U.S. Statistics on Canine Heartworm Disease

100 percent of dogs bitten by an infected mosquito contract heartworm disease.
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Canine heartworms (Dirofilaria immitis) are potentially fatal parasites that infest dogs' cardiovascular and respiratory systems. Infection can be spread by the bite of a single mosquito. Heartworms are a worldwide clinical problem, and in the United States the South historically has the greatest number of cases.

Heartworm History

Despite strides in diagnostics, treatment and prevention since its discovery over 100 years ago, heartworm disease continues to be a significant health risk to dogs in the U.S. American Heartworm Society president Wallace Graham attributes this in part to the influence of changing weather patterns on mosquito populations. The Companion Animal Parasite Council points to pet owners not administering heartworm preventatives correctly as the reason for most heartworm infections in the U.S.

Geographical Distribution

Heartworm infections have been reported in all 50 states, with about 1 in 80 dogs affected, according to CAPC. Infections are most prevalent in moist, humid regions along the Atlantic and Gulf coasts, the southeastern states, the Mississippi River Valley and northern California. Capcvet.org offers detailed information about infections rates by county for both dogs and cats.

Number of Infections & Treatments

According to Pets and Parasites, approximately 300,000 dogs in the United States are diagnosed with heartworm disease every year. With very few side effects, topical moxidectin approved for use in heartworm-positive dogs to eliminate microfilariae. Melarsomine dihydrochloride, also called Immiticide, is the drug of choice for eliminating adult heartworms in dogs.