County Agent Update

Cyanobacterial Poisoning in Livestock

Toxic Cyanobacterial blooms, blue-green algae, occur because of favorable conditions in stagnant waters. Those conditions include hot, sunny days and warm, nutrient rich water. These blooms occur late summer into early fall. With the favorable conditions listed above, the bacterial blooms can multiply rapidly. Recently the North Dakota Department of Health listed Cottonwood Lake in Williams County with a warning that a bloom has taken over a significant portion of the lake. The bacterial levels present are exceeding the public health criteria. These blooms usually do not last long. Rain, heavy winds or cooler temperatures often break up the bloom, mixing the bacteria into the water body within a few days. However, if the favorable conditions continue, these blooms can last several weeks. While the bloom is present, you will see large colonies of the bacteria that appears as scum on or just below the water’s surface. Live cyanobacteria is green and turns blue after it dies and dries on the surface of the shoreline. Concentrations of the bacteria often are bluish green but may vary from dark green to brownish green, depending on the population. The formation of a toxic bloom is unpredictable.

Signs of neurotoxin poisoning usually appear within 20 minutes of the animal ingesting the water. Symptoms include weakness, staggering, difficulty in breathing, convulsions and ultimately, death. Animals that are affected by liver toxins may exhibit weakness, pale-colored mucous membranes, mental derangement, bloody diarrhea and ultimately, death. Typically, livestock are found dead before producers observe symptoms. Livestock that do survive the cyanobacterial poisoning may lose weight and in some cases will develop photosensitivity, which will cause sunburns which will peel and expose fresh, new skin. No known antidote is available for poisoning from cyanobacteria. The best solution is to be aware of conditions that spawn cyanobacterial blooms. The toxicity is dependent of the species consuming the water, the concentration and the amount of water ingested. Ingestion of approximately one quart of heavily contaminated water has been fatal to cattle. These concentrations that are lethal to livestock usually do not occur on small water bodies that do not have enough wave action to concentrate the bacteria on shore. There are at least four types of potentially poisonous cyanobacteria known to occur in North Dakota. However, not all cyanobacteria are poisonous, the cyanobacteria that generate poisonous toxins do not always do so. The toxins from these bacteria, termed cyanotoxins, are poisonous to nearly all livestock and wildlife, including cattle, horses, sheep, pigs, chickens, ducks, pigeons, geese, herons, songbirds, dogs, rabbits, small wild and domestic animals, and even frogs, fish and snakes. For this information and more, please refer to the NDSU Extension Service publication Cyanobacteria Poisoning, revised by Miranda A. Meehan and Michelle Mostrom. The Williams County Extension office has copies available, 701-577-4595.