Pfiesteria has been ruled out as the cause of rashes on two environmental workers a week ago, but a third case remained under investigation yesterday and state officials urged people around the Manokin River in Somerset County to remain wary of the toxic microbe.
Maryland Department of Natural Resources officials were optimistic after periodic weekend checks of the area around Back Creek, a tributary of the Manokin, turned up no fish kills or other signs of Pfiesteria. Two years ago, the toxin killed more than 30,000 fish and sickened 13 people in Maryland.
"Every once in while you see a fish with a mark on it, but no indication of Pfiesteria," said John Surrick, a department spokesman. "It's like if you look at a group of kindergarten children, you will will probably see a scraped knee or two but no trend."
On Friday, health officials determined that Pfiesteria was not to blame for rashes and flu-like symptoms that suddenly struck the two environmental workers who were in the area.
Results of the Pfiesteria tests conducted on a third man, a recreational waterman who was on Back Creek on Aug. 9, are expected in the middle of this week, said Robert Venezia, director of health coordination for the state health department.
Until those results are in, as well as conclusive findings from water analysis, Gov. Parris N. Glendening has issued a warning for danger to fishermen and boaters, but did not order the creek closed to recreational use.
Pfiesteria is believed to exist widely in a nontoxic form in the Chesapeake Bay and its estuaries, but for unknown reasons it can change form and begin attacking fish by emitting powerful poisons.
Preliminary water tests revealed signs of Pfiesteria, but will not show if it is toxic until later this week, Surrick said.