WASHINGTON – Human ailments associated with long-term exposure to pfiesteria-infested waters seem to disappear within six months, according to new studies by University of Maryland and Johns Hopkins University researchers.
Neurological exams of 19 people who had been exposed to the toxic micro-organism for at least six hours per week showed that they tested well below average in memory and learning tests.
The subjects, mostly commercial fishermen, might not be able to remember where they were supposed to be going when they were driving or they might forget equipment needed for fishing.
But three months after the initial exposure, their memory and learning test scores improved, said J. Glenn Morris of the University of Maryland Medical School. Within six months, all the subjects had returned to normal test ranges, he said, although some said they still did not feel they were completely back to normal.
Morris told a forum sponsored Tuesday by the National Sea Grant College Program that the “really striking” results indicate that pfiesteria does not have any apparent long-term effects on humans.
But he warned that it is still a serious ailment and one that needs more study.
“It’s not the sort of thing that you would want to willingly contract,” Morris said.
He noted that in medical exams of 13 people with long-term exposure to pfiesteria, most experienced an allergic-type reaction in the form of little red bumps, especially on their hands. But overall, the medical tests did not produce any noteworthy results.
Morris said neurological tests also showed an increase in metabolic activity in the frontal lobe of the brain, but researchers do not yet know its significance. It, too, returned to normal after six months, however.
The new research comes after a summer in which a predicted outbreak of the still-mysterious “cell from hell” never occurred.
JoAnn Burkholder, one of the scientists who discovered pfiesteria, said Tuesday that it is very difficult to predict what the organism is going to do.
Burkholder, a professor of botany at North Carolina State University, said all the right conditions for a toxic bloom can be present, then a storm will come in causing the pfiesteria to return to the bottom of the estuary.
Pfiesteria are commonly found in areas where fish and pollutants are plentiful and flushing is poor. They are difficult to detect because they can change colors and are able to quickly transform from one stage of their 24-form life cycle to the next.
Pfiesteria piscicida was first discovered in North Carolina waters in 1988. It turned up in Maryland in the fall of 1996, when watermen started noticing ulcers and erratic behavior in fish in the Pocomoke River and nearby Eastern Shore estuaries of the Chesapeake Bay.
The fishermen started experiencing health problems, such as respiratory irritation, memory loss, skin rashes and confusion around that time.
The subjects could have come in contact with the pfiesteria through direct skin contact or by breathing it off the water. But researchers were careful to note Tuesday that no humans have been affected by eating fish caught near pfiesteria-infested waters.
David P. Green, a food scientist and director of the North Carolina State University seafood laboratory, said that the edible tissues in shellfish and finfish have not proven to cause pfiesteria-related health problems.
“To date there has been no evidence for consumer concern,” he said. “There is no scientific evidence linking the presence of pfiesteria with seafood-borne illness. None has been reported in North Carolina, Virginia and Maryland in the past five years.”
Researchers also reported Tuesday that they are developing a device that could lower the cost of testing for pfiesteria from the current $1,500 per sample to about $15, and cut the process from two weeks to a few days.
Pfiesteria are currently identified by fish analysis and microscopically scanning the organism’s plate structure. Parke Rublee, an associate professor of biology at the University of North Carolina, is working on a field probe that can detect the presence of pfiesteria in its natural environment.
The field probes use DNA/RNA target sequences to distinguish pfiesteria cells from other organisms. Rublee said the field test will be combined with the current laboratory method to most accurately determine the presence of pfiesteria.
“The last thing we want are false positives,” he said.