The evidence is growing steadily that heavy infestations with tapeworms in horses can lead to increased incidence of certain types of colic. For years, tapeworms have been considered a fairly benign parasite to horses because they are rarely found on normal fecal exams that look for parasite eggs. However, recent research shows that the exposure of horses to tapeworms in the United States ranges from 12.7% along the Pacific coast to 95.8% in the upper Midwest. The lowest state was California, with 1.3%, and the highest state was Minnesota with 99.7%