As you snuggle on the sofa with your furry pal, you can’t think of anything better. But, little do you know, you and your pet may not be the only ones cuddling—invasive parasites known as heartworms could be wiggling their way through your pet’s body to put a tight squeeze on their circulatory system. In severe cases, heartworms can accumulate in such large numbers that they cause a blockage. There’s nothing heartwarming about that! 

To help pet owners understand the dangers of heartworm disease and what happens if their pet contracts an infection, our Memorial Villages Animal Hospital team wants to share important information about these unpleasant parasites. Read on to learn how to best protect your four-legged friend from the threat of heartworm disease.

How do pets get heartworm disease?

Unlike many other “worm” infections, heartworm disease is not transmitted through contact with contaminated stool or soil. Instead, mosquitoes carry tiny heartworm larvae (i.e., microfilariae) that they deposit on the pet’s skin when they bite. The larvae worm their way into your pet’s body, eventually traveling to the large blood vessels surrounding the heart and lungs. While heartworms most prefer dogs and wild canines, they can infect any mammal, including cats and people. 

What signs will my dog show if they get heartworm disease?

Initially, you won’t notice heartworm disease signs in your dog—in fact, you may not notice any changes for many months. Then, the first disease signs may be a mild yet persistent cough, and fatigue after exercising. As the disease progresses, your pooch’s cough will become worse, and they may also lose weight, experience a decreased appetite, and become less able to exercise. Eventually, heart failure can occur, which can cause the lungs and abdomen to fill with fluid. In severe cases, the heartworms overload the dog’s circulatory system and cause a blockage, resulting in a rapid respiratory rate, pale gums, blood in the urine, a weak pulse, or collapse. Emergency surgery is needed to remove the worms from the heart and surrounding vessels.

What signs will my cat show if they get heartworm disease?

The most common heartworm disease signs in cats are sudden-onset coughing and rapid breathing. Other vague signs can also develop that must be differentiated from a multitude of diseases. Signs include:

  • Vomiting
  • Shortness of breath
  • Lethargy
  • Weight loss
  • Lack of appetite

Occasionally, a cat may become blind, have convulsions or seizures, collapse, or suddenly die. Sudden death is thought to be the result of a reaction in the lungs to the young heartworms, or a reaction to heartworms entering the pulmonary arteries and obstructing blood flow to the lungs.

How will my veterinarian know if my pet has heartworm disease?

Multiple tests are needed to accurately confirm the presence of heartworms in your pet. Diagnostic and disease staging tests may include:

  • An antibody test — This test determines if the immune system has been exposed to heartworms, including late-stage larvae that are not yet adults, or heartworms that have died.
  • An antigen test — This highly specific test detects the presence of adult female heartworms. A pet must have at least two adult female worms to show a positive result, so a negative test can occur if a pet has only a small number of worms, or all the worms are male.
  • Microfilariae exam — A blood sample can be examined under the microscope to find microfilariae. However, fewer than 20% of cats with heartworms have microfilariae in their blood, and the immature larvae are only present for one to four weeks.
  • An eosinophil count — Eosinophils are a white blood cell type that occurs in increased numbers when parasites or allergies are present. This test is not specific to heartworms, so must be looked at in context with other diagnostic tests.
  • X-rays — Chest X-rays provide a view of the heart size and shape, in addition to the size of the pulmonary arteries. Treatment plans are determined based on changes seen on X-rays.

How is heartworm disease treated in pets?

A golden retriever lying calmly on a table while receiving pet pain management from a veterinarian on the right and being petted by a woman on the left.

Heartworm disease treatment in dogs can take months to complete, during which time the dog must be kept severely exercise-restricted. Only short leash walks to use the bathroom are allowed until a month after the final injection has been administered. Limiting exercise helps minimize the potential for adverse side effects.

For cats, no approved heartworm treatment exists.

How can I prevent heartworm disease in my pet?

Preventing heartworm disease is simple. First, choose a heartworm preventive that works well for your pet’s lifestyle and needs, whether a topical liquid applied to the skin, an oral tablet, or a chewable treat. Next, make a note to administer the preventive on time, every time. Finally, schedule your pet’s heartworm test during their annual wellness exam, to ensure they remain disease-free.

With so many heartworm prevention options available, you may have difficulty choosing. Contact our Memorial Villages Animal Hospital team, and we will help you find the parasite prevention product that best suits you and your pet.