Submitted by: Dr. Megan C. Romano, Veterinary Toxicology Resident, University of Kentucky Veterinary Diagnostic Laboratory
Blue-green algae, also called cyanobacteria, are microscopic organisms normally present in aquatic ecosystems, including lakes and ponds. Thousands of species of blue-green algae have been identified; at least 80 are known to produce toxins that can cause illness and death in animals as well as humans. Heavy growth of these toxin-producing algae (“blooms”) can cause high concentrations of toxins in the water. In North America, Anabaena, Aphanizomenon, Oscillatoria, and Microcystis are the species of blue-green algae most commonly associated with poisoning.
In central Kentucky, blooms are most common in late summer and early fall, during hot, sunny weather. Contamination of water with excess nutrients, particularly nitrogen and phosphorus, further encourages algal growth. Common sources of excess nutrients include fertilizer runoff from fields, lawns, and gardens, and direct manure and urine contamination from livestock.
Blooms can produce a blue-green sheen on the water surface, or they can be pea-green and thick, like spilled paint. In addition to blue and green, blooms can also be brown or white. They can form scums, slimes, or mats. It is impossible to tell if a bloom is toxic just by its appearance – ALL blooms should be considered potentially toxic.
Blue-green algae can produce neurotoxins (affecting the nervous system) or hepatotoxins (causing liver damage), and some species can produce both types. Neurotoxins can cause muscle tremors, seizures, excessive salivation, diarrhea, difficulty breathing, and death within hours or even minutes of exposure. Hepatotoxins cause vomiting, diarrhea, bloody or dark stool, and pale or jaundiced (yellow) mucus membranes. Animals can die quickly, or they can develop liver failure over several days.
There are no antidotes for blue-green algae toxins, so early decontamination and supportive care can mean the difference between life and death for an exposed animal. If your pet develops these or any other signs after a recent exposure to water, seek immediate veterinary care. It is important to note that this includes exposure to water with no obvious algal bloom. Toxins can persist in the water for a week or longer after the bloom itself has collapsed.
Preventing blue-green algae poisoning in pets and livestock:
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