| Pfiesteria piscicida | |
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Scientific classification | |
| Domain: | Eukaryota |
| Clade: | Diaphoretickes |
| Clade: | Sar |
| Clade: | Alveolata |
| Phylum: | Myzozoa |
| Superclass: | Dinoflagellata |
| Class: | Dinophyceae |
| Order: | Thoracosphaerales |
| Family: | Pfiesteriaceae |
| Genus: | Pfiesteria |
| Species: | P. piscicida |
| Binomial name | |
| Pfiesteria piscicida | |
Pfiesteria piscicida is adinoflagellate species of the genusPfiesteria that some researchers claim was responsible for manyharmful algal blooms in the 1980s and 1990s on the coast ofNorth Carolina andMaryland. North Carolinian media in the 1990s referred to the organism asthe cell from hell. It is known to populateestuaries.[1]Piscicida means "fish-killer".
Early research suggested a very complexlife cycle ofPfiesteria piscicida with up to 24 different stages, spanning fromcyst to severalamoeboid forms with toxiczoospores. Transformations from one stage to another depend on environmental conditions such as the availability of food.[2] However these results have become controversial as additional research has found only a simplehaplontic life cycle with notoxic amoeboid stages[3] and amoebae present on attacked fish may represent an unrelated species ofprotist.[4][5]
Pfiesteria presumably kills fish via releasing atoxin into the water to paralyze its prey. This hypothesis has been questioned as no toxin could be isolated and no toxicity was observed in some experiments. However, toxicity appears to depend on the strains and assays used.[6]Polymerase chain reaction-analyses suggested that the organism lacks theDNA forpolyketide synthesis, the type of toxins associated with most toxic dinoflagellates.[7] Researchers from theNOAA National Centers for Coastal Ocean Science, theNational Institute of Standards and Technology, theMedical University of South Carolina, and the College of Charleston (S.C.) have formally isolated and characterized the toxin in the estuarine dinoflagelletePfiesteria piscicida as a metal complex and free radical toxin and also have identified how the organism transforms from a non-toxic to toxic state.[8][9][10][11]
Very little research on the human health effects ofPfiesteria toxins has been conducted. At a multi-state workshop at theCenters for Disease Control and Prevention (CDC) inAtlanta,U.S., at the end of September 1997, attendees agreed on clinical symptoms that characterize a new illness associated withPfiesteria exposure. These clinical features include:
With these criteria and environmental qualifiers (e.g., 22% of a 50-fish sample, all of the same species, have lesions caused by a toxin), it is likely thatPfiesteria-related surveillance data can better track potential illnesses.
Pfiesteria toxins have been blamed for illness in those who have come in close contact with waters where this organism is abundant. Since June 1997, theMaryland Department of Health and Hygiene has been collecting data from Maryland physicians through a statewide surveillance system on illnesses suspected of being caused byPfiesteria toxin. As of late October 1997, illness was reported by 146 persons who had been exposed to diseased fish or to waters that were the site of suspectedPfiesteria activity. Many of these persons are watermen and commercial fishermen.
The strongest evidence ofPfiesteria-associated human illness so far comes from case studies of two research scientists who were both overcome in theirNorth Carolina laboratory in 1993. They still complain of adverse effects on their cognitive abilities, particularly after exercising.Duke University Medical Center researchers conducted experiments on rats, which showed that the toxin appeared to slow learning but did not affect memory.[12]
Treatment withColestyramine shortly after exposure has been shown to alleviate symptoms.[13]
This article incorporates text from this source, which is in thepublic domain: a report by theCongressional Research Service (CRS), part of theLibrary of Congress
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