By David Brown
Washington Post Staff Writer
Friday, August 14, 1998; Page B01
People heavily exposed to the fish-killing microorganism
Pfiesteria piscicida can develop severe difficulties in learning
and concentrating, according to new research.
The problems go away in a few months, with cognitive
ability returning to normal. Other signs of toxin exposure, such
as skin sores, are less common than the mental changes.
The conclusions were reached by a team of Maryland
researchers and are reported in tomorrow's edition of the Lancet.
The study, the first of people with environmental exposure to
pfiesteria to be published in a medical journal, supports earlier
concerns that the unusual single-cell organism can pose health
hazards to people.
The researchers examined and tested a small
group of Eastern Shore residents, including eight fishermen, who
were exposed last August during a fish kill on the Pocomoke River.
"I can tell you that in talking to them
[as a physician], there clearly were difficulties," said
J. Glenn Morris Jr., an infectious diseases specialist at the
University of Maryland School of Medicine in Baltimore. "What
we were able to show is that objective data in neurocognitive
tests fits very well with the problems they were reporting."
Among the most heavily exposed, problems included
not remembering where they were driving or for what purpose; forgetting
they had done an errand, such as mailing a package; and, in the
case of the watermen, finding themselves on board their boats
without supplies they normally brought.
Pfiesteria, which was discovered in 1995, killed
more than a billion fish in coastal North Carolina over the past
decade before striking Chesapeake Bay tributaries for the first
time last summer. Maryland state officials briefly closed parts
of the Pocomoke and adjacent waterways last August in response
to pfiesteria-related fish kills there.
Last month, as many as a half-million fish died
during one week-long attack in North Carolina's Neuse River. Although
menhaden with pfiesteria-like sores were found last week on the
Eastern Shore's Wicomico River and Shiles Creek, no serious outbreaks
have occurred so far this year in Maryland or Virginia.
Morris and his colleagues at Johns Hopkins University
and at the public health departments of Baltimore and Somerset
County gave a battery of neurological and psychological tests
to 19 men and women who reported health problems after contact
with the Pocomoke during the fish kill. The exposures ranged from
days on end for the watermen to brief visits by recreational boaters
and biologists taking water samples. The exposed group was compared
with an "occupationally matched" control group.
Both groups had slightly above average IQs,
and no one in either group showed evidence of psychiatric illness.
(One person in the original exposed group was removed from the
study because of what appeared to be exaggerated symptoms.) On
a dozen neuropsychological tests, the two groups scored virtually
the same. On three, however, there were significant differences,
with the heavily exposed people performing poorly compared with
their counterparts in the control group.
In one of those tests, a person is given a list
of 15 unrelated words and is asked to recall them later. This
tests learning. In another, a person must concentrate on a confusing
mixture of colors and words. This tests the ability to filter
out extraneous information. In the third, fine-motor skills are
tested by seeing how quickly a person can put shaped pegs in a
pegboard.
In some cases, the scores were remarkably low.
Most of the eight heavily exposed watermen, for example, scored
worse in the word-recall test than 95 percent of the general population.
"They really had a very isolated deficiency
in their learning ability," Morris said.
The researchers tested both groups again three
months later. All but two of the people exposed to pfiesteria-laden
water had test scores in the normal range. At six months, those
two people had normal scores, also.
The exposed people also reported other symptoms.
Some had headaches, others breathing problems and intestinal complaints.
Four had skin sores of varying types. None of the physical findings
was as consistent as the neuropsychological deficits.
Pfiesteria's toxin has not been purified, and
the exact mechanism of its effects on the nervous system is not
known.
Five people who had contact with estuarine waters
in recent months reported health problems and called a hot line
run by the Maryland Department of Health and Mental Hygiene are
now being evaluated for possible pfiesteria exposure.
Staff writer Joby Warrick contributed to this report.
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