Despite the fact that heartworm disease is nearly 100% preventable, many cats are diagnosed with it each year.
WHAT IS HEARTWORM DISEASE?
The infection occurs when an infected mosquito bites a cat’s skin, allowing microscopic heartworm larvae to enter the cat’s bloodstream. Over time these larvae thrive and develop into parasitic worms (heartworms). Although the name of the disease suggests that it mainly affects the heart, the mature parasite eventually resides in the cat’s pulmonary arteries, which carry blood from the heart to the lungs. The scientific name for the heartworm parasite is Dirofilaria immitis. Though cats usually have fewer heartworms than dogs and the worms may not grow as big, the presence of even a few immature worms can cause lung damage. This condition is called heartworm-associated respiratory disease (HARD).
SIGNS OF HEARTWORM DISEASE
The signs of heartworm infection in cats can be confused with signs of many other diseases, including feline asthma. The most common signs include: intermittent vomiting (sometimes of blood as well as of food); diarrhea; rapid and difficult breathing, coughing, and gagging; loss of appetite; lethargy; and weight loss. Some cats with heartworm disease never show any signs, but sometimes the only sign of infection is sudden death.
DIAGNOSIS
Heartworm disease often goes undiagnosed in cats. Diagnosing feline heartworm disease typically involves a complete blood count and blood chemistry profile, chest X-rays, a test to determine whether the patient’s blood contains antibodies to the parasite, and a test to see whether adult heartworm proteins are present in the blood. Ultrasound imaging may be able to show the presence of heartworms in the heart or pulmonary vessels. Unfortunately, these tests can also be inconclusive. Unlike heartworm disease in dogs, there are no good treatment options for heartworm in cats.
The treatment that is regularly used to treat dogs with heartworms is not safe to use in cats, so it is, so it is critically important to prevent the infection in the first place.
TREATING HEARTWORM DISEASE
In some cases, surgical removal of the worms from the heart may be recommended. However, the surgery is costly and carries significant risk. Because there is no good treatment for heartworm disease in cats, your veterinarian will determine how to monitor your pet and manage the symptoms of disease.
PREVENTING HEARTWORM DISEASE
Although heartworm disease is challenging to diagnose and has no approved, effective, or safe treatment, there are highly effective, safe, easy-to-administer preventive medications such as moxidectin, selamectin, milbemycin, and ivermectin. Because mosquitoes can be found indoors, current recommendations are to provide year-round heartworm prevention for all cats. These topical (“spot on”) or oral medications are inexpensive compared to the dangers of the disease for your cat.