Mystery in the bay

Pfiesteria: Caution, not panic, called for as scientists study the possibility of another outbreak.

August 22, 1999

THREE SUSPECTED cases of poisoning by the microorganism Pfiesteria piscicida on the Lower Shore are no cause for panic. Careful monitoring of the implicated Chesapeake waters and scrupulous medical examination of victims are needed to determine the facts.

The symptoms reported by three persons from contact with a tributary of the Manokin River -- skin irritation and flu-like illness -- are similar to those of Pfiesteria poisoning. But these are broad-spectrum ailments that might have any number of causes.

Yes, the single-cell Pfiesteria organism is present in Maryland waters, and probably has been for many years. But the creature is seldom toxic to humans or fish as it goes through more than 20 different stages in its life cycle. Only under certain conditions (still being studied by scientists) does it turn harmful.

That happened in 1997 -- a dry, hot summer like this one -- in sluggish streams of the Eastern Shore that saw significant algae blooms linked to human pollution. The results were fish kills, unexplained illness of watermen and naturalists and the closing of three waterways as health hazards.

As state officials point out, Pfiesteria toxins have not been confirmed this year in the Back Creek tributary of the Manokin. The state says the incidence appears limited to a small, remote stretch of water, even while urging public caution in fishing and recreation on the creek.

Officials also note that no fish kills or fish lesions -- the initial signals of 1997's problem -- have been seen there. High concentrations of the organism in water samples does not mean the microbe is in the toxic stage.

But the Manokin River system was a source of the toxic outbreak two years ago. And there's no reason to doubt that it could erupt again. Caution is warranted.

Maryland continues to regularly monitor streams and rivers that experts believe are most susceptible to toxic Pfiesteria outbreaks. State medical studies of the problem provide a valuable basis for informed response.

In the long term, cleaning up the bay's waters will help to reduce the threat of Pfiesteria on a broad front. Curbing surface runoff pollution from farms and other sources remains a key to combating the so-called "cell from hell."

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