Detroit Free Press
CDC: Toxic blue-green algae is infecting humans, animals in Michigan summers
Mika Travis, Detroit Free Press – July 21, 2023
Harmful algae blooms in Michigan and other states are spiking during the summer in freshwater bodies such as lakes, according to a recent CDC report.
Harmful algae blooms are often caused by a rapid growth of cyanobacteria, known as blue-green algae, a naturally occurring bacteria. Gary Kohlhepp, Lake Michigan unit supervisor of the Michigan Department of Environment, Great Lakes, and Energy, said that a small amount of cyanobacteria is a safe and natural part of the water system, but it can become toxic when it begins to cluster in large quantities and creates blooms. Toxins produced in these blooms can lead to illness in humans and animals.
According to the National Oceanic and Atmospheric Administration, blue-green algae blooms are a common occurrence in the Great Lakes, specifically Lake Erie.
CDC report results
The CDC report collected voluntary data from public health agencies across 16 states on harmful algae bloom events in 2021, referred to as harmful algal blooms in the report. Here were the findings:
- Most reported events occurred during the summer, with a peak in August (25% of reported events).
- Most of the events (90%) reported were in lakes, reservoirs or other freshwater bodies.
- A third of the reports of human illness occurred in June.
- The most common symptoms in humans were gastrointestinal, generalized (headaches and fevers, for example), and dermatologic.
- Reports of animal illnesses occurred primarily in August (86%), mostly involving wildlife.
- The most common symptoms in domestic pets were gastrointestinal, such as vomiting, and generalized, such as lethargy.
- A harmful algae bloom event in Washington killed 2,000 bats.
- There were 368 harmful algae bloom events reported, resulting in 117 human cases of illness and at least 2,715 animal cases of illness. (Animal cases are underrepresented because some group animal reports did not provide the number of total animals impacted, or indicated that the number they gave was an underestimate.)
Kohlhepp said that EGLE had seen an increase in reporting on harmful algae blooms, though that may not indicate an actual increase in the quantity of blooms in the state.
“I think some of that increase is just that people are more aware of it and more likely to report it,” he said.
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Spotting harmful algae blooms
These harmful algae blooms can appear as accumulations of algae that coat the surface of the water or as a neon green color in the water.
Kohlhepp said that if there aren’t any visible signs of a harmful algae bloom in the water, there’s a good chance it’s safe, though the only certain way to tell whether a body of water is toxic is by testing.
In one instance, Kohlhepp’s team tested a clear spot in a lake that had a harmful algae bloom in another part of it. In the spot that appeared clear, there was only a miniscule amount of cyanobacteria picked up.
“The good news is, generally, if you don’t see a bloom, the toxins are not present,” Kohlhepp said. “There’s almost always an indication that there’s something going on when the toxins are present, either that bright color or the surface accumulation.”
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Symptoms of exposure
According to Michigan Sea Grant, the most common type of blue-green algae in the Great Lakes is microcystis, a bacteria which produces a liver toxin and skin irritant.
When exposed to these harmful algae blooms, humans often develop a rash. Other possible symptoms include nausea, headache and fever.
Animals, such as dogs, who experience symptoms may appear sluggish. Other symptoms found in animals include vomiting and dark urine.
Steps to take after exposure
Because humans usually experience dermatologic symptoms, Kohlhepp recommends washing off as soon as possible after coming in contact with a harmful algae bloom. If they notice symptoms, they should visit a doctor for next steps.
Dogs and other animals should also be rinsed off after exposure, though symptoms may still arise if they ingested the algae-filled water. Pet owners should watch for symptoms and take them to a veterinarian if they notice any symptoms.
How to report a harmful algae bloom
EGLE collects reports of harmful algae blooms through email at algaebloom@michigan.gov. They recommend sending a photo alongside the report, so that they can more easily identify algae blooms and send someone to test the water.