CAPC’s role in heartworm prevalence tracking and guidance


This independent organization is at the forefront of heartworm disease monitoring.

cat and dog

Michael Pettigrew /

The Companion Animal Parasite Council (CAPC) has served as a timely, credible and accurate provider of information about the prevalence, diagnosis, treatment, prevention and control of parasitic infections since 2002. As an independent, nonprofit organization dedicated to increasing awareness of the threat parasites present to both people and pets, CAPC is an excellent resource for both pet owners ( and veterinary professionals ( alike.

CAPC’s parasite forecasts, prevalence maps and guidelines are all designed to keep veterinary professionals and pet owners informed about the growing risk parasites pose in the United States.


Recent prevalence data show that dogs and cats in all 50 states are susceptible to heartworm infection. While prevention in dogs is considered commonplace, heartworm frequently goes undiagnosed in cats because they tend to be asymptomatic.

Heartworm infections continue to increase in number and geographic distribution throughout the U.S., with the largest numbers of cases located in the Southeast and the Mississippi River Valley. An apparent high level of prevalence has been documented in northern California.

For canine heartworm cases to be included on the CAPC prevalence map, the antigen test used for diagnosis must have a minimum sensitivity and specificity of 90%, and be approved by the U.S. Department of Agriculture. Because the sensitivity of some heartworm antigen tests decreases at lower worm burdens, the 90% sensitivity requirement applies only when three or more adult female worms are present.

The forecast for 2020 has indicated an increase in the prevalence and incidence of heartworm in both dogs and cats.


Like the American Heartworm Society, CAPC recommends annual testing of all dogs for both antigen and microfilariae of heartworm. As soon after diagnosis as is medically practical, infected dogs should be treated with labeled adulticides and microfilaricides (if microfilaria is present). And all dogs should be protected from heartworm infection with the use of year-round preventives.

For cats, CAPC also recommends antigen or antibody testing for heartworm prior to starting them on a preventive, which should be used year round. Unlike dogs, annual testing for cats is not discussed. Maintaining infected cats on preventives to protect them from acquiring additional heartworms, closely monitoring their health status and providing symptomatic care as needed are advised.

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