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There has been a recent media
onslaught centered on a microscopic, unicellular organism - technically
a dinoflagellate - named Pfiesteria piscicida. This organism, proven to
have caused a number of fish kills in the Chesapeake region and a complex
of physical disorders in researchers and technicians working on it, is
responsible for a multi-state task force, for a significant decrease in
seafood sales affecting much of the Mid-Atlantic, for a number of Pfiesteria
hotlines, for a tremendous amount of public concern, for several
television “specials” and for seemingly countless words giving particular,
and possibly self-serving, spins to what is at this point a relatively
meager amount of hard data.
| Much, if not most, of the
information on Pfiesteria is available through the World Wide Web. A simple
Alta Vista
[  ]
search for “Pfiesteria” yielded over 900 hits. This internet activity illustrates
some of the most positive as well as negative aspects of the Web. On one
hand, factual and up-to-the-minute research findings are available at the
“official” sites (visit those referenced here). On the other, some sites
are using the interest in Pfiesteria to contribute further to what has
already been termed “Pfiesteria hysteria." |
Pfiesteria-related illnesses
have been documented among researchers (particularly Dr. Joann Burkholder,
the North Carolina State University researcher who has done much of the
pioneering work on the organism, and her colleagues) coming in close, day-to-day
contact with the organism. Whether any illnesses can be attributed to people
coming in contact with the organism outside the laboratory has yet to be
determined [From the University of North Carolina website ].
While there has been a detectable decline in consumer confidence in locally produced seafood in the Mid-Atlantic, there has not been any indication that consuming fish or shellfish from “infected” waters is deleterious to human health. Quoting from a September 19 press release from the National Fisheries Institute, a trade association representing over 1000 companies involved in all aspects of the seafood industry, “Pfiesteria is not an infectious or contagious disease - it cannot be caught like a cold. There is no evidence that it can be passed along in the food chain, or passed from fish to human....No cases of seafood poisoning have been reported from eating fish exposed to Pfiesteria. Nor has there been evidence of tainted shellfish, oysters or crabs on the market.” (NFI contacts are Emily Holt or Pam Glass at 703-524-8881)
There has been a great deal of
speculation that nutrient enrichment of the waterways, possibly from agricultural
run-off, is causing the Pfiesteria blooms. This has not been proven either.
(from the American Farm Bureau website at www.fb.com/issues/analysis/pfiesteria.html]
As mentioned above, the governors
of Pennsylvania, Delaware, Maryland, Virginia, West Virginia and North
Carolina have formed a Task Force to provide a coordinated Pfiesteria research
program (Six states join Pfiesteria summit, UPI Science News - Yahoo News
- -
9/19/97). Several federal agencies, including the Geolgical Survey, the
National Marine Fisheries Service, the U.S. Department of Agriculture and
the Environmental Protection Agency have also been involved. A number of
universities and research institutions have initiated agressive Pfiesteria
research programs and several millions of dollars have been made available
to support this vital research effort.
Finally, there has been a well-coordinated
and effective outreach program coming from a number of institutions and
agencies providing authoritative and timely information on Pfiesteria (web
sites and telephone contacts are referenced on the next page). Collectively
they are invaluable in gaining an understanding of an extremely complex,
but by no means catastrophic, situation.
| Pfiesteria is a pretty gruesome organism,
but is it uniquely gruesome?
When particular aspects of Pfiesteria’s life cycle are presented in the popular press, or even in the technical literature, they can appear to be the stuff that horror movies are made of. For example: “Pfiesteria piscicida has a complex life cycle that includes at least 24 flagellated, amoeboid, and encysted stages or forms. Both flagellated and amoeboid forms are known to be toxic to fish....the cyst (dormant) stages...commonly occur among the bottom muds of North Carolina’s estuaries. Amoeboid stages can be found in the water column as well as among the bottom sediments; they feed on other organisms (bacteria, algae, small animals) or on bits of fish tissues by engulfing their prey. Flagellated stages...can also engulf similar prey, but more often they feed, instead, by attaching to prey cells using a cellular extension called a peduncle and suctioning the prey contents. Pfiesteria often makes its
living as a nontoxic predatory animal, becoming toxic when it detects enough
of an ephemeral substance that live fish excrete or secrete into the surrounding
water. When fish (e.g., a large school of oily fish such as Atlantic menhaden)
swim into an area and linger to feed, their excreta triggers encysted cells
to emerge and become toxic. Active amoeboid and flagellated cells which
are present also become toxic in the presence of the fish excreta. The
small cells swim toward the fish prey and, in turn, excrete potent toxins
into the water which make the fish lethargic so that they tend to remain
in the area. The toxins also injure the fish skin so that they lose their
ability to maintain their internal salt balance. As the skin is destroyed,
open bleeding sores and hemorrhaging often occurs. Once fish are incapacitated,
Pfiesteria feeds on the sloughed epidermal tissue, blood, and other substances
that leak from the sores. When the fish are dead, flagellated stages transform
to amoeboid stages and feed on the fish remains or, alternatively, if conditions
become unfavorable (e.g., sudden storm), Pfiesteria cells make protective
outer coverings and sink out of the water column as dormant cyst stages.
All of these changes can take place in a matter of hours.” (from the NCSU
Aquatic Botany laboratory Pfiesteria piscicida homepage But compare this to the following
description of the life cycle of the parasite Sacculina, a member of the
order of crustaceans called barnacles that are usually found growing on
rocks or boat bottoms delicately sifting small organisms out of the water
with their feathery appendages. (The words in parantheses were added for
clarity).
Compared to Sacculina (which, we emphasize, has absolutely no effect on the quality or the wholesomeness of crabs coming to market), Pfiesteria doesn’t seem quite so horrible or quite so unique. The world out there is filled with little beasties that, were we more familiar with them, would provide us with enough inspiration for a lifetime of bad dreams. |
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