Dogs, Humans Should Avoid Warm Lakes to Dodge Pythiosis

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, says 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 says.

“Lined ponds should be OK, because the pathogen is probably soilborne,” she says. “I believe that dogs who do not swim have also gotten it though, possibly from eating infested grass. Dogs that drink infested water can get intestinal infections.”

The pathogen can also cause skin infections in people, dogs and horses.

Pythium insidiosum, a pathogen that sickens some animals, has been reported in veterinary cases throughout the Southeast. Goss and master’s student Jackson Presser in the UF/IFAS School of Natural Resources and the Environment, studied 19 lakes or ponds in North Florida. They found 11 of them have Pythium insidiosum, and their study is published in the journal Medical Mycology. Additionally – though not a part of this published study -- they sampled 25 lakes in Central Florida over this past summer and found the pathogen in all of them, Goss says.

“We don’t know if this pathogen has been here a long time or if it came from the tropics,” Goss adds. “The genetic variation we report suggests it may be both -- local genotypes and others brought in one way or another.”

Goss also says scientists aren’t sure why so few humans have contracted pythiosis in the United States, as opposed to animals. People with the blood disorder thalassemia seem to be more susceptible to infection in Thailand. “Agricultural workers in flooded rice fields may be exposed to the pathogen for long periods of time and perhaps don’t have the opportunity to bathe with soap that would wash the spores off the skin."

Source: University of Florida Institute of Food and Agricultural Sciences