Flap over fish lesions Sores may be formed by fungus, not just Pfiesteria, says expert

Md. official disagrees

Presence of sores used as warning sign that toxin is in water

September 23, 1998|By Heather Dewar | Heather Dewar,SUN STAFF

In a new scientific controversy that points out how little is known about Pfiesteria piscicida, a Virginia fish expert says Maryland officials may be placing too much faith in one of the key warning signs used to protect the public against toxic outbreaks of the microorganism.

The bloody lesions that sometimes appear on menhaden during a Pfiesteria outbreak are not caused by Pfiesteria alone, but by another marine microorganism, said Wolfgang Vogelbein, a fish pathologist at the Virginia Institute of Marine Sciences. The aggressive fungus can take a long time to develop into a bloody sore -- and by the time affected fish are caught, they might be miles and weeks away from the place where they first picked up the parasite, he said.

The finding is important because Maryland state agencies use the presence of fish with lesions as one of three warning signs of Pfiesteria piscicida, which can cause memory loss and other health problems for humans. If enough menhaden with bloody sores turn up in a particular river or creek, guidelines call for the state health department to assume that a Pfiesteria outbreak is under way and keep people away from the waterway. If there are no signs of a fish kill, fish in distress or fish with lesions, the waterway is assumed to be safe.

That might be a mistake, Vogelbein said at a Washington news briefing on Pfiesteria research yesterday.

"Menhaden ulcers may not be an indicator of ongoing Pfiesteria activity," he said. "Their use to set public health action levels may not be valid on their own. The problem is that these lesions are old."

But top Pfiesteria expert JoAnn Burkholder said she is convinced that Vogelbein is wrong.

"During a Pfiesteria outbreak I have seen fish develop these lesions in a matter of minutes," Burkholder said in an interview after the meeting. "There's a whole array of things that can cause these lesions, but if Pfiesteria is around, you'd better get out of the way."

On-the-spot detection

Maryland's officials said they know the fish-with-lesions guideline not a fail-safe method for spotting toxic Pfiesteria.

"It's less than ideal, but it's the best that we've got," said David Goshorn, who supervises Pfiesteria monitoring for Maryland's Department of Natural Resources. "One of the great frustrations we all have is that with the technology that's out there now, we're still going out there and looking for lesioned fish, and then sending them off to a lab and waiting."

Dr. Glenn Morris, head of the Maryland medical team that first confirmed the microorganism's harmful effects, defended the use of fish with lesions as a signal of whether state waterways are safe from Pfiesteria.

"What you're seeing here is a learning process," Morris said. "Hopefully, come next summer, we are not going to be using the crude indicator of fish lesions."

A technique for on-the-spot detection of Pfiesteria's toxins is at least a year off, researchers said yesterday.

Progress has been made on more general tests for Pfiesteria, said North Carolina researcher Park Rublee. Three techniques were tested for the first time this summer, and they showed that the dinoflagellate was present in two Maryland rivers this year, he said.

But Pfiesteria has at least 24 different stages in its life cycle, most of them harmless, and the new tests cannot distinguish between the organism's toxic stages and the benign ones, Rublee said. Nor can it tell how much Pfiesteria is in the water. Researchers think it takes at least 100 Pfiesteria cells in every liter of water to make fish sick, and about 250 cells per liter to kill them.

Symptoms suffered this year

No one knows how much Pfiesteria it takes to make people sick, although Morris said the symptoms seem to get worse with prolonged exposure or during active fish kills.

Even though there have been no known Pfiesteria outbreaks in Chesapeake waters this year, the medical team has gotten reports of some patients who say they got sick after being exposed to local waters, and has tested some people for potential Pfiesteria exposure, Morris said. He refused to provide any details or to say whether the doctors have ruled out Pfiesteria as the cause of the patients' complaints.

"We have evaluated some individuals this year and I'd like to leave it at that for right now," Morris said. "We are not finished with the evaluation."

Pfiesteria has killed about half a million fish in North Carolina's Neuse River this year, Burkholder said. There have been no known Pfiesteria fish kills in Maryland this year, but state monitors found large numbers of menhaden with fresh lesions in Shiles Creek, near Whitehaven in the Wicomico River, in August, and in the Chicamacomico River this month.

Water samples from both of those incidents tested positive for Pfiesteria piscicida, said Rublee and Goshorn, but Burkholder said her lab has been unable to confirm toxic levels of Pfiesteria at either site so far.

Two of the new tests use DNA analysis to match up known segments of Pfiesteria's genetic code with the genetic signatures of unidentified cells. Those tests take from two to four days -- much faster than the three weeks to two months of current methods.

The third test uses a fluorescent biochemical marker that attaches itself only to Pfiesteria piscicida cells. Under a special microscope, the fluorescent Pfiesteria cells show up bright green against a dark background, sharply contrasted against the dull orange color of other microorganisms. That test takes about 24 hours, and researchers hope to cut that time to a matter of hours, Rublee said.

Pub Date: 9/23/98

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