Recently, a of a pair of dogs died from suspected cyanobacteria poisoning from a lake near Laramie. In the wake of this and other reports from around the country, the Wyoming Department of Environmental Quality (DEQ), the Wyoming Department of Health (WDH) and the Wyoming Livestock Board (WLB) have been getting a lot of questions about harmful cyanobacterial blooms (HCBs) in Wyoming waters. Here is what they want you to know.

Cyanobacteria, also known as blue-green algae, can form blooms that produce toxins and other irritants that pose a risk to human, pet and livestock health. HCBs typically occur in still or slow-moving water during the hotter months of summer. They happen occasionally and at irregular intervals. The blooms can last for a few hours or a number of months.

When there is a bloom, the cyanobacteria can look like grass clippings, blue-green scum, or spilled paint on the water surface. HCBs may also be suspended in the water column, so HCBs may also make the water appear green or blue-green. To see pictures of harmful cyanobacterial blooms found in Wyoming, click here.

Courtesy Wyoming Department of Environmental Quality
Courtesy Wyoming Department of Environmental Quality

If an HCB is present, the WDH and WLB recommend the following:

  • Avoid contact with water in the vicinity of the bloom, especially in areas where cyanobacteria are dense and form scum.

  • Do not ingest water from the bloom. Boiling, filtration and/or other treatments will not remove toxins.

  • Rinse fish with clean water and eat only the fillet portion.

  • Avoid water spray from the bloom.

  • Do not allow pets or livestock to drink water near the bloom, eat bloom material or lick fur after contact.

  • If people, pets or livestock come into contact with a bloom, rinse off with clean water as soon as possible.

Seek medical attention or a veterinarian if a person or animal is experiencing adverse health effects after exposure to a cyanobacterial bloom. Young children, pregnant women, people with weak immune systems and animals are especially at risk.

The Wyoming Department of Health issues a recreational use advisory for lakes and other publicly accessible bodies of water when harmful levels of cyanobacteria and/or toxins are present in the water.

You are encouraged to check for current recreational use advisories here: if you want to know where HCBs may be occurring.

The Wyoming Department of Environmental Quality has a hotline that the public can use to report suspected HCBs in bodies of water that are accessible to the public at (307) 777-7501 or submitting a complaint online at

If you are a private landowner who needs to test for HCBs, the Department of Health encourages you to review Wyoming’s HCB Action Plan for more information on simple tests and analytical services.

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