University of Florida scientists warn against letting your dog swim in warm water bodies after they found several lakes with a pathogen that can make canines sick. Animals, including dogs and horses, can contract pythiosis from swimming spores, said Erica Goss, a UF/IFAS assistant professor of plant pathology. About 10 cases of humans getting sick from this disease have also been reported in the U.S. In addition to keeping their animals out of lakes, people should avoid ponds and other standing water that contains grass and aquatic vegetation, particularly in the hot months, Goss said.