Early results from a new study suggest that people who get sick from Pfiesteria once may be much more vulnerable to getting it again.
A handful of Marylanders who probably were exposed twice to the toxic microorganism -- once in 1997, at levels high enough to kill fish, and again in 1998 at much lower levels -- appeared to suffer "mild to moderate" short-term memory problems last summer, after their second round of exposure, said University of Maryland neurologist Dr. Lynn Grattan.
Grattan's findings -- which she described as the preliminary results of a study of about a dozen patients -- mark the first time a researcher has shown that some Marylanders got sick from Pfiesteria in 1998, a year when there were no outbreaks serious enough to cause fish kills.
The research "raises the possibility that upon repeated low-level exposures the symptoms may come and go," Grattan said in an interview yesterday.
The findings pose problems for Maryland health and natural resource officials as they try to decide when to close rivers and streams to protect the public from Pfiesteria. Last summer, the state used guidelines that relied on large numbers of lesioned, dying or distressed fish as a sign of dangerous Pfiesteria levels.
Pfiesteria did appear at low levels in the Wicomico and Chicamacomico rivers last year -- but fish health problems never crossed the state's thresholds, so those rivers were presumed to be safe for people.
Grattan said all of the people in her study spent time on at least one of those rivers last summer, and at least two of them showed "mild to moderate disturbances in attention, memory and learning ability" in tests taken shortly after their time on the water. Results are less clear in a few other cases, she said, but on further analysis the number of people affected may grow.
State officials hope that by next year, new scientific tools will make it easier to spot the presence of Pfiesteria even at low levels, alleviating the need to rely on sick or dying fish as a danger signal, said John Surrick, a spokesman for the Maryland Department of Natural Resources.
Surrick said his agency and the Maryland Department of Health and Mental Hygiene have begun reviewing the criteria they use for closing rivers to protect people from Pfiesteria. "We will be taking a look at all the new information we've learned from last year and look at the protocols and determine if any changes need to be made," Surrick said. The guideline revisions should be finished by May, he said -- before the risk of toxic Pfiesteria outbreaks, which rises with water temperatures during the summer.
Because so little is known about Pfiesteria, Maryland officials had very little to go on other than fish health problems as a warning sign of possible human health effects, Grattan said.
"The lack of closures or aggressive warnings to stay away might not be out of naivete, but just because of a lack of data," she said. "Twenty years from now, looking back and seeing what happened, it will probably all make sense, but right now we have a lot to learn."
Grattan is a member of the Maryland Medical Team, the group of researchers who first showed in 1997 that Pfiesteria can cause human health effects. As a result of the team's work, the short-term memory problems associated with Pfiesteria have a name -- "estuarine associated syndrome" -- and are recognized by scientists elsewhere.
Grattan and other team members are working on a five-year study of Eastern Shore watermen. Her current findings, however, are the earliest results from a smaller, independent study she is conducting.
Dr. Glenn Morris, head of the Maryland Medical Team, and Dr. David Oldach, head of the long-term study, could not be reached for comment on the findings from Grattan's study yesterday. At a scientific symposium on Pfiesteria last month, Oldach said preliminary results from the long-term study did not suggest any illnesses as serious as those seen in 1997.
Grattan agreed, stressing that none of her patients were new cases of people exposed to Pfiesteria only once. All suspected they were exposed to Pfiesteria in 1997, when it caused several fish kills in the Pocomoke and other Lower Eastern Shore rivers, but none came forward at the time "because they weren't sure if they believed in it," Grattan said.
"And then in 1998, around the time we had these low levels" of toxic Pfiesteria on the Wicomico and Chicamacomico, "these people felt their symptoms had come back," Grattan said. The patients called Grattan directly or reached her through state or county health departments. They were given standard tests of memory and intelligence in July, August and September, and again six months later.
For some of the patients, "It does not look like they were doing as well back then as they are now," Grattan said. The summer's test showed results "maybe 25 to 30 percentile points below what would be expected," she said.
In 1997, Grattan conducted brain scans called "positive emission tomography" on some people exposed to Pfiesteria in 1997. The results showed a pattern of abnormal activity in certain parts of the brain. But Grattan said none of the people who first reported symptoms in 1998 have had the PET scans, because they involve radiation and aren't recommended for milder abnormalities.
Grattan's findings came as no surprise to North Carolinians who have been repeatedly exposed to Pfiesteria.
"That's very consistent with what I see both in myself and others," said Neuse Riverkeeper Rick Dove, a conservationist whose full-time job is patrolling the North Carolina river.
"I can be on the water and I can be in an area where I can't see any dead fish, but I'll start experiencing symptoms. My lips will burn, my eyes will burn, my skin will burn," he said. "Some fishermen come in off the water and can't find their way home. That hasn't happened to me. My wife is better able to see those memory changes than I am. I don't feel it."
"When you have toxin around at these much lower levels, it's much harder to be sure" about Pfiesteria's effects, Dove said. But with each new piece of information, "it begins to make a lot more sense."
Pub Date: 3/26/99