Proceedings of the Third World Fisheries Congress: Feeding the World with Fish in the Next Millenium—The Balance between Production and Environment

Ensuring Seafood Safety and Identity

Iciar Martinez, David James


Lightly processed seafoods have a more positive effect on human health than cooked or refined products (E. O. Elvevoll, Norwegian Institute of Fisheries and Aquaculture, personal communication), but constitute a higher risk: botulism, listeriosis, and cholera are more frequently associated with smoked, fermented, salted, and pickled seafood consumed without further cooking (Huss 1994).

About half of the food-borne infections remain unrecognized because of inadequate diagnostic methods. The relevance of viruses was not suspected until the advent of sensitive molecular detection techniques in the 1990s. Shellfish are the primary source, and they are high risk because they are filter feeders and usually are consumed whole and raw or lightly cooked. Shellfish harvested in contaminated areas may carry a mixture of viruses, and consumers may be simultaneously contaminated with more than one viral strain. The need to reevaluate the method used to control viral contamination is illustrated by the fact that in many outbreaks, the harvesting areas, treatment processes, and products sold to consumers were in compliance with current regulatory requirements established by the countries involved (Lees 2000).

Pathogenic bacteria associated with seafood-borne diseases (SBDs) are those naturally found in the aquatic environment (i.e., Listeria monocytogenes) and mesophilic bacteria contaminating the environment from animal reservoirs (i.e., Salmonella) (Huss 1994). Listeria monocytogenes has rarely been detected in products from tropical areas, where Salmonella is the main hazard. The death rate of listeriosis ranges from 23 to 51%, and 85– 95% of cases are food-borne. Seafood is thought to have caused only one outbreak, although it has been found in about 25% of products tested (Ryser and Marth 1991). Classical microbiological, immunologic, and molecular biological techniques are well developed for most bacterial hazards, and many human pathogens have been fully sequenced. Recently, it has become obvious that it is also necessary to identify genes for resistance to antibiotics, disinfectants, or both.

Trematode parasites are associated with freshwater fish. About 700 million people are considered to be at risk of contracting food-borne trematode infections (FBTIs), and 40 million to 50 million people are believed to be infected by one or more species (Garcia and Leiva Moreno 2000). FBTIs are particularly prevalent in East and Southeast Asia. Human infection results from ingestion of inadequately processed fish that harbor viable metacercariae. Parasite detection, based on the microscopic examination of specimens for eggs, is fastidious and complicated. Easier, reliable, and faster techniques are needed (WHO 1995).

Aquaculture may be a relevant factor for the possible spread of SBDs and FBTIs: 85% of the total fish is farmed in developing countries (almost 68% in China, then 6.45% in India), and about 90% of the total production is freshwater fish (Brown 2000). Because about 75% of the world stocks for which data are available are fully exploited (47%), overfished (18%), depleted (9%), or recovering (1%), alternative raw materials must come from aquaculture or exploitable grounds (Garcia and Leiva Moreno 2000). As a result, customers face increasing fraud due to substitution.