by James J. Galligan, Ph.D., Associate Chair,
Department of Pharmacology and Toxicology

A few weeks ago, I discussed methlymercury contamination of freshwater fish in lakes scattered around the United States.  This topic was of interest because of the local expertise here in Pharmacology and Toxicology on methylmercury induced neurotoxicity.  Well, Michigan State University also has an outstanding research and training program in environmental toxicology (http://cit.msu.edu/) and another news item caught my attention that was highly relevant to the environmental toxicology expertise here at MSU (http://www.google.com/hostednews/ap/article/ALeqM5gqrMC7NvYKe4jGTjLIZM-jRqp-7QD9AVQQK04).

Cyanobacteria in Pool

Cyanobacteria in Pool

Cyanobacteria (blue green algae) blooms are contaminating many freshwater lakes in the U.S.  These algae blooms are unsightly, smelly and potentially deadly, particularly for pets.  Warm dry weather coupled with fertilizer run-off from farms are the main culprits leading to prolific growth of cyanobacteria.  The resulting blue-green sludge piles up on lakeshores and dying and decaying bacteria cause the foul odors.  This ruins the aesthetics of the lakes and certainly reduces the enjoyment for lake front property owners.  However, the real danger comes from the toxins produced by these bacteria.

Cyanobacteria produce two types of toxins: alkaloids and the peptide microcystins.  The alkaloids include saxitoxin, a sodium channel blocker that is a neurotoxin.  Microcystins are small peptides (7 amino acids) and they are predominately liver toxins.  Ingestion of contaminated water results in high levels of microcystin exposure to the intestine and then the liver.  Microcystins are phosphatase inhibitors that disrupt the protein structure of cells in the liver ultimately leading to death of liver cells (hepatocytes) and liver bleeding.  Human poisoning with cyanobacteria-produced toxins is rare because humans (at least most of them) are smart enough not to ingest the foul looking and foul smelling cyanobacteria contaminated water.  However, livestock, or the pet dog may not be so clever or lucky.

The other issue is the wildlife (waterfowl, fish, amphibians) that inhabit the contaminated lakes and who can not avoid exposure to the toxins.  Typically, the algae blooms are short lived and dissipate with rain or a nice breeze.  However, the kill off of the local inhabitants of the lake can far outlast the algae bloom and therefore the effects on the overall health of the lake can also be long lasting.

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