Blue Green Algae Poisoning

[Guest guest]

Blue Green Algae

(Cyanobacteria) Poisoning

By Regg Neiger, SDSU

http://vetsci.sdstate.edu/xnews/ahm03-2.html

Common organisms in South Dakota surface water that cause Blue Green Algae toxicosis include; Anabaena flos-aque, Aphanizomenon flos-aque, Microcystis aeruginosa, and Oscillatoria agardhii. Normally there are large populations of these organisms in the summer and they die off in the winter. However, their presence under normal situations does not mean a poisoning will occur. Blue green algae only produce toxins under specific conditions. Before they die off for the winter they produce resting forms of algae called akinetes that settle to the bottom of the body of water and are inactive till water warms up in the spring.

Toxic blooms usually occur when the weather is sunny and warm and the water is stagnant and high in nutrients (esp. phosphates). Blue green algae will float to the surface of the water and form what is called a bloom. Then the wind will usually blow the floating algae to shore, which further concentrates the organisms. These algae are normally green but turn a light blue-green when they die and form the bloom.

Animals of all types are susceptible to poisoning when drinking water from a bloom. Blue green algae produce a variety of toxins. Exposed animals can die in 24 hours or less. Sometimes they die within minutes. There are three main syndromes produced, two which are caused by effects on the nervous system and one due to liver damage. The clinical signs seen when neurotoxins are involved include rigidity, tremors, paralysis, cyanosis, and death due to respiration paralysis. When the neurotoxin called anatoxin-a(s) is involved there is cholinesterase inhibition, and signs can include increased salivation, gastrointestinal motility, diarrhea, urination, and ocular discharge.

Hepatotoxins and related toxins cause a clinical picture with gastrointestinal disturbances characterized by vomiting depending on the species of animal poisoned, abdominal pain, and diarrhea that may be bloody. Then the animals get weak, pale, lethargic, and die usually within 24 hours. Survivors of the hepatotoxins may become photosensitized due to liver damage. These animals get easily sunburned on skin with white hair or hairless areas.

When examining an animal suspected of algae poisoning look for blue-green staining of hair and skin. Blue-green algae may be seen in the gastrointestinal tract. Lesions vary from none to gastrointestinal disturbance. When liver toxins are involved the liver may be swollen and hemorrhagic.

A diagnosis is based on the history, clinical signs, pathological findings, and identification of toxic blue-green algae in the water. When collecting water for examination, take a sample with large amounts of the algae present. A water sample needs to be taken as soon as possible because if the wind changes the algae may be dispersed as fast as they appeared. Send to the diagnostic laboratory 5 ml of water chilled, 5 ml of water in equal amounts of 10 % formalin, and a gallon of water frozen.

Do a complete necropsy and submit appropriate samples to diagnostic laboratory to rule out other causes of death.

Diagnosis, treatment, and prevention are frustrating because the blooms can develop suddenly and disappear just as fast. The main thing that can be done is to remove remaining animals from source of the toxic algae. The course of the poisoning is so rapid you may not have the chance to treat the animal. No specific antidotes are available except if you think that anatoxin-a(s) is involved (the cholinesterase inhibitor) then atropine may be effective. However remember in horses that atropine can cause severe intestinal stasis and associated colic. If time permits, measures to evacuate the gastrointestinal tract, bind the toxin (activated charcoal), maintain respiration, and supportive care are indicated.