Cyanobacteria

Chapter 41 Cyanobacteria



Stephen B. Hooser, DVM, PhD, Patricia A. Talcott, MS, DVM, PhD





• Blue-green algae blooms tend to occur in stagnant, eutrophic bodies of water when environmental temperatures are warm and the weather is calm.

• Pets are at risk when the blooms become concentrated along the shoreline or edge of the water by wind and water movement.

• Microcystis spp. and Nodularia spp. can produce hepatotoxic blooms; Anabaena spp., Aphanizomenon spp., Lyngbya spp., and Oscillatoria spp. can produce neurotoxins.

• Clinical signs following oral exposure to the hepatotoxins microcystin or nodularin are related to liver damage and include lethargy, vomiting, diarrhea, depression, weakness, pallor, shock, and death.

• Clinical signs following oral exposure to the neurotoxins anatoxin-a and anatoxin-a(s) often occur very rapidly after exposure and include salivation, lacrimation, urination, and defecation (SLUD), muscle rigidity, tremors, seizures, paralysis, respiratory paralysis, and death.

• Treatment is primarily supportive.

• Confirmation of exposure can include detection of the algae in stomach contents or suspect water source and detection of the toxins in stomach contents or liver.


SOURCES


Blue-green algae (cyanobacteria) are commonly found growing in fresh and salt water in temperate areas worldwide. In the United States, they often are found in freshwater ponds, lakes, rivers, streams, canals, and ditches. Under appropriate climatic and nutritional conditions, very rapid growth of blue-green algae results in “blooms” that rise and accumulate at the surface of the water and sometimes produce hepatotoxins and/or neurotoxins. A single bloom can consist of more than one type of cyanobacteria. Blooms of blue-green algae in the northern United States often occur from late summer to early winter (although they can occur anytime throughout the year) and are commonly associated with periods of hot, calm weather, decreased rainfall, increased nutrients (e.g., nitrate, phosphate, sulphate) in the water, and with winds that blow and concentrate the algae along the shore. Blooms can occur all year long in southern states when all the environmental and nutritional conditions are met.



TOXIC DOSE


The blue-green algae Microcystis and Nodularia can produce the cyclic peptide hepatotoxins microcystin and nodularin, and Anabaena, Aphanizomenon, Lyngbya, and Oscillatoria can produce the neurotoxins anatoxin-a and anatoxin-a(s). It has been difficult to calculate what a “toxic-lethal” dose is for dogs and cats; the number of cyanobacteria and concentrations of toxins vary considerably among blooms. However, based on case reports, toxicities and lethalities have been observed in dogs following single exposures to contaminated water through drinking or consuming water while swimming.



MECHANISM OF TOXICITY


Toxicoses have been reported in dogs following ingestion of water containing blue-green algae. Cats appear to be less commonly affected, even though all species are considered to be susceptible to the effects of the toxins. Not all blue-green algae blooms produce toxins, and the specific water conditions that support toxin development have not been firmly established. The hepatotoxins microcystin and nodularin are rapidly absorbed from the intestine following ingestion and are subsequently taken up by hepatocytes via a specific carrier-mediated uptake mechanism. There they inhibit protein phosphatases, which initiate a cascade of events leading to a rapid, massive hepatocyte necrosis, intrahepatic hemorrhage, and shock.


The neurotoxin anatoxin-a is a potent postsynaptic depolarizing neuromuscular blocking agent, whereas anatoxin-a(s) is a potent acetylcholinesterase inhibitor. Both compounds are rapidly absorbed from the small intestine following ingestion.

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  4. Grapes and Raisins

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Sep 11, 2016 | Posted by in SMALL ANIMAL | Comments Off on Cyanobacteria

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