For many years we have been fighting a battle against heartworms. We have great products on our side to prevent this disease, but recent findings about heartworm resistance have many pet owners and veterinarians concerned.
Is it possible that heartworms are winning the war?
Heartworm disease has been known to veterinarians for more than 120 years. The heartworms are transmitted from any of more than 70 known species of mosquito, and the disease attacks the pulmonary arteries and right side of the heart in dogs. Heartworms are spread directly to the dog from the mosquito, with no dog-to-dog transmission.
For more than 4 decades, heartworm disease has been effectively prevented in dogs by using available products. But recent research indicates this might be changing. At a veterinary conference in 2010, information was released detailing a genetic mutation in heartworms that appears to confer slight resistance to current preventives. Anecdotal reports in the last 4-5 years also point toward an increase in heartworm prevention product failures in the Mississippi delta region of the U.S.
While lack of efficacy (LOE) to heartworm preventives remains geographically limited, research is ongoing to determine the extent of this problem. Historically, the LOE was attributed to poor owner compliance in the geographic area, the effects of Hurricane Katrina, increased heartworm numbers within the mosquito vector, and/or the increased sensitivity of heartworm testing.
Two prominent veterinary groups, the Companion Animal Parasite Council (CAPC) and American Heartworm Society (AHS) concluded at a recent council strategy session that most credible reports of LOE are geographically limited at this time. In addition, the extent of this problem is not truly known.