You’ve probably seen images of heartworms at your veterinarian’s officethe ones that look like long spaghetti piecesbut do you know how to ensure your pet doesn’t get a heartworm infection? Our team at Dove Mountain Veterinary is here with everything you need to know about this life-threatening disease, including transmission, pet protection, and next steps if your pet tests heartworm-positive. 

Question: How do pets get heartworm disease?

Answer: Heartworms 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 the bloodstream for approximately six months as they mature into adult heartworms about 12 inches long. The adults eventually settle in and around your pet’s heart, lungs, and pulmonary blood vessels, where they reproduce and cause infection. Because a mosquito is required for the cycle, infected pets cannot transmit heartworms to other pets.

Q: How serious is heartworm disease in pets?

A: Heartworm disease is extremely serious, because the parasites can live inside your pet for five to seven years, leading to a wide range of health problems that, left untreated, can be fatal for your pet. While dogs are most at risk, any mammal can develop a heartworm infection, including cats and ferrets. Cats are considered atypical hosts, and tend to be more resistant to heartworms than dogs, but they are still vulnerable, and because they are small, only a few worms can cause a serious problem. 

Heartworm disease signs also differ in dogs and cats.

  • Dogs — In dogs, disease severity depends on the number of worms—which can be hundreds—and infection duration and response. Heartworm signs in dogs are usually not obvious until the infection has progressed, but once visible, may include a mild but persistent cough, inappetence, weight loss, reluctance to walk, and fatigue following exercise.  
  • Cats — Cats seldom show symptoms because of the small number of adult heartworms they host—unfortunately, the first sign of a cat’s heartworm disease is often sudden death. If cats do show heartworm signs, they usually include vomiting, respiratory problems, decreased activity and appetite, and weight loss.

Q: How is my pet checked for heartworm disease?

A:  Checking for heartworm disease requires blood testing that can be performed in-house, but often needs an outside laboratory that can provide more specific testing for an accurate diagnosis. In-house testing detects only adult female heartworms, so your pet may be harboring only immature heartworms and adult males, and the test result is falsely negative. 

Q: Is treatment available for heartworm-positive pets?

A: Heartworm disease is a progressive disease, so the earlier the detection and treatment, the better your pet’s prognosis. The American Heartworm Society recommends testing pets every 12 months for heartworm, and giving year-round preventives. Treatment for heartworm in dogs includes:

  • Antibiotic therapy — Antibiotics reduce side effects and kill a bacteria carried by the worms.
  • Medication — This is the most important component of the treatment, and also the most difficult and painful for your dog. Medication is injected deep into their lumbar muscles, and more than one injection may be required, spread out over weeks. 
  • Exercise restriction  Because the dying worms can lodge in the pet’s lungs and cause a blockage, dogs must be totally exercise-restricted throughout the treatment course.
  • Surgery — Surgically removing a pet’s heavy worm burden is an option in some extreme cases.

Unfortunately, no heartworm treatment is available for cats, so prevention is critical. 

Q: Can pets be protected from heartworm disease?

A: Safe, effective heartworm preventives are available for dogs and cats in topical, oral, and injectable forms. All preventives must be given year-round—only one missed dose can leave your pet vulnerable to infection. 

You may think your pet is not at risk during cold months when mosquitoes are less active, but the risk is never zero. Mosquitoes can hang around bodies of water (e.g., small ponds, flower pots, fountains) in your yard and get inside your home through torn window and door screens. For the same reason, year-round protection is essential for your indoor-only cat. Mosquitoes can also bite your dog when the temperature rises only a little and you are out walking.

Help us spread the word during Heartworm Awareness Month by reminding your friends and family to have their pets tested for heartworm, and ensure they are on a year-round parasite prevention protocol. If your pet is due for their annual heartworm test, contact our Dove Mountain Veterinary team, to schedule an appointment.