department of things we should have known were evil
An excerpt from Taras Grescoe's book Bottomfeeder follows. Short version: you should not be eating farmed shrimp, especially imported farmed shrimp, unless you are a big fan of diesel oil, carcinogens, and drug-resistant salmonella. This is pretty much all inexpensive shrimp, including the stuff at your local chain restaurant or supermarket.
- According to Tamil Nadu's fisheries department, a dry pond should be prepared by spreading urea and superphosphate to encourage plankton growth. Once the pond has been filled with brackish water, generally pumped from a nearby creek, it is typically covered with diesel oil to kill off any insect larvae. The water is then treated with a piscicide-- a substance that poisons any competing aquatic life-- such as chlorine or rotenone; the latter has been strongly linked to Parkinson's disease in humans.
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As the shrimp grow, the water is treated with pesticides and more piscicides, but by far the gravest concern is the use of antibiotics to ward off disease. Acutely toxic to other marine organisms, they can cause contact dermatitis in the shrimp farm employees who administer them. When the plug is pulled on the ponds at the end of the growing season, hundreds of pounds of shrimp remain marinating in the toxic mud at the bottom, and pickers have to be hired to scoop up the stranded shrimp.
Farmers . . . naturally deny they use antibiotics, knowing full well they are banned in important export markets. When shrimp are tested, however-- and the FDA checks less than two percent of seafood imported into the United States-- prohibited chemicals are still found. In Louisiana, which does rigorous testing of its own, the antibiotic chloramphenicol, known to cause leukemia and aplastic anemia, was found in nine percent of all samples.
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Food safety experts have discovered that some people who believe they have shellfish allergies are actually exhibiting reactions, like itching and swelling, to antibiotic residues in farmed species.
A good indicator of antibiotic use, even if the chemicals have already been eliminated from the tissue of the shrimp, is the presence of antibiotic-resistant pathogens, such as typhoid and salmonella. Researchers at Mississippi State bought thirteen brands of ready-to-eat shrimp-- some packaged with cocktail sauce-- and found 162 separate species of bacteria, showing resistance to ten different antibiotics, including chloramphenicol. Their conclusion: consumers, particularly those with depressed immune systems, are probably better off cooking ready-to-eat shrimp.