Pfiesteria Infections

Introduction
What Is Pfiesteria?
Biology of Pfiesteria
Human Risk
Pfiesteria and Seafood
Treatment

Pfiesteria piscicida, a tiny marine organism identified in the last decade in estuaries in North Carolina and Delaware and in the Chesapeake Bay and its tributaries, has been blamed for killing fish and causing health problems in humans.

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.

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.

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.

• Leave an area where fish are floating at the water's surface -- a fish kill may be in progress.
• After swimming or wading in coastal waters, rinse with tap water.
• If you fish recreationally, do not keep fish with sores or lesions.
• Avoid touching sores or lesions of dead or dying fish. If you must handle fish with sores, use gloves.
• As a general precaution, consumers should completely cook finfish and shellfish. Never eat fish that exhibit evidence of sores or disease. Do not eat fish that seem diseased or dying when caught.
• If you experience illness you think is related to exposure to Pfiesteria, please see your physician.