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Experts remind public to avoid HCBs in Wyoming water sources

by Wyoming Livestock Roundup

As summer temperatures rise and residents head to local waters to cool off and relax with friends and family, the Wyoming Department of Environmental Quality (WDEQ) and other state officials want to remind the public to avoid harmful cyanobacterial blooms (HCBs), report suspected blooms to WDEQ and report bloom-related illnesses to the Wyoming Department of Health. 

The Wyoming Livestock Board also reminds the public to protect pets and animals from HCBs by reducing exposure, identifying symptoms and reporting any HCB-related illnesses.  

What are HCBs?

According to the WDEQ website, cyanobacteria, commonly known as blue-green algae, can form HCBs, which are dense concentrations of cyanobacteria that produce toxins and irritants and pose a health risk to humans and animals. 

HCBs are episodic and can last for a few hours or several months.

Wyoming State Veterinary Laboratory (WSVL) Director Dr. Will Laegreid stated, “HCBs normally develop when water temperatures increase in still or slow-moving water such as rivers, lakes and reservoirs or when wind aggregates HCBs near shorelines. HCBs can vary in color from blue-green to brown and even red.”  

“Cyanobacteria will resemble spilled paint on the surface of the water, giving the water a translucent appearance or appear as floating clumps of grass, scum or green water, mostly occurring in late summer and early fall,” he added.

Laegreid further explained cyanobacteria produce neuro and liver toxins, which are poisonous to nearly all livestock, wildlife and domestic animals, and there is no antidote for blue-green algae poisoning. 

If a bloom is present, avoid contact with the water, do not ingest the water and if individuals, pets or livestock come into contact with the bloom, rinse off with clean water immediately. 

Protecting pets and livestock

It can rapidly become fatal when animals are exposed to or digest cyanotoxins from algae blooms. 

Laegreid stated, “Animals can be exposed to toxins by eating bloom material, drinking or swimming in water with HCBs or licking their fur after contact with the bloom.” 

Typically, livestock poisonings occur when wind blows the dying bloom into a concentrated mass to the shoreline where cattle drink.

Research from South Dakota State University reported, due to the rapid advancement of death, the observation of clinical signs including tremors, paralysis, respiratory failure and diarrhea, are not often seen. 

The most frequent indicator of toxicity from blue-green algae is finding a dead animal close to contaminated water.

“Symptoms in animals could appear minutes to days after exposure, and if an animal appears sick after contact with HCBs, immediately rinse them off with clean water and seek veterinary care,” Laegreid added.

If the death of an animal is suspected to be caused by exposure to blue-green algae toxicity, a water source inspection would be conducted and the edges of the water source would be checked for other deceased animals. 

In addition, a local veterinarian would need to be contacted to collect appropriate samples to confirm or deny the blue-green algae toxicity and have the water tested. 

Laegreid said, “Preventing exposure is the most effective way to avoid this deadly toxin.” 

According to North Dakota State University Extension, producers can reduce livestock exposure by reducing nutrient levels entering the water source, fencing off ponds, utilizing other water sources following dry, hot weather and adding copper sulfate to the water supply if the water has a history of algae bloom. 

Predicting HCB activity 

WDEQ is collaborating with researchers at UW’s Department of Zoology and Physiology to better predict and manage HCBs within the state. 

WDEQ HCB Coordinator Kelsee Hurshman stated, “WDEQ does not have an indication about whether HCBs may be worse this year than in other years, as HCBs thrive in warm temperatures and sunlight.”

“With cooler temperatures this spring, blooms may form a little later in the season at some waterbodies than they did last year,” she added. “Last year, bloom advisories were issued for two waterbodies with high densities of cyanobacteria by the end of June.”

Hurshman continued, “It is almost July, and no advisories have been issued yet this year. But, WDEQ expects to begin receiving reports and finding HCBs soon and will begin routine monthly monitoring for cyanobacteria and cyanotoxins at high recreation locations of 25 prioritized waterbodies in mid-July.” 

This research will help inform the effectiveness of satellite imagery to identify and quantify HCBs, help identify environmental conditions leading to HCBs and identify management methods to prevent future HCBs. 

Melissa Anderson is the editor of the Wyoming Livestock Roundup. Send comments on this article to

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