News Flash


Posted on: July 24, 2020

Perch Lake Test Results

A hand holding two viles of water with a lake in the background.

Perch Lake Test Results Conclude no Harmful Algae

On July 3, a dog became ill after swimming at the public boat landing on Perch Lake. The possibility was suggested that the dog became ill because of blue-green algae. After testing the water and interviewing the dog’s owner and the emergency veterinarian, the Wisconsin Department of Health Services (DHS) concluded that blue-green algae poisoning was not the likely cause of the dog’s illness at Perch Lake.

St. Croix County Public Health collected water samples from the lake and sent them to the Wisconsin State Laboratory of Hygiene. The test results reported that Perch Lake’s water presented a very low risk for toxins from blue-green algae. Additionally, a DHS veterinarian reviewed the case details and concluded that exhaustion or heat stroke could have explained the dog’s symptoms.

We are happy to share that the dog recovered! The emergency veterinarian tested the dog’s blood chemistry and liver and found no damage.

About Blue-Green Algae

Blue-green algae are a normal part of all Wisconsin rivers and lakes. Problems arise if nutrients in the water are elevated, causing them to grow to high numbers also known as a bloom. Blooms are most common during mid to late summer.

Blue-green algae can create toxins that may make both humans and pets sick, if ingested. Blue-green algae poisoning shares similar symptoms with heatstroke and water intoxication. These symptoms include:

  • Vomiting
  • Diarrhea
  • Lethargy
  • loss of coordination

How to Keep You and Your Pets Safe

Here are some tips to stay safe when swimming:

  • Avoid swimming in water that:
    • Looks green like pea soup
    • Is scummy or stagnant
    • Has floating mats
    • Has the appearance of spilled paint (green, blue, white, red, or brown)
  • Always choose the clearest water you can find, especially when small children and dogs are swimming
  • Try to prevent your dog from swallowing too much water. This can cause water intoxication
  • Give your dog frequent breaks from playing in the water
  • Always provide access to shade
  • Provide clean drinking water
  • After swimming, wash yourself and your dog with clean water

Note: Filamentous green algae that is long and stringy, like green hair, and are not dangerous


If you have additional questions, please visit our beach health page. Or you can Learn more about blue-green algae or report a bloom on the Wisconsin DNR’s website.

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