Heartworm Disease

Most of us are familiar with Heartworm disease in dogs. This is one of the diseases transmitted by the lovely mosquito. There are many species of mosquitoes that have affinity to spread different diseases, but the important thing here is that mosquitoes transmit Heartworm disease.

Heartworm disease in dogs is easily preventable with administration of monthly preventative or an injection that lasts 6 months. But what about cats?

Cats are not a normal host for heartworms. Additionally, cats have some inherent resistance to the heartworms. A mosquito would have had to feed on a dog prior to feeding on the cat in order to spread the disease. The incidence of heartworm infection in cats is somewhere between 5% and 20% the infection rate for dogs in a given area.

While cats are less likely to be infected, the disease is potentially dire in an infected cat, and there are no clear therapeutic options. Outdoor male cats are most likely to become infected, but nearly one-third of cats diagnosed with heartworm disease at North Carolina State University were strictly indoor cats. Clinical signs can range from asymptomatic (none), to respiratory signs, vomiting (with or without concurrent respiratory signs), neurologic signs, and even death as an initial indicator of disease. Because of the life cycle of heartworms in cats diagnosis of current infection can be difficult.

The question then arises as to whether heartworm preventative is necessary in cats. In 1998, a national study of 2000 largely asymptomatic cats revealed an exposure rate of nearly 12%. This approximates, or exceeds, the rate of infection of Feline Leukemia virus and Feline Immunodeficiency virus. In the Grand Junction area, the rate of feline exposure is probably much lower than the national incidence, but no studies have been done to determine if this supposition is correct.

There are heartworm preventatives available for cats. Two are given orally and two are applied topically on a monthly basis. While the incidence of heartworm disease in cats in the Grand Junction area appears to be low, the results of infection can be devastating and the decision of whether or not to put your cat on heartworm prevention should be made on an individual basis.