Advisory: Harmful Algae blooms identified in Alcova and Pathfinder Reservoirs

Casper – The Casper-Natrona County Health Department, Wyoming Department of Health, and Wyoming Department of Environmental Quality have issued advisories for Alcova and Pathfinder Reservoirs due to higher than normal levels of cyanobacteria – also known as harmful algae blooms.

Harmful algal blooms (HABs) are dense concentrations of cyanobacteria or blue-green algae that pose a risk to human, pet, and livestock health. Under normal conditions, cyanobacteria are present at low levels and play an important role in aquatic ecosystems. When HABs occur, cyanobacteria become visibly abundant and can look like grass clippings, bluish-green scum or spilled paint on the water surface. Highly visible algae blooms are not unusual occurrences in still waters this time of year, especially when water temperatures have been high.

Cyanobacteria blooms can produce poisons called cyanotoxins and may be associated with other irritants that can cause several health effects in humans, pets, and livestock. Health effects include rashes, itching, numbness, nausea, fatigue, disorientation, abdominal pain, vomiting, and diarrhea.

The following is recommended:

  • Avoid contact with water in the vicinity of the algae bloom, especially in areas where blue-green algae are dense and form scums.
  • Do not drink or consume the water.  Boiling, filtration, and/or cholorination will not remove toxins and will not make the water safe for drinking.
  • Caution should be taken when eating fish, as health effects remain unknown.  Rinse fish with clean water and only eat the fillet portion.
  • Do not breathe water spray in areas of the bloom.
  • Keep pets and livestock away from the water.  Do not allow animals to drink the water, eat dried algae, or groom themselves after contact with the water.
  • In people, pets, and/or livestock come into contact with a bloom, rinse off with clean water as soon as possible.

If a person is experiencing adverse health effects after exposure to an algal bloom, seek medical attention.  Young children, pregnant women, people with weak immune systems are especially at risk.

If pets or livestock experience adverse health effects after exposure to an algal bloom, seek veterinary care. Young animals, pregnant animals, or animals with a weak immune system are especially at risk.

For more information about the health effects of harmful algal blooms, please see the US Centers for Disease Control and Prevention’s website at:

For more information about harmful algal blooms and what is being done in Wyoming about harmful algal blooms, please visit the Wyoming Department of Environmental Quality’s website at:

If you or your pets get sick after using the water, call your doctor, veterinarian or the Wyoming Poison Control Center at 1-800-222-1222.

Waterbodies under an ADVISORY are not closed. For more information, call the Wyoming Department of Health at 307-777-7656.

Click here to download the complete advisory.

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