Summer brings increased risk

Dominic Erickson North Dakota State University

Cyanobacteria, also known as blue-green algae, can produce toxins that are harmful to livestock, wildlife and people. North Dakota State University-Extension specialists have received reports of cyanobacteria blooms in livestock water sources.

Miranda Meehan, North Dakota State University-Extension livestock environmental stewardship specialist, said the growth of that bacteria is facilitated by high temperatures.

“The hot dry conditions ... are perfect for the production of cyanobacteria,” said Meehan.

Additionally the North Dakota Department of Environmental Quality recently reported a cyanobacteria bloom on McDowell Dam. Visit deq.nd.gov/WQ/3_Watershed_Mgmt/8_HABS/Habs.aspx for a list of reported blooms.

Cyanobacteria is caused by an excess of nutrients, particularly nitrogen and phosphorus. Manure and commercial fertilizers are spread to enhance forage and crop production. When those products are misused, either by inappropriate rate or timing of application, the potential for nutrient leaching to surface water is increased. When those nutrients enter surface water, they stimulate growth of cyanobacteria and other microorganisms.

Blue-green algae often occurs in stagnant ponds or dugouts with elevated nutrient levels, forming large colonies that appear as scum on or just below the water surface. Live cyanobacterial blooms can be green, but also red or yellow, and often turn blue after the bloom dies and dries on the surface or shoreline, according to Meehan.

Some species of cyanobacteria can be toxic when livestock and wildlife ingest them. Toxicity is dependent on the species consuming the water, the concentration of the toxin or toxins and the amount of water ingested.

Cyanobacteria can produce neurotoxins and liver toxins. Signs of neurotoxin poisoning can appear within five minutes to up to several hours after ingestion. In animals, symptoms include weakness, staggering, muscle tremors, difficulty in breathing, convulsions and, ultimately, death.

Animals affected by liver toxins may exhibit weakness, pale-colored mucous membranes, mental derangement, bloody diarrhea and may ultimately die. Typically, livestock are found dead before producers observe symptoms. If cyanobacterial poisoning is suspected as the cause of death, producers should check the edges of ponds for dead wildlife.

Jake Galbreath, North Dakota State University-Extension veterinarian and livestock stewardship specialist, advises any farmer or rancher who suspects cyanobacteria poisoning as the cause of a livestock death to contact a veterinarian to conduct a necropsy.

Galbreath said, “A veterinarian can determine which samples would be appropriate for each situation."

When collecting a water sample be sure to wear gloves because cyanobacteria can be toxic to humans. Collect a sample of the suspected cyanobacterial bloom from the surface of the water and deeper in the water. The sample should be kept cool, but not frozen, and submitted to the North Dakota State University Veterinary Diagnostic Laboratory or a commercial laboratory.

The sample can be evaluated microscopically for algae, or the water can be analyzed for several of the toxins at commercial labs at a greater cost.

Galbreath provides some ways farmers and ranchers can prevent cyanobacterial poisoning of livestock.

Unfortunately, unless steps are taken to reduce the nutrient load and minimize the potential for nutrients to enter the water body, there will continue to be a risk for cyanobacterial blooms.

Meehan provides management practices to consider to reduce nutrient loads.