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Pfiesteria: How the Meat Industry Destroys Waterways

A marine scientist in North Carolina developed sores on his skin, tingling in his hands and feet, and difficulty walking. He had been working with samples of pfiesteria, a microorganism that has caused massive fish kills in rivers up and down the eastern seaboard. 1 He was not alone. Thirteen other researchers reported adverse reactions as did many fishers. In 1995, pfiesteria killed 14 million fish in the Albermarle-Pamlico estuarine system of North Carolina, which makes up about half of the breeding area for fish species along the mid-east coast. It has killed over one billion fish in North Carolina. Pfiesteria piscicida (pronounced fee-STEER-ee-uh pis-kuh-SEED-uh) was discovered by JoAnn Burkholder, Ph.D., of North Carolina State University. Fish kills in the waterways surrounding the Chesapeake Bay and as far north as Delaware Inland Bay have been linked with the toxic microbe. As for the marine scientist from North Carolina, the Journal of Toxicology and Environmental Health reports that most of his symptoms have been resolved after two years time except for some “mild sensory symptoms” brought about by light exercise. He is still being evaluated for long term effects.

What Is Pfiesteria?

Pfiesteria, a one-celled microorganism referred to as a dinoflagellate, is neither a plant nor animal. Some scientists believe pfiesteria has existed in shallow estuaries for thousands of years and only becomes toxic under certain conditions, such as an increase in nutrients in the water. Menhaden, the fish species affected in 90 percent of pfiesteria-related kills, have oily secretions that are thought to stimulate the toxic microbe.2

Pfiesteria detects fish by either their skin secretions or excrement, becomes toxic, and then stuns the fish. It then feeds on the fish’s blood and skin, leaving open and bloody sores the size of a dime. Pfiesteria can also kill fish without causing visible lesions. It is believed that some of the fish kills in the tributaries of the Chesapeake are not caused by pfiesteria, but by related toxic organisms which, nevertheless, behave like pfiesteria.

In October 1996, fishers found lesions on fish in the Pocomoke River, a tributary of the Chesapeake Bay. However, initial tests for the presence of pfiesteria came up negative. In April 1997, more fish lesions were reported, and some fishers complained of feeling ill. Since then, fish kills have occurred in several eastern states.3

Pfiesteria and Human Health

Exposure to pfiesteria can occur through direct contact with intact skin or open wounds, inhalation of airborne toxins, and/or by ingestion.4 Reported symptoms include sleepiness, open sores, reddening of the eyes, severe headaches, blurred vision, nausea, vomiting, difficulty breathing, kidney and liver dysfunction, memory loss, and severe cognitive impairment.5 Most symptoms are thought to be reversible over time.

Most scientists believe that pfiesteria’s recent aggressiveness is caused by excessive nitrogen and phosphorous found in animal waste which is applied to croplands as a fertilizer in watershed areas. In North Carolina, a state notorious for its hog production, watersheds with large numbers of livestock populations discharge five to ten times more nutrients than those without such populations.6 Runoff from housing developments, golf courses, and failing septic systems also add pollutants to the water.

Many scientists and environmentalists have pointed to chicken waste from farms along the eastern shore of Maryland as a primary cause of recent outbreaks of pfiesteria. According to the Delmarva Poultry Industry, Inc., 623 million chickens are produced and slaughtered in the Delmarva peninsula area each year.7 In areas bordering the Chesapeake Bay along the eastern shore, 62 million chickens produce nearly 3.3 billion pounds of raw waste. This waste contains approximately 13 million pounds of phosphorous and 48 million pounds of nitrogen.8 The watershed area of the Pocomoke River houses over 100 million chickens and 60,000 hogs, producing close to 250 million pounds of manure each year, along with bedding litter and the remains of chickens killed in production.4

Cleaning up Pfiesteria

Even prior to pfiesteria outbreaks, environmentalists warned of the dangers of large-scale chicken and hog operations. With the emergence of the new threat, Maryland Senator Brian E. Frosh called for a moratorium on the expansion of chicken farms. Unfortunately, the commission charged with investigating the toxic pfiesteria outbreaks voted six to two to reject the ban. Other proposals calling for voluntary limits on waste and government aid are being considered.

Individuals can help by reducing or eliminating their consumption of chicken and pork. By doing so, even for a short period of time, production would be slowed.

If chicken consumption were decreased to the extent that chicken production in Maryland dropped 25 percent, that would mean 15.5 million fewer chickens raised and slaughtered each year. Annual production of raw wastes would decrease by 816 million pounds, cutting the amount of nitrogen and phosphorus that could potentially find its way into the watershed areas by 12 million pounds and 3.4 million pounds, respectively. Replacing chicken and pork with spaghetti, bean and vegetable dishes, and other non-animal foods would also mean less risk for foodborne illness, such as salmonella poisoning, and less fat and cholesterol to contribute to heart attacks and some forms of cancer. The rivers might not be the only things that would regain their vitality.


1. Burkholder JM, Glasgow HB. Insidious effects of toxic estuarine dinoflagellate on fish survival and human health. J Toxicol Environ Health. 1995;46:501-522.
2. Burkholder JM. Pfiesteria piscicida and other toxic pfiesteria-like dinoflagellates. North Carolina State University, 1997.
3. Testimony by Parris Glendening before the Human Resources Subcommittee, Committee on Government Reform and Oversight, 1997.
4. Chesapeake Bay Foundation. Facts about pfiesteria piscicida in the Chesapeake Bay, 1997.
5. NCSU Aquatic Botany Laboratory, Raleigh, North Carolina, 1997.
6. Corell DL, Jordan TE, Weller DE. Livestock and pasture land effects on the water quality of Chesapeake Bay watershed streams. In: Steele K, ed. Animal Waste and Land-Water Interface. Lewis Publishers, 1995, pp. 107-17.
7. Delmarva Poultry Industry, Inc. Look what the poultry industry is doing for Delmarva: 1995 facts about Delmarva’s boiler industry.
8. Shields T, Warwick J. Md. counties awash in pollution-causing nutrients. The Washington Post. Oct. 3, 1997.


Winter 1998

Winter 1998
Volume VII
Number 1

Good Medicine

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