The Minnesota Pollution Control Agency (MPCA) said it cannot positively identify toxic blue-green algae as the cause of two dog poisonings that occurred at Latsch Island late last month. Officials said they do not know what caused the poisonings or suspected poisonings, and while the agency cannot guarantee the safety of water, it advised swimmers and pet owners that if there are no obvious signs of dangerous algae, the water is probably OK.
After swimming at Latsch Island on July 20 and July 30, respectively, two dogs became deathly ill and narrowly survived thanks to emergency veterinary treatment. The dogs' symptoms matched those of animals suffering from blue-green algae poisoning, and at least one Winona veterinarian identified the illness as blue-green algae poisoning.
Local veterinarians reported the incidents to the Minnesota Department of Health (MDH) and MPCA. The reports triggered a response from the agencies to ensure that human health was not at risk, and the agencies followed up by interviewing dog owners and contacting Department of Natural Resources (DNR) officials in Lake City who are familiar with Latsch Island. While the cases triggered suspicions that blue-green algae was the cause, dog owners' description of the scene lacked the typical tell-tale signs of blue-green algae blooms, according to MPCA Research Scientist Steve Heiskary.
"What the vets are saying — those symptoms are really consistent with blue-green algae toxicity; the other information we had, it just didn't stack up right," Heiskary said.
Blue-green algae is common in low levels across Minnesota and in the Mississippi River and naturally produces the toxin microcystin. When stagnant water, warm temperatures, and high nutrient levels cause blue-green algae populations to explode, producing the algal blooms, dangerous toxin levels often follow. In humans, exposure can cause nausea, vomiting, fever, and irritation, according to the Minnesota Department of Health (MDH). Animals can die. There have been numerous confirmed cases of blue-green algae blooms across the state in recent weeks, including metro cities that tested their lakes and a case in Sherburne County confirmed by the MPCA in which a dog died after swimming in a contaminated lake. City officials in Bloomington warned residents that record June rainfalls boosted nutrient runoff and algal blooms in lakes.
Blue-green algae blooms cause water to look like "green paint, pea soup, or floating mats of scum," according to the MCPA. The blooms often produce a foul smell, as well. If pet owners or swimmers see blooms in the water, stay away, the MPCA advised.
The owners of the poisoned dogs said that their dogs were swimming at Latsch Beach and that there were no visible algae blooms or offensive odors. Blue-green algae blooms can occur in backwaters and there might be sheltered eddies or puddles on the island that contained the algae, but Heiskary and his colleagues agreed that the main channel of the Mississippi River at Latsch Beach is an unlikely place for the toxic algae to occur.
"When we take this picture in total, we have no environmental tests of what the conditions were like; it's just these observations and the conversations that were held," Heiskary said, referring to interviews with dog owners last week. "We cannot say for sure that [blue-green algae] was the cause. It would be a possibility, but we don't have enough information to close the loop on that. What else it could be, I don't know."
"It's a puzzle," said Dr. Lehua Maloney of Winona Veterinary Hospital who treated one of the dogs. The presence of blue-green algae at Latsch Beach was unlikely, she agreed, but it might have bee growing in a puddle on the island.
When asked if Maloney's theory that the dogs consumed algae in puddles elsewhere on the island was possible, Heiskary said it was. "It's possible we were looking at the wrong place," he added. However, in interviews with state officials, dog owners' reported that their dogs were in river at the beach and did not wander off elsewhere.
Mahoney added that a local specialist in veterinary internal medicine was also skeptical of the possibility of blue-green algae poisoning. What else could it be? "The only thing I can think of would be anaphylactic shock," Maloney said, referring to a life-threatening allergic reactions to a bee sting or other allergen. Perhaps someone left rat or mouse poison out by their boathouse and the dogs got into that, she speculated. "Probably the weirdest thing is that there were two dogs, and two dogs having the same symptoms in the same location," she said. That made her believe poisoning seems more likely than coincidental allergic reactions, she added. "It's a mystery. We'll probably never know," Maloney said. Still, blue-green algae is on her list of potential causes.
Heiskary concluded by echoing the MPCA standard warning to be cautious of blooms. "If things look at all suspect, don't [swim], but if things look fine, I can't give any guarantee, but that general rule of thumb should be [it's] fine," he said.