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NIEHS Enters Investigation of Diseased Fish in
Pocomoke River

U.S. Senators from Maryland Barbara Mikulski and Paul Sarbanes formally asked NIH and the Centers for Disease Control and Prevention Aug. 11 to help investigate a mysterious disorder affecting fish in the Pocomoke River in southeastern Maryland. Since last October, thousands of catfish, perch and other seafood have become infected with red lesions and open sores; most of the infected catch later die as a result of the unknown disorder. In addition, several watermen and others exposed to waterways in the Chesapeake Bay region recently have become ill and/or have shown signs of developing lesions. Although a link has not been established between the fish illness and that suffered by humans, the possibility of a connection has not been ruled out.

Studies of the fish, water quality testing and other marine disease research have been ongoing in the months since the problem's initial discovery, however the possibility of a human health risk prompted the senators immediately to enlist NIH's expertise and resources to find the source of the disorder. About 5 miles of the river had been closed to the public in recent weeks because of the possible health threat; officials reopened the sections Aug. 13. Mikulski and Sarbanes toured the Pocomoke about 2 weeks ago to see firsthand the effects of the disease.

"We ask that you make toxin and human health effects experts available to Maryland and dispatch a team of top scientists to help the state with its investigations," the senators wrote in an Aug. 11 joint letter to NIEHS director Dr. Kenneth Olden. Although Maryland has assembled an investigative team, the letter continued, "additional resources, expertise and equipment are urgently needed to assist with performing medical evaluations, developing the necessary epidemiological information, increasing surveillance efforts, and responding to public health problems."

A number of marine biologists as far away as North Carolina and Florida have been consulted about what is causing the fish ailment, which closely resembles Pfiesteria piscicida, a type of toxic algae that was first noted in Chesapeake Bay estuaries about 4 years ago. The same algae has been blamed for killing close to a billion fish about half the recent mass fish kills in North Carolina.

According to a July 1996 issue of NIEHS's Environmental Health Perspectives journal, the pfiesteria alga is attracted by fish secretions and targets certain kinds of freshwater creatures. Known as an ambush-predator, the alga "puts fish into a narcotic stupor, strips off and eats their skin, then suffocates its victims by paralyzing them," the article said. Prone to thrive in nutrient-laden waterways, the organism has also been identified in coastal waters of Florida, Georgia and South Carolina. Some evidence suggests that such toxic algae blooms are on the increase worldwide.

NIEHS extramural researchers at the University of Miami Marine and Freshwater Biomedical Science Center, working in collaboration with the N.C. State University investigators who first described the N.C. fish deaths, have already identified at least two harmful agents from the extracts of the pfiesteria organism. Both intramural and extramural NIEHS scientists continue to work on the alga investigation. NIEHS plans to sponsor a workshop later this month on marine toxins to examine the possible expanded roles the institute might undertake to evaluate environmental health aspects of algal blooms and related toxins.

NIH and CDC join in this effort with two other federal agencies, the National Oceanic and Atmospheric Administration and the Environmental Protection Agency, which were asked by the Maryland senators in June to provide scientists, lab facilities and $500,000 in emergency funds for research and water testing.

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