Since the late 1980s, a new word Pfiesteria has entered our vocabulary. Pfiesteria, a microscopic marine organism, has been linked to fish kills and human health problems along the Mid-Atlantic coast and beyond. The organism has become the subject of national press coverage, as well as the cause of considerable confusion and speculation.

Thanks to the efforts of the scientific community, we are steadily learning more about Pfiesteria, its biology, and its impacts. Researchers also are advancing our ability to detect Pfiesteria in coastal waters.

Biology of Pfiesteria

Pfiesteria is a one-celled organism called a dinoflagellate. It exhibits characteristics of both plants and animals. One of Pfiesteria's most remarkable features is its multiple life stages. Most of these stages are benign. However, a few are toxic and harmful to fish and humans.

Laboratory experiments have demonstrated that Pfiesteria can become toxic in the presence of fish. In a matter of hours, the organism can change from a resting cyst stage, to an amoeba-like form, to a swimming stage -- the stage most threatening to fish. Affected fish, partially paralyzed from toxin, start gasping at the water's surface, or may be found dead or dying, sometimes with round, bleeding sores in their flesh.

These changing forms make Pfiesteria piscicida and its close relatives -- now often referred to as the "Pfiesteria complex" -- both intriguing and difficult to confirm. Scientists have developed molecular probes that detect the presence of Pfiesteria in coastal waters, and they are working on new probes that will aid coastal states in rapidly detecting and responding to toxic Pfiesteria incidents.

Human Risk

Pfiesteria has the unusual ability to produce toxins which can aerosolize, or become airborne. Medical researchers have found that people with high exposure to waters surrounding fish kills may experience short-term memory loss as well as the loss of concentration needed to perform daily tasks. Over time, the ability to concentrate and maintain memory is regained. Exposure to Pfiesteria also has been linked to skin rashes.

More critical symptoms -- including narcosis ("a drugged effect"), severe headaches, acute loss of short-term memory, and impaired liver and kidney function -- have been reported by researchers who worked with high concentrations of the organism in its toxic form in the laboratory.

Scientists are continuing to pursue intensive research to identify Pfiesteria's chemical toxins and to study Pfiesteria's impact on human health.

Pfiesteria and Seafood

There have been no confirmed reports of people getting sick from eating seafood that may have been exposed to Pfiesteria. While a number of fish and shellfish may be affected, most fish kills in which Pfiesteria has been implicated have involved menhaden, an oily fish which is not marketed as human food but rather as bait fish and fertilizer. Restaurant and retail seafood must meet state and federal safety guidelines.

Precautions