The scum has killed dozens of dogs over the years - including at least four in Oregon, three in Wisconsin and one in Minnesota this summer. Wisconsin wildlife experts are warning duck hunters with dogs to be extra cautious this fall. "If the water is pea-soup green, be sure to have clean water along to wash the dog off," Vennie said. "Don't let it drink the water."
Fewer than 100 lakes in Wisconsin typically have some problems with algae bloom each summer and the ones in western Wisconsin causing so much discomfort this year are being fueled by a perfect storm, Vennie said. The last month has seen little rain, warm, sunshiny days and little wind.
The blooms just sit there, growing, then decaying and smelling.
"Some people say they have gotten nauseous and vomited from smelling it," said Ken Schreiber, a Wisconsin Department of Natural Resources water quality specialist.
Officials have banned recreational activities at some lakes in Washington state because of blooms. And in Oregon, the blue-green algae is the number one water quality issue, Carmichael said.
Yet other countries have worse problems, Carmichael said, because many have waters with even more nutrients than exist in U.S. lakes.
In France, a horse died on a beach in July after falling into some decaying algae sludge. Last year, the Chinese government brought in the army to remove the slimy growths so the Olympic sailing competition could be held.
Stephanie Marquis, a spokesman for the Wisconsin Department of Health Services, said her agency had received 41 complaints related to health concerns with blue-green algae so far this season. Rashes, sore throats and eye irritation among the problems, she said.