New research disputes claim that Pfiesteria has poison dangerous to humans
Monday, August 5th 2002, 12:00 am
By: News On 6
WASHINGTON (AP) _ Two teams of researchers say they cannot confirm the claims of a decade-old study that indicated that pfiesteria, a parasitic algae that plagues Eastern coastal waters, can make a toxin that kills fish and makes people sick.
Fear of pfiesteria in recent years has caused state officials to close some coastal waters after fish kills and to warn anglers to avoid fish with raw sores.
The fear was boosted by a British medical journal finding that 19 people suffered fatigue, headaches, diarrhea and losses in mental agility after they were exposed to the waters of the Pocomoke River in Maryland after a massive fish kill. The study said the illnesses may have come from a toxin given off by pfiesteria in the dead fish.
But the new studies say that pfiesteria is not to blame, suggesting indirectly that the work of North Carolina State researcher JoAnn Burkholder is flawed. Burkholder first reported in 1990 that pfiesteria was dangerous to both fish and humans. Her research has been widely publicized and was featured prominently in a book called ``And the Waters Turned to Blood.''
Robert E. Gawley, an organic chemist at the University of Miami, said that much of what Burkholder claims cannot be confirmed by other labs.
``We set out to isolate and identify the toxin,'' said Gawley. ``We didn't find it.'' He said an additional study shows that pfiesteria does not even have the gene that other algae use to make toxins.
Gawley is co-author of a study appearing this week in the Proceedings of the National Academy of Sciences. Another group, at the Virginia Institute of Marine Sciences, say in a study appearing Thursday in Nature, that their studies suggest that pfiesteria kills only by directly gnawing at fish and not by some poisonous chemical.
If pfiesteria doesn't make a toxin, then is it dangerous to humans, as Burkholder and others have claimed?
``We're really skeptical of those reports,'' said Jeffery Shields of VIMS, a co-author of the Nature study. He said he and his colleague, Wolfgane Vogelbein, checked some sores on dead fish and found they were caused by a mold that is harmless to humans.
Burkholder, contacted by phone, dismissed the new studies, saying that other labs have confirmed her work. She said Gawley and Shields used the wrong techniques and the wrong strain of pfiesteria, which she said is a bizarre, poorly understood form of plant life that goes through cycles of being toxic and nontoxic.
Pfiesteria must be carefully cultured to produce its toxin, said Burkholder. She said the labs of Gawley and Shields lack the skills and training needed to bring out the deadly nature of the microorganism, she said.
Gawley's study, financed by the Environmental Protection Agency, cultured pfiesteria in tanks and exposed it to sheepshead minnows.
``We could kill fish with pfiesteria, but when we looked for the toxin it wasn't there,'' he said.
The researchers collected organic extracts from the dead fish and the tank and put them through a complex chemical analysis searching for poison. They found none.
They chopped up pfiesteria, thinking that perhaps the poison is released, as with some algae, when the organism dies. There was no toxin. When the residue was put into a tank of healthy fish, the fish thrived.
Finally, Gawley said they went looking for a gene that in other algae makes a fish-killing toxin. Pfiesteria does not have that gene, he said.
In the Shields study, the researches constructed a system of membranes that separated fish from pfiesteria. The membranes permitted the passage of toxins, but blocked the pfiesteria itself. There was no toxin and the fish lived.
Only when pfiesteria was placed directly on the fish did it become deadly, said Shields. Highly magnified views showed that the organism actually chewed up the fish, virtually skinning it alive. The fish died of shock and infection.
``There was no toxin,'' said Shields.
Both Gawley and Shields said Burkholder's work would have more credibility if she would freely share with other labs her pfiesteria cultures, a common practice in science.
Burkholder said that it would be useless to distribute her specimens because most other labs lack the specialized knowledge needed to culture pfiesteria properly and to cause it to make the toxin that she said she has found.
The toxin has been found, said Burkholder, in the labs she has selected to receive her pfiesteria cultures.