Heartworm disease is one of the major health problems of dogs in the United States and throughout the temperate and tropical areas of the world. As well as being found in dogs and other species, it is now being found in cats in ever increasing numbers. The disease develops when a pet becomes infected with parasites called Dirofilaria immitis that are transmitted through the bite of an infected mosquito.

Heartworms are “foot long” worms that live in the heart and major blood vessels of the lungs. Heartworm disease is spread by mosquitoes to both dogs and cats as well as other animals, such as foxes, coyotes, and wolves, which act as reservoirs and help spread the disease. While dogs can be infected with just a few to hundreds of worms, cats generally have low worm counts. Even one or two heartworms, however, can be life threatening to a cat. While there is a treatment for infected dogs it is time consuming and costly. There is NO treatment approved for cats so prevention is critical. Heartworm infection often leads to severe lung disease and heart failure and can damage other organs in the body as well.

Heartworm infection primarily affects dogs, but infection also occurs in cats. In fact, diagnosis in cats is on the rise. Ferrets, as well as other mammals, such as wolves, coyotes, foxes, and even sea lions, can be infected with heartworms. Outdoor pets are at greatest risk for infection, especially in regions of the world with high mosquito populations. However, even indoor pets become infected by heartworms as infected mosquitoes can, and do, get into houses. In addition, the disease has been found in all 50 states.

Many factors must be considered even if heartworms do not seem to be a problem in your local area. You may travel with your pet to an area where heartworms are more common and not even know it. Heartworm disease is spreading to new regions of the country each year. Stray and neglected dogs and certain wildlife such as coyotes, wolves, and foxes can be carriers of heartworms. Mosquitoes blown great distances by the wind and the relocation of infected pets to previously uninfected areas all contribute to the spread of heartworm disease. This happened following Hurricane Katrina when 250,000 pets, many of them infected with heartworms, were “adopted” and shipped throughout the country! The safest thing to do, and the best insurance against infection, is to administer a year-round heartworm preventive.