Is heartworm disease a threat to your pet? The prevalence of the disease is increasing in Massachusetts, and myths abound regarding heartworms and your pet’s health. The All Pets Medical Center team addresses seven of the most common myths regarding heartworm disease, to help you better understand the dangers of this hidden mosquito-borne blood parasite.

Myth #1: My pet rarely goes outside and is not exposed to heartworms

Mosquitoes can carry immature heartworms (i.e., larvae), and can sneak into your home, bite your pet, and transmit a disease-causing infection into your pet’s bloodstream. Many people believe their home is safe from mosquitoes, but 25% of cats with heartworm disease live indoors only. Puppies can become infected in the womb if their mother has heartworm disease.

Myth #2: Heartworms are tiny and don’t cause big problems for pets

Adult heartworms can grow up to 14 inches long, and obstruct blood flow in arteries, blood vessels, and the heart, resulting in decreased oxygen availability for the body and life-threatening blockages. A dog or cat’s immune system will try to attack the heartworms at developmental stages, causing inflammatory tissue damage. The combination of these changes can result in heart failure, permanent lung damage, and sudden death from dead or dying worms blocking blood flow. 

Myth #3: My pet acts healthy, so they can’t have heartworm disease

Your pet can be infected for up to two years before they show disease signs. Heartworm larvae spend five to eight months in the bloodstream before they reach their destination and become adult worms. Adult females produce “microfilariae,” which are released back into the bloodstream, and repeat the developmental stages to adulthood. Signs of advanced heartworm disease can include:

  • Decreased appetite and weight loss
  • Coughing, wheezing, difficulty breathing, or shortness of breath
  • Exercise intolerance
  • Vomiting
  • Nosebleeds
  • Fluid accumulation in the lungs or abdomen
  • Blockages in arteries or vessels resulting in sudden death

Early diagnosis allows for a greater chance of full recovery, so routine testing of your pet is vital.

Myth #4: Diagnosis of heartworm diseases in pets is complicated

Although heartworms are tiny blood parasites, testing is highly accurate in dogs with a developed female worm. In dogs, a small blood sample is taken to check for an antigen against the female worm. Positive tests are repeated to ensure they are accurate.

Cats are not natural heartworm hosts, and have a vigorous immune response that prevents 75% of larvae from reaching adulthood. Getting an accurate test result is a bit more complicated, and blood is typically sent to a laboratory for accurate results.

Myth #5: Heartworm treatment in pets is similar to routine deworming

Heartworm treatment is significantly more costly and complex than routine deworming for intestinal parasites. The American Heartworm Society has detailed guidelines for heartworm disease treatment in dogs and cats, which starts by staging disease severity with a complete blood panel, and chest X-rays or echocardiogram testing. Pets with severe signs may need stabilization prior to treatment.  

The first step in treating dogs and cats is to use heartworm preventive to kill microfilariae, and antibiotics to eliminate heartworm-associated bacteria. The next step for dogs involves painful multiple intramuscular injections of an arsenic-based derivative to kill adult heartworms. The complete treatment protocol can take months, during which dogs with heartworm disease require strict exercise restriction to avoid sudden blood flow blockages, and minimize heartworm-related tissue damage.

Unfortunately, a licensed product to kill adult heartworms is NOT AVAILABLE FOR CATS, which makes heartworm prevention essential. The medical option for cats is to minimize inflammatory damage from heartworm disease with long-term corticosteroids, with the hope that their immune system will slowly and safely kill adult heartworms over time. 

Myth #6: Heartworm preventives for pets are dangerous and difficult to use

Heartworm preventives are much safer for your pet than the disease, or the treatment. Heartworm preventives are rigorously tested and specifically designed to prevent heartworm larvae from developing into adult worms. The products are available in a monthly oral or topical form, or a biannual or annual injection for dogs. The All Pets Medical Center team recommends year-round heartworm prevention, because mosquitoes can adapt to the cold, or overwinter indoors, and their season is increasingly variable.

Myth #7: Regular heartworm testing isn’t necessary if my pet is on preventive

A pet on regular heartworm prevention has a significantly lower risk of developing heartworm disease. However, no preventive is 100% effective, your pet may not ingest the full dose, or you may apply topical preventives incorrectly, administer the medication late, or forget a monthly dose. The American Heartworm Society recommends annual heartworm testing to ensure that a heartworm infection is caught before disease signs develop. 

The potential danger of heartworm disease lurks inside every mosquito. Contact the All Pets Medical Center team to keep your pet safe from heartworm disease with regular testing and prevention.