Heartworm disease is regularly reported throughout Oregon, and all pets are at risk, including those who live indoors. While the condition is preventable, heartworm disease can be fatal if the appropriate precautions aren’t taken. Our team at The Pet Clinic of Salem would like to help you understand more about heartworm disease, so you can protect your pet.

The basics of heartworm disease in pets

Heartworms are parasites that can significantly damage an infected animal’s heart, lungs, and vasculature. Pets most commonly infected include dogs, cats, and ferrets, although wild animals, such as foxes, wolves, coyotes, raccoons, and opossums, can also be infected. Heartworms are transmitted from animal to animal by mosquitoes. 

  • Transmission — When a mosquito takes a blood meal from an infected animal, baby heartworms (i.e., microfilariae) enter the mosquito’s system, where they take about two weeks to become infective larvae. At that time, the mosquito can transmit them to another animal, including your pet, when they bite and take a blood meal. 
  • Life cycle — Once inside, the infective larvae migrate through your pet’s body for the first three months, eventually reaching their lung blood vessels. During the next three months, the infective larvae mature, growing as long as 14 inches in some cases. Dogs are natural hosts, which means the worms can mature, mate, and produce offspring, which typically occurs about five to seven months post-infection. Cats and ferrets are atypical hosts, which means heartworms rarely develop to adulthood, but they still cause significant damage to the pet’s heart and lungs. Heartworms can survive for five years or more in dogs, and for several months to years in cats and ferrets.

Heartworm disease signs in pets

Most pets don’t show signs in the initial heartworm infection stages, and then generalized signs, including lethargy, weight loss, and exercise intolerance, as the disease progresses. Active pets, and those with underlying health issues, are more likely to show signs. Other signs are species-specific.

  • Dogs — A mild, persistent cough can be a sign in dogs. In addition, they may develop a distended belly as their heart fails, losing the ability to effectively pump blood, and resulting in fluid accumulation in their abdomen. Dogs who have a large worm load can experience a sudden blood flow blockage inside their heart, suddenly causing labored breathing, pale gums, and coffee-colored urine. This condition, called caval syndrome, can be fatal if the heartworms aren’t immediately surgically removed.
  • Cats — Cats may exhibit asthma-like attacks and intermittent vomiting. The heartworms reside in the cat’s lung vasculature, resulting in heartworm associated respiratory disease (HARD). In addition, immature worms can trigger a severe inflammatory response in the cat’s smaller lung vasculature, airways, and tissue.
  • Ferrets — Ferrets exhibit signs similar to those in dogs, but their signs typically manifest sooner, since their heart is so small.

Testing for heartworm disease in pets

Early detection improves your pet’s survival chances if they are infected by heartworms. Testing methods include:

  • Antigen tests — Antigen tests, which detect specific proteins released by the adult female heartworm, are typically highly accurate in dogs. The proteins can be detected about five months after the initial infection occurs.
  • Antibody tests — Antibody tests detect exposure to heartworm larvae. Cats and ferrets typically need antigen and antibody testing for an accurate diagnosis.
  • Microfilariae test — Microfilariae can be visualized in whole blood, but this method is relatively insensitive, and should be used only as a supplemental test for dogs.
  • Ultrasound — In some cases, ultrasound is needed to diagnose heartworms in cats and ferrets.

Treating heartworm disease in pets

All pets infected by heartworms should be activity-restricted, since physical exertion can exacerbate the damage the heartworms inflict on your pet’s heart and lungs. Our veterinary professionals will then stabilize your pet, to ensure they are healthy enough to undergo treatment. Unfortunately, no safe, effective treatment has been approved for heartworm disease in cats and ferrets, and their condition will need regular monitoring. For dogs, we will establish a treatment protocol that will be carried out slowly over several months. Worms that die off too fast can cause a blockage in your dog’s heart, and become life-threatening, so your dog’s treatment must be carefully monitored.

Preventing heartworm disease in pets

Prevention is the best way to protect your pet from heartworm disease. Steps include:

  • Reduce exposure — You can’t completely prevent your pet from mosquito exposure, but you can keep them inside in the late afternoon and early evening when mosquitoes are most active. You should also eliminate any standing water around your house.
  • Routine testing — Your pet should be tested for heartworms at least once a year.
  • Prevention medications — Your pet should receive heartworm preventives year-round. Medications are available in multiple forms, including pills, topical applications, and injectables.

Heartworm disease is a dangerous, potentially life-threatening disease, but certain precautions can protect your pet from these parasites. If you would like your pet tested for heartworms, contact our team at The Pet Clinic of Salem, so we can ensure they have a clean bill of health.