pests from entering your home.

No pet—or owner—should suffer through the long and complex heartworm disease treatments, and no pet should lose their life because they were not protected, when the disease is easily prevented. We want to ensure your pet stays safe and heartworm free, so contact our team at Billings Animal Family Hospital to schedule an appointment for their heartworm test.