The Wyoming Department of Health recently issued an advisory for Leazenby Lake south of Laramie. Cyanobacterial blooms were located at the lake after the death of two dogs that ingested the lake water.

The blooms, commonly known as algal blooms throughout the United States, have been termed harmful cyanobacterial blooms (HCBs) by the Wyoming Department of Health.

“It’s actually a bacteria,” State Public Health Veterinarian Karl Musgrave said. Though the blooms are often called “algal,” they are not an algae.

“Cyanobacteria are distinct from algae because they are prokaryotes rather than eukaryotes. They are similar to algae in that they are photosynthetic and can produce their own energy from sunlight,” Watershed Protection Surface Water Quality Standards Coordinator Lindsay Patterson said.

The normal peak season for HCBs is approaching. Natural Resource Analyst Michael Thomas said the blooms are most prominent in Wyoming in late August, early September.

How HCBs show up

HCBs are common in eastern states, Musgrave explained, but have been a more recent concern in Wyoming. However, they could have been here a while without anyone noticing.

“Cyanobacteria is a normal component of your lake phytoplankton community, but they’re usually there in very small numbers,” Thomas said. Cyanobacteria are a type of microbe and play an important role in nitrogen cycling.

“Some species of cyanobacteria can even fix nitrogen from the atmosphere, meaning they can take up nitrogen gas from the atmosphere and convert it into usable forms,” Patterson said.

“When these blooms occur, it’s when the cyanobacteria become disproportionately abundant, and this is due to the right conditions,” Thomas continued.

Thomas explained the right conditions to be excess nutrients in the water, warmer water temperatures and slower moving water. The excess nutrients, or nutrient pollution, that perpetuate HCBs are nitrogen and phosphorous. Under these conditions, the cyanobacteria can multiply, forming blooms.

“Some of the major sources of nutrients come from waste water treatment plants and agricultural run-off when you’re applying fertilizers to lawns or to agricultural fields. Phosphorous often comes from sediment. It’s bound to sediments so can wash into water bodies from agricultural practices,” Patterson said.

Patterson explained storm water to be a source of nutrients as well. A nitrogen compound from fossil fuel burning power plants could be released into the atmosphere then fall with a rainstorm. This process is called atmospheric deposition.

Other sources of excess nutrients could be septic systems, lawn care products such as fertilizer, and animal and pet waste that run off into the lake.

What HCBs do

Evidence of HCBs appears as blue-green algae on the surface of the water. While the cyanobacteria itself can be an irritant to the skin, potentially causing rashes, it is not the most harmful part of HCBs.

“Internally they produce toxins and they can release some into the environment, and then also when they senesce or die, they can release the toxins they have internally,” Thomas said.

“The bacteria produces a toxin, and it’s actually the toxin that does the damage,” Musgrave said. The toxins produced are called cyanotoxins, and different cyanotoxins come from different types of cyanobacteria.

“There’s toxins that produce damage to your kidney, there’s toxins that produce damage to your liver, there’s toxins that damage your nerves,” Musgrave explained. “It just depends on which of those toxins a dog or a person gets that will produce different symptoms.”

“This is more of a poisoning,” Musgrave said. He explained poison control centers get involved because the toxins act as poison.

“People being poisoned is actually pretty rare, and it’s just because they don’t typically ingest the water,” Musgrave said.

Among the types of cyanobacteria, phormidium is the one identified in Leazenby Lake. Phormidium produces the cyanotoxin anatoxin-a. Anatoxin-a affects the functioning of the central nervous system by attacking the nerve cells. Many mechanisms in the body are controlled by nerves, including breathing.

In the most severe case of anatoxin-a poisoning, the toxin renders the nerve cells incapable of performing correctly and respiratory paralysis takes place. Musgrave said the symptoms of the dogs that died after swimming in Leazenby were respiratory paralysis and death.

“The symptoms the dogs were exhibiting prior to passing, staggering and labored breathing, is consistent with exposure to anatoxin-a, but again, we cannot definitively link the dog deaths to the bloom or toxins since a necropsy was not conducted,” Thomas said.

It is hard to confirm the relation of HCBs to the death of dogs or even a rash on a human. There are currently no tests to determine if an animal or human has been affected by an HCB.

“We don’t really know for sure about these dogs, I mean they died before any testing could be done, if it could be done,” Musgrave said. The dogs died three to five hours after being in the lake.

Despite the difficulty in confirming a link between HCBs and animal death, Patterson said some dogs’ deaths in Florida have been directly linked to HCBs in the St. Lucie River.

“I think that’s where sometimes it can be bad for pets and animals, because they might consume more of it, you know, than even people would just out there swimming and stuff,” Patterson said. Because dogs swim in the water and may ingest the water, they tend to be at more of a risk.

There are currently no human deaths definitively linked to HCBs, “but that’s not to say there hasn’t been illnesses or anything like that,” Thomas said.

More to be understood

“There’s not a good relationship usually between the density of cyanobacteria and the toxin concentration,” Thomas explained more cyanobacteria does not necessarily mean more toxins.

Toxin-production of HCBs is yet to be fully understood.

The time of sampling plays a critical part, Thomas explained. “These things are really dynamic. They can move quickly, they can dissipate, reappear quickly, and when you sample them they may not be producing toxins at that time but maybe if you came back an hour later they might be producing toxins.”

“We’re managing on the fact that if they’re [HCBs] present they could potentially produce toxins, or if you come into contact with really dense blooms it could make you have a rash,” Patterson said.

The advisory on Leazenby Lake is still in effect. As for when the advisory will end, Thomas said, “We typically base it on whenever the bloom fully dissipates.”

Patterson said the blooms die out when the weather begins to cool down because the bacteria thrive in warmer environments. Wind also dissipates the bloom. Water movement in general can prevent the forming of blooms since, in addition to warmth, the bacteria thrive in still water.

What to do

To do your part in keeping HCBs from forming, do not over-fertilize, pick up pet waste and maintain your septic system.

The advisory for Leazenby Lake included some information on how to keep yourself and your pets protected from HCBs. Avoid contact with water that has evidence of an HCB, such as blue-green scum on the top of the water.

Do not ingest the water. Boiling and filtration will not remove the toxins. Only eat the fillet portion of fish from a lake with HCBs. If you, your livestock or your pet have contact with a bloom, rinse off with clean water as soon as possible and contact your doctor or veterinarian.

If you see evidence of HCBs, report it at or call (307) 777-7501.

“Once we receive the report, we will check the satellite imagery to confirm cyanobacteria presence, if available, then ask the water management agency to check conditions, and send personnel out there to collect samples,” Thomas said.

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