August 28, 2012
At this summer’s annual Smithsonian Institute dinner, “Sustainable Seafood: Ensuring a Healthy Supply,” the question echoed by many guests was about the safety of imported shrimp. This year, I was an invited guest expert at the dinner, and I was joined at a table with Ed Rhodes, Vice President of Sustainability and Aquaculture Development at Phillips Foods, Inc. Ed and I fielded several questions from guests about sustainable seafood, but the emerging common concern was about imported shrimp.
Roughly 90 percent (or 1.3 billion pounds) of shrimp is imported from countries like Thailand, Ecuador, Indonesia, China, Mexico and Vietnam—a $6 billion dollar a year business. Generally, imported seafood is riskier than domestic seafood, likely because of difficulties in maintaining controlled temperature conditions during transit and less oversight and inspection by U.S. regulators and companies during production and processing. A survey by the U.S. Food and Drug Administration found that 7.2 percent of 11,312 imported seafood samples and 1.3 percent of 768 domestic seafood samples between 1990 and 1998 carried Salmonella (Heinitz et al., 2000).
As with any raw meat, seafood can contain spoilage and disease causing bacteria that could be risky for consumers. In one recent study, 1 in 3 packages of shrimp sold in Baton Rouge, Louisiana, grocery stores contained dangerous bacteria (Wang et al., 2011). These levels were somewhat higher in shrimp than in tilapia (1 in 4 packages) or salmon (1 in 5 packages). Cooking seafood thoroughly and practicing good hygiene in the kitchen, by cleaning up after yourself and not cross-contaminating meats with foods eaten raw, is always good advice.
Foodborne bacteria are not all the same. It turns out that different types of bacteria are present on farmed versus wild caught shrimp. A study by Clemson University researchers (Boinapally and Jiang et al., 2007) found a greater number of antibiotic-resistant bacteria in farm-raised shrimp (from Ecuador, Thailand, Vietnam, India, China and Honduras) than in wild-caught shrimp (from South Carolina), presumably due to antibiotics use on farms. Some of the bacteria found in farm-raised shrimp were resistant to multiple drugs.
The use of antibiotics in shrimp farming creates conditions where antibiotic resistant bacteria can proliferate on the farm, and these bacteria remain on the product and can also spread through the environment. In my view, is a public health concern because consumers are bringing these resistant bacteria into the kitchen. More generally, any use of antibiotics for animals, has the potential to dilute the effectiveness of antibiotics in human medicine.
As I have reported previously, FDA researchers recently confirmed my concerns about antibiotics use in farmed shrimp from Southeast Asia (Nawaz et al., 2012, Tran et al., 2011), although they stopped short of describing the implications for consumers or for informing policy.
Some might argue that simply cooking shrimp would kill the harmful bacteria, and they are correct. But it does not solve the underlying issue of the proliferation of antibiotic resistant bacteria. In addition, today we are seeing a trend among producers selling pre-cooked or “ready-to-eat” shrimp.
In a study of pre-cooked frozen shrimp imported from India and Thailand, researchers found plenty of drug resistant bacteria. These findings by Mississippi State University researchers (Duran and Marshall et al., 2005) call into question the safety of prepared shrimp. It seems counter-intuitive, but to be safe, consumers may consider cooking pre-cooked shrimp.
What about domestic shrimp? For domestic shrimp, 200 million pounds are wild-caught mostly in the Gulf Coast region, and 10 million pounds are farm-raised, mainly from farms in Texas, but also one farm in Maryland. Few studies have been conducted that compare domestic shrimp to imported shrimp, but I suspect the levels of antibiotic resistance bacteria would be lower in domestic products. I think this is certainly an area where further work is needed.
Currently, the best way to know the quality of shrimp you eat is to check the label for third-party farm auditors such as Quality Certification Services or Global Aquaculture Alliance Best Aquaculture Practices, but certainly more consumer-level information is needed. Seafood purchasers also have third-party auditors, like GLOBALGAP, but these labels are often not passed on to consumers at restaurants or institutional settings.
Consumers groups like Food and Water Watch and Monterey Bay Aquarium recommend purchasing domestic, wild-caught shrimp, or domestic farm-raised shrimp from “closed-system” farms where water and waste is controlled onsite.