Seafood Safety: Down on the Farm
By Brett Koonse Series Editor: Carrie Ainsworth
Worldwide, the “daily catch” means much more than just the type of fish that is being offered at seafood restaurants. More than 200 million people rely on their daily catch as a primary source of income. Seafood is an essential part of the diet in the developing world, where one in five people depend on it as their principal source of protein.
Unfortunately, over 70% of the world’s fish species are either fully exploited or depleted, according to the United Nations Food and Agriculture Organization (FAO) estimates. In the future, more and more fish and shellfish will be obtained from what is known as aquaculture, to meet the growing demand for seafood that “hunting and gathering” fish cannot provide.
Aquaculture, or fish farming, is the science and art of growing seafood such as catfish, salmon, oysters, or shrimp, under controlled conditions in ponds on land or in pens or nets in the ocean. It is the fastest growing sector of the world food economy. In fact, over the last two decades, aquaculture has grown by more than 10 percent a year and currently accounts for 52 percent of all fish production worldwide. China, where aquaculture has been practiced since 2,500 BC, is the largest aquaculture producer in the world, accounting for 70% of the total quantity and 55% of the total value of aquacultured seafood bought and sold around the world.
Aquaculture is advancing as an industry. Just 30 years ago, when modern aquaculture technology was coming into its own, farmers had to invest most of their time and energy into growing and keeping their fish alive. The industry has matured to the point of successfully growing a wide range of seafood products that can compete against wild caught fish while at the same time addressing the environmental concerns that once plagued the industry. In order to advance further, additional steps need to be taken. Aquaculture farm management needs to become an integral part of the farm-to-table food safety continuum.
U.S. Seafood Consumption and Importation
In the United States, seafood consumption has risen steadily to a record 16.6 pounds per person per year. About 80 percent of this seafood is imported from at least 62 countries (mostly developing countries). Forty percent of that seafood comes from aquaculture operations. China, with its large and expanding aquaculture industry, may soon bypass Canada and Thailand to become the largest exporter of seafood into the U.S.
Three of the most popular seafood items are also three of the top aquaculture imports: shrimp, salmon and tilapia. Together, they represented more than 2 billion pounds of seafood imported into the U.S. in 2004. It is estimated that 90 percent of shrimp, the number one seafood consumed in the U.S., is imported, and 75 percent of salmon, the third most consumed seafood, is imported.
Figure 1 shows the growing disparity between how much seafood is harvested in the U.S. and how much seafood will need to be imported to meet the projected growing demand.
Food Safety and Aquaculture
By and large, all seafood, whether caught in the open ocean or aquacultured, is considered some of the most safe and nutritious food available. However, there are food safety hazards associated with seafood and the hazards for raw aquaculture products are different than those for raw seafood caught in the open ocean. The two main hazards associated with imported aquacultured products consumed in the U.S. are residues of unapproved drugs and contamination from pathogens, such as Salmonella. The origins of these hazards are unique to aquacultured raw products because they usually originate at the farm site and may remain in or on the product through the normal washing, sorting and packing that is done at the primary processing step.
Let’s take a closer look at these two potential hazards associated with aquacultured products that are imported and consumed in the U.S.
Salmonella. Like other raw animal products, it is generally understood that seafood has the potential to be contaminated with Salmonella. From 1990 to 1998, the U.S. Food and Drug Administration (FDA) tested 11,312 raw seafood samples for Salmonella, 94 percent of which were from imports. The incidence of Salmonella differed between product of domestic and import origin. Nearly 10 percent of the import and 2.8 percent of the domestic raw seafood was found to contain Salmonella. The higher proportion of imported products sampled is a result of FDA’s increased emphasis on targeting countries or products (e.g., shrimp) where past sampling has indicated a higher probability of finding Salmonella and may not represent U.S. seafood in general.
Aquaculture products sampled directly from inland ponds have been shown to have a high incidence of Salmonella. For example, a study in Japan found Salmonella in 26 percent of aquaculture eel samples. A study of shrimp farms in India found Salmonella in 37.5 percent of the samples and a study in Thailand found it in 16 percent of the samples.[2,3]
Aquacultured products may also be contaminated with Salmonella on the farm after harvesting. In a recent study that FDA conducted on shrimp farms in six countries, 13.5 percent of the processing water (the water mixed with ice to cool the product down after harvest) samples that were analyzed contained Salmonella.
The presence of Salmonella in seafood products does present a food safety risk. In 2000, a salmonellosis outbreak occurred on a commercial cruise ship that was attributed to aquacultured shrimp from Vietnam.
At one time, it was thought that Salmonella may be part of the natural flora of inland aquaculture environments, or inherently present in the ponds where the fish or shrimp are raised. But a study conducted by FDA in 2005 showed that the occurrence of Salmonella bacteria in a shrimp farm’s aquaculture operation is related to the concentration of fecal bacteria in the source water (the water put into the ponds to grow the shrimp) and the shrimp pond water. An FDA article titled “Salmonella and the Sanitary Quality of Aquacultured Shrimp,” which appeared in The Journal of Food Protection, concluded that the presence of Salmonella is not naturally occurring, does not generally come from bird droppings, and is avoidable.
Aquacultured shrimp and tilapia may present a particular risk for bacterial foodborne diseases. They are often consumed only lightly cooked or even raw. An example of this is ceviche, an appetizer served at many South American and Mexican food restaurants. Traditionally, ceviche is made from raw shrimp or from a raw mild white fish such as tilapia.
So, the question is: Why is Salmonella found in aquacultured seafood products, when bacteriological pathogens are not usually considered a problem in wild open-ocean seafood products? Inadequate food safety training and poor management practices on aquaculture farms in developing countries may be two of the reasons.
Unapproved Residues. Antibiotics and certain chemicals (e.g., malachite green, a toxic chemical primarily designed to be a dye that is used, among other things, to treat bacterial infections in fish) are commonly used in aquaculture mainly for therapeutic purposes. They are also used as prophylactic agents to help avoid bacterial or fungal outbreaks. While there is only one drug (Formalin-F) currently approved for use on shrimp in the U.S., a group of Swedish scientists reported in 2003 that on average, 13 different chemical and biological products were being used in shrimp ponds in Thailand. Specifically, they found 96 percent of the 76 shrimp farmers interviewed used at least one kind of pesticide or disinfectant (the most common include teaseed, chlorine, formalin and triclorfon); 74 percent of the farmers used one or more types of antibiotics (the most common group being fluoroquinolones, followed by tetracycline and sulfonamides); and 86 percent of the farmers used products containing microorganisms or probiotics.
Legitimate public health concerns exist about the use of unapproved or misused drug products in aquaculture. One concern is the risk of exposing consumers to potential or suspected carcinogens such as malachite green. Another is the presence of antibiotics that can be harmful at very low levels to susceptible individuals. An example of this is the antibiotic chloramphenicol, which has been linked to human aplastic anemia and has been detected in various aquacultured products from several countries.
A particular concern is that the indiscriminate use of unapproved antibiotics for aquaculture may contribute toward the increase of antimicrobial resistance in foodborne pathogens which may be transferred to humans. While most of the rising antimicrobial resistance problem is probably due to overuse and misuse by health care personnel and patients, some of the newly emerging resistant bacteria in animals are transmitted to humans. The World Health Organization concluded that resistance of these bacteria to classic treatment in humans is often a consequence of their use in agriculture, mainly via meat and other food of animal origin. This concern includes the use of antibiotics in aquaculture.
Jean-Yves D’Aoust, a research scientist with Health Canada, describes how the use of antibiotics and the potential for Salmonella to occur in aquacultured products may present a unique potential situation for a serious salmonellosis incident to occur. If a person consumed undercooked or cross-contaminated aquacultured seafood containing an ampicillin-resistent Salmonella spp. strain, a subsequent systemic infection could lead to a serious or even fatal outcome if a patient is treated with a traditional treatment of ampicillin. This treatment could prove detrimental because the antibiotic would not only reduce the number of competing microorganisms in the intestinal tract but would also facilitate the massive invasion and spread of the ampicillin-resistent Salmonella spp. in host tissues. If this situation is not discovered and the therapeutic regimen quickly changed, it could prove fatal.
The Effects on Trade and Resources
The FDA considers the presence of Salmonella or unapproved drug residues an adulterant in raw or cooked products. At any given time there could be hundreds of foreign seafood processors on FDA Import Alerts after their products have been found to contain Salmonella or an unapproved residue. This essentially means that every shipment from these processors will be automatically detained and denied entry into the U.S. until the importer provides evidence the products are Salmonella- or residue-free.
Therefore, the presence of Salmonella and unapproved drug residues not only presents a public health risk, but also requires the FDA and the seafood industry to spend considerable resources. Time and funding is spent sampling product, analyzing samples, reviewing records and storing product in an effort to minimize the exposure of Salmonella and unapproved drug residues to U.S. consumers.
To assure seafood safety around the world, governments and industry have traditionally applied recognized food safety guidelines or systems, such as Hazard Analysis and Critical Control Points (HACCP), Total Quality Management (TQM), or quality assurance (QA) programs at the processor or manufacturing point, but less often at the farm or source.
In 1995, FAO recognized that food safety hazards associated with aquaculture products originate at the farm level and developed the Code of Conduct for Responsible Fisheries, which advocates food safety and high quality for products from aquaculture. Article 9, “Aquaculture Development,” and in particular, the provisions for “Responsible Aquaculture at the Production Level” addresses the need for countries to promote that “fish farmers and their communities…develop responsible aquaculture management practices” and “ensure the food safety of aquaculture products.” This document is general in nature and does not include what responsible management practices are, how farmers can promote food safety, or how they should integrate food safety into their own farm management practices.
Some countries, such as Thailand, through their Department of Fisheries, have implemented certification programs to address environmental and food safety concerns about shrimp aquaculture farms. There are also private, non-governmental certification organizations which certify the presence of food safety standards, as well making sure that social and environmental controls are in place at shrimp aquaculture farms. Despite these efforts, there are no globally recognized guidelines, standards, preventive measures or training courses for aquaculture farmers who wish to ensure that their products do not become contaminated with pathogens or unapproved drugs.
Pilot Food Safety Program
The Joint Institute for Food Safety and Applied Nutrition (JIFSAN), a multi-disciplinary research and education institute established by the FDA and the University of Maryland, has gone a step further and intends to pilot a series of Good Aquaculture Practices (GAqPs) food safety programs. JIFSAN intends to pilot these programs to learn from the interaction with the local aquaculture industry, academia and governments about reducing the food safety risks associated with aquacultured seafood in order to develop a future comprehensive GAqP training course and teaching manual.
Once the courses have been piloted, the FDA will consider developing a GAqP guidance document for the aquaculture industry.
The comprehensive JIFSAN GAqP course will be an interactive “train-the-trainer” course, designed for aquaculture industry representatives, government farm assistance agents, and professional aquaculture consultants. It will cover what GAqPs are, what the food safety risks are, and most importantly, what preventive measures and corrective actions are available to reduce the risk that aquaculture products will be contaminated with pathogens, chemicals or unapproved antibiotics.
The GAqP course will include lectures, demonstrations and local production facility site visits and covers hatchery operations, production, harvesting, transportation, and primary processing. The course will also include instruction on how to avoid animal pathogenic viruses, effluent treatment options, and how to present a GAqP course to a variety of farmers (i.e., “mom and pop” type farms or large industrial farms) and how an industry association or government agency can evaluate how well a GAqP program is being implemented by an aquaculture farming community.
JIFSAN’s pilot programs will initially focus on inland aquaculture farming, such as shrimp, tilapia, eel, and catfish. The first pilot is scheduled to be held in Vietnam, Nov. 13-17, 2006.
Just as modern agriculture has provided a steady and safe supply of grains, vegetables and meat to an ever-increasing world population for hundreds of years, aquaculture, developed and managed with appropriate environmental safeguards and food safety controls, can be a source of healthy and sustainable seafood for the future.
Brett Koonse is Branch Chief, Programs and Enforcement, Office of Seafood (OS) Center for Food Safety and Applied Nutrition (CFSAN), U.S. Food and Drug Administration (FDA). He has worked in the area of seafood as a fisherman, biologist, regulator and researcher for almost 30 year,s including the past 17 with the U.S. FDA. In the last five years, he has visited hundreds of various aquaculture farms to interview farmers and to conduct aquaculture research in more than 16 different countries.
1. NOAA Press Release. Americans Told to Eat Seafood Twice Per Week for Optimal Health. 12-5-2005. nmfs.noaa.gov/docs/Conference
2. USDA Progress Report on Salmonella Testing of Raw Meat and Poultry Products, 1998–2005. fsis.usda.gov/Science/Progress_
3. Reilly, P.J.A, D.R. Twiddy, and R.S. Fuchs. 1992. Review of the Occurrence of Salmonella in Cultured Tropical Shrimp. FAO Fisheries Circular
4. Koonse, B. W. Burkhardt, S. Chirtel and G.P. Hoskin. 2005. Salmonella and the sanitary quality of aquacultured shrimp. J. Food Prot. Vol. 68, No. 12, Pages 2527-2532.
5. Graslund S., K. Holmstrom. and A. Wahlstrom. 2003. A field survey of chemicals and biological products used in shrimp farming. Marine Poll. Bull. 46: 81–90.
6. D’Aoust, J.Y. 1994. Salmonella and the international food trade. International Journal of Food Microbiology, 24, p. 11-31.