November 18, 2009
Farmed catfish made news in November as Alabama Agriculture and Industries Commissioner Ron Sparks announced a ban on all untested fish from Vietnam and China due to antibiotic drug residues detected in imported catfish from those countries (Associate Press). Catfish from Vietnam (i.e. basa, tra, or pangasius all called “Vietnamese catfish”) and China’s channel catfish contained residues of fluoroquinolones, a group of antibiotics prohibited by the FDA in fish or seafood.
Though catfish may look cute, aquaculture-raised channel catfish are big business in the Southeast United States fetching over $400 million in 2003 and accounting for 46% of the value of all domestic aquaculture (Miss State Extension Service). In 2006, the US produced about 560 million tons of catfish, compared to about 28 million tons of imported catfish from Vietnam and China in the same year (Associated Press), which is beginning to create a rivalry between US producers and imports.
channel catfish :: wikimedia commons
The recent ban on imported Vietnamese and Chinese catfish in Alabama could represent a move to regain control of the US catfish market. The Catfish Farmers of America have taken out advertisements in the Washington Post and Politico urging Congress to improve testing of imported fish. Reading between the line in catfish industry statements, it is hard to tell whether the true motivation is consumer safety (due to exposure to antimicrobial residues in fish fillets) or protecting domestic catfish market share— or both (Associated Press).
There are potential human health risks from antibiotics and antimicrobial residuals in fish and fish feed (Sapkota et al., 2004). Dosing fish with antibiotics is done for therapy, preventive reasons, or for growth promotion. The main concern is that antibiotics used for humans, like fluoroquinolones, when used in aquaculture may induce antibiotic-resistance in pathogenic bacteria that can cause potentially untreatable human diseases. Consuming antibiotics or their residues in fish meat could be harmful as well. Dr. Pilar Hernandez Serrano urges caution in a recent FAO sponsored paper entitled Responsible Use of Antibiotics in Aquaculture saying “the indiscriminate use of antibiotics for veterinary purposes has increasingly become a matter of public concern.”
Antimicrobial residues are not uncommon in aquaculture products— FDA reported to Congress on November 20, 2008 that between 2004 and 2007, 7.2% of all tested seafood samples were positive for antimicrobials (FDA). In the same report, fluoroquinolones, like those in the recent catfish samples, were detected in 12 samples of basa, 6 other samples of catfish, and sample of both grouper and tilapia over the 4 yr period. Other antimicrobials FDA reported detecting in shrimp and/or fish samples include chloramphenicol, nitrofurans, malachite green, quinolones, and crystal violet.
With only around 2% of all fish and seafood tested in the US (NMFS), it is likely that products with antibiotic residuals and antibiotic resistant bacteria enters US markets and become part of the estimated +11 lbs per year of fish and shellfish that the average American eats (EPA Exposure Factors Handbook Ch10).
Some questions that arise during these types of fish bans are:
- What are the public health risks from consuming catfish or other seafood products that contain antimicrobial residues or antimicrobial resistant bacteria?
- Is the current testing methodology and testing frequency enough to adequately protect the public?
- Would a mandatory reporting system for antimicrobials and other amendments to fish feed improve government oversight?
- What are the environmental impacts of farming catfish in Vietnam, China, and Southeast US?
Hopefully, competition for the US seafood market may provide just the right incentives for much needed improvements in quality control of imported and domestic aquaculture, and industry transparency with regards to antimicrobials in fish feed.
– Dave Love