What You Should Know About Pfiesteria

During the spring and summer of 1997, there have been numerous reports from the Delaware Bay, Atlantic Ocean and Chesapeake Bay of diseased finfish. One type of fish skin virus, called Lymphocystis, has been identified in Delaware. It causes reddened, bumpy skin and sometimes a milky coating. It is not harmful to humans and many fish recover from the problem. But it can weaken fish leading to other infections.

A second possible problem is called Pfiesteria, a toxic marine microorganism (sometimes confused with lymphocystis) which can cause red sores or lesions on any fish species and can lead to sudden, large fish kills.

The organism has been active in North Carolina for several years and may be a source of problems in other Mid-Atlantic states. Throughout the region, the news media has paid much attention to fish diseases, making Pfiesteria (pronounced feast-eer-ee-ah) an almost household name. We do know in Delaware that Pfiesteria has been identified in our Inland Bays and that it may have been responsible for a major fish kill in Indian River in June, 1987. And we know that is persists in the environment in a dormant state and can come alive again at any time, though it rarely does. Here's what else we know about Pfiesteria:


What is Pfiesteria?

Like many other organisms that inhabit our estuaries, Pfiesteria can be cause for concern. But, it is not cause for alarm or panic. It is a dinoflagellate—a microscopic organism that sometimes behaves like a plant and sometimes like an animal. It is a complicated organism, with at least two dozen life stages. In several stages, it produces neurotoxins that attacks fish. This organism has been found as far north as Indian River in Delaware and as far south as the Gulf of Mexico.

Pfiesteria appears to thrive in nutrient-rich waters. That’s why it could be a problem in Delaware's Inland Bays. In those areas, there are too many nutrients going into the bays from a variety of sources -- including runoff from developed areas, lawns, golf courses, farms and failing septic systems and discharges from wastewater treatment plants. The state is working with all citizens to try to clean up the Inland Bays, but those problems were not created overnight, nor will they disappear quickly.


When is Pfiesteria a Problem?

In North Carolina, Pfiesteria has only been a problem in the summer and fall and only in some locations. It is not a problem in the state’s inland fresh waters there and is not expected to be a freshwater problem here.


How do I know Pfiesteria if I see it?

One good indicator is open bleeding sores on coastal fishes. If 20 percent or more of the fish in a given area have sores, then that’s a good indication that Pfiesteria is active.


How does Pfiesteria affect seafood?

There is ongoing research on whether Pfiesteria affects the quality of seafood. Until that research is completed, you shouldn’t eat seafood with bleeding sores or peeled skin. You also shouldn’t harvest fish from an area where fish are sick or dying. Seafood from restaurants and retailers is carefully inspected before sale and is considered safe!


Does Pfiesteria make people sick?

There are no substantiated cases of humans who have been made ill by Pfiesteria, except for researchers who were breathing the toxins in a closed environment without proper protective equipment. The jury is still out on whether Pfiesteria can make people in “real world” situations ill. There is medical research underway to answer that question. Delaware’s coastal waters are safe for folks to visit and recreate in, if you take proper precautions. You should avoid swimming or recreating in waters where fish have sores or are dead, or dying.


Signs of Pfiesteria in Tidal Waters

1) Dead or dying fishes: 2) Dead or dying invertebrates: 3) Abnormal fish behavior: 4) If you answered yes to any of the above questions: If the answer is "yes" to Questions 1, 2, or 3, call the Delaware Department of Natural Resources Fish Kill Coordinator immediately! On weekdays, between 8 a.m. and 4:30 p.m., call (302) 739-3411. On weekends or after hours, call the DNREC Communications at (302) 739-4580 and stress the urgency of the problem.

As a precaution, until the cause of the fish kill can be determined, it is recommended that you avoid direct body contact with the water in the fish kill area; including swimming, water skiing, personal watercraft operation, fishing, clamming, crabbing or other recreational water activites. If you fall into the water, change any wet clothing and wash with soap and clean water. Keep pets from affected areas. Avoid touching any sores or lesions on the dead or dying fish and do not eat dead or dying fish or fish with sores. If you experience any illness that you think could be related to the fish kill, contact your physician promptly.

For more information:

For environmental information, call the Delaware Department of Natural Resources and Environmental Control Office of Information and Education at (302) 739-4506. For public health information, call the Delaware Division of Public Health at (302) 739-5617.

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The information in this brochure was developed by the Delaware Department of Health and Social Services and the Delaware Department of Natural Resources and Environmental Control.