4 IDENTIFICATION OF HAZARDS IN SEAFOOD

4.1 Statistics on seafood-borne diseases (Lone Gram)

The true incidence of diseases transmitted by foods is not known. There are many reasons for this. In most countries there is no obligation to report on food borne diseases to public health authorities. In the few countries which have a reporting system there is severe underreporting. It has been estimated that as few as 1% of the actual cases of food-borne diseases are reported (Mossel, 1982). This is because neither the victim nor the physician are aware of the etiological role of foods. Furthermore, the food responsible is often not available for analysis and the true vehicle for the disease agent is not identified. The statistics presented should therefore be used as indications of trends and areas of concern.

The Centre for Disease Control (CDC) in Atlanta compiles all information on food-borne disease in the US. Between 1993 and 1997, 2 751 outbreaks involving 86 000 people were reported (Table 4.1). In only 1/3 of the outbreaks was a food vehicle identified. Seafoods were often implicated in disease but did not, as opposed to some other foods, result in deaths. As products such as meat and poultry are consumed in much larger amounts, the number of cases traced to seafood is rather alarming.

Table 4.1 Food implicated in food-borne disease in the US 1993-1997 (modified from Olsen et al., 2000).

In the USA, the etiological agent was identified in approximately 50% of the outbreaks caused by shellfish (both molluscan shellfish and crustaceans) whereas the cause of disease was identified in almost 90% of the outbreaks related to fish (Olsen et al., 2000). It is likely that several of the outbreaks caused by molluscan shellfish for which a cause was not identified were indeed viral. This could, in part, be explained by the lack of methods for detecting foodborne virus.

Outbreak Alert (CSPI, 2001) lists outbreaks/cases in which an etiological agent has been identified. From 1990 to 1998, more than 5 000 cases of seafood borne diseases were linked to a cause. Molluscan shellfish, although being responsible for a much lower number of outbreaks than fish, caused the double the number of cases.

Table 4.2 Number of outbreaks and cases related to seafood in the US from 1990 to 1998. Listed are only outbreaks for which an etiological agent has been identified (CSPI, 2001).

A total of 1 661 cases were caused by consumption of "fish" (Table 4.2). The majority of cases were caused by scombroid or ciguatera intoxication (Table 4.3). Also, several outbreaks of botulism were recorded as were more than 300 cases of salmonellosis. These outbreaks were, however, not universally distributed. Thus the vast majority of ciguatera outbreak occurred in Hawaii or in Florida where the consumption of tropical reef fish is high. Similarly, three fourth of the botulism cases were registered in Alaska and were attributed to the consumption of various fermented seafood preparations.

Etiological agents were identified in more than 3 000 cases of disease caused by molluscan shellfish (Table 4.4). Bacteria indigenous to the marine environment, e.g. Vibrio spp. did cause several cases, but organisms from the human-animal reservoir were the dominant causes. This included the major cause of disease, viral gastroenteritis, in particular Norwalk virus, but also Salmonella and Shigella were responsible for outbreaks.

Shellfish other than molluscan shellfish also caused disease. Etiological agents were identified in 146 cases of food-borne disease from 1990 to 1998 (CPIS, 2001). These were caused by Norwalk virus (one outbreak, 46 cases), Salmonella (one outbreak, 45 cases), Campylobacter (one outbreak 32 cases), Vibrio parahaemolyticus (one outbreak, 7 cases), Staphylococcus aureus (one outbreak, two cases) and 3 outbreaks of V. cholerae (14 cases).

Table 4.3 Seafood borne diseases traced to "fish" in the USA from 1990 to 1998. Outbreaks and cases for which the etiological agent has been identified (CSPI, 2001).

1. One outbreak in New Jersey (salted whitefish) and two in California (both home-canned tuna)

2. Haff disease is an unexplained rhabdomyolysis (the breakdown of muscle fibres with leakage of potentially toxic cellular contents into the systemic circulation) in a person who ate fish in the 24 hours before onset of illness.

Table 4.4 Seafood borne diseases traced to "molluscan shellfish" in the USA from 1990 to 1998. Outbreaks and cases for which the etiological agent has been identified (CSPI, 2001).

Between 1992 and 1999, 1 425 foodborne outbreaks of Infectious Intestinal Disease (IDD) were reported in the UK (Gillespie et al,. 2001). This represented one third of all infectious intestinal disease outbreaks reported (Table 4.5). Ten percent of the 1 425 foodborne outbreaks were caused by seafoods. Of the 148 outbreaks traced to seafood, 47% were traced to finfish and most were caused by scombroid toxin. These outbreaks typically occurred in the warm summer months. Molluscan shellfish were responsible for one third (36%) of the outbreaks and these were typically associated with viral infections from live oysters. The last major cluster was outbreaks caused by crustaceans (11%) which typically involved viral pathogens or salmonellae. Salmonellae were also involved in four outbreaks traced to finfish.

Table 4.5 Etiological agents of foodborne outbreaks in UK associated with seafood (Gillespie et al., 2001).

1 Total number of reported intestinal disease outbreaks

4.2 Detentions and rejections of seafood in international trade (Lone Gram/Lahsen Ababouch)

Seafoods constitute a major commodity in international trade and despite the introduction of quality assurance schemes in the sector, various sampling and control analysis of end products are carried out, particularly of imported foods at port of entry. Section 4.1 on seafood borne diseases gives indications of the health consequences of biological hazards, but results from import controls may also point to areas of concern.

In the USA, the Food, Drug and Cosmetic Act authorizes FDA to detain a regulated item that appears to be out of compliance with the act (FDA, 2002). This covers a vast range of commodities: foods, beverages, drugs, cosmetics, animal feed, chemicals, orthopaedic equipment etc. Each month, the import refusal report (IRR) is published based on data generated by the FDA's Operational and Administrative Import Support (OASIS). The data are available by country or by product commodity. Approximately 1/10 of the refused products are seafood products (Table 4.6).

The most common reason for import refusal is "filthy" which describes that the product appears to consist in whole or in part of a filthy, putrid or decomposed substance. Although details are not given for the individual products, it is assumed that microbial spoilage is the major reason for the refusal. Second in terms of rejection reason is the detection of Salmonella. Both cooked, ready-to-eat products and raw, frozen products are rejected if Salmonella is detected. Although Salmonella has its niche in the gastrointestinal tract of birds and mammals, it is a common bacterium in ponds in tropical areas and its detection may not indicate hygienic failure. Whether or not the detection in raw foods constitute a health hazard is debatable.

The category "other" covers a vast range of different reasons such as mis-labelling, lack of description of the process, or lack of verification of a HACCP plan.

Table 4.6 Seafood import refusals by US FDA from July 2001 to June 2002 (FDA, 2002).

1. Number of rejections where "filthy" is stated as a reason. Note that for some products several reasons, e.g. both "filthy" and "Salmonella" are given as reason for rejection.

The European Commission is operating a Rapid Alert system for foodstuffs. The system is used to inform Member States about problems or risks concerning foods which do not meet food safety requirements. The legal basis for the system is Council decision 92/59/EEC (EC, 1992) on general product safety. The principal objective is to prevent the placement on or the recall from the community market foodstuffs which pose a serious risk to the health of the consumer. Member States notify the Commission when

• a foodstuff poses a serious risk to the health and safety of consumers, and

• the probability that the foodstuff is on the market in another Member State.

The data from 1999 were compiled by Huss (unpublished) who concluded that in 1999, 107 seafood products were involved in Rapid Alerts (out of 295 in total). The main products and the main reasons for the Alerts were: chilled and frozen fish (or fish products) were implicated in 75 Alerts. The reason was primarily the presence of pathogenic bacteria (Vibrio spp., Salmonella, Listeria monocytogenes, Staphylococcus, Enterobacteriaceae, "aerobic mesophiles"), but also a number of chemical dangers were listed (heavy metals, pesticide-residues) shrimp, cray-fish tails, crab-tails (without specification of whether they were raw or cooked) were implicated in 30 Alerts, and the reason was always the presence of pathogenic bacteria (pathogenic Vibrio spp., Salmonella, Staphylococcus) tuna-fish products (canned, frozen or fresh) were involved in 6 Alerts: too high content of histamine (3), mercury (1) or presence of Salmonella or "aerobic mesophiles" detection of biotoxins, viruses or indicator bacteria (faecal coliforms, E.coli) in bivalve molluscs (8) presence of pathogenic bacteria in a number of un-specified seafood.

In an ongoing study, Ababouch and Gandini (unpublished) analysed the EU Rapid Alert System data of interest to Third Countries, i.e. non EU countries exporting fish and fishery products to the EU member states. The analysis encompassed the period from January 1999 to June 2002 (Table 4.7).

These data indicate that the number of alerts has increased steadily during the period January 1999 - December 2001 and basically exploded in 2002. The initial steady increase and the explosion of alerts in 2002 are due to several concurrent facts:

• The alert system has become generalized and fully operational only during the last 12 or 18 months, indicating some underreporting in the initial phase;

• Several safety concerns have emerged during the period 2001-2002 which triggered several additional controls at the entry point to the EU, e.g. analysis of Vibrio, analysis of antibiotic residues and other chemical pollutants (polycyclic aromatic hydrocarbons), following the enacting of recent EU regulations to monitor these residues in fish and fishery products marketed in the EU;

Regarding the cause of rejection/detention (Table 4.7), chemical and drug residues (46.4%), followed by microbial contaminants (39.7%) were the main causes for alert during the period 1999-2002. The majority of alerts because of chemical and veterinary drugs residues (74.4%) occurred recently in 2002, with chloramphenicol and nitrofurans representing respectively 54% and 24.5% of the alerts caused by chemical hazards and 39.6% and 18% of the total. Histamine and parasites caused the lowest rates of alerts, respectively 1.3% and 4%;

For microbial contaminants, there was a decrease (from 59.3 % in 1999 to 41% in 2001) of alerts due to the presence of indicator organisms and an increase (from 40.1 % in 1999 to 59.2 % in 2001) of alerts because of the presence of indigenous organisms, especially Vibrios. The former indicates improvement in the sanitary and hygienic conditions in handling and processing fish in their countries, probably as a result of the gradual implementation of GHP/GMP and HACCP. The latter reflects more recent decisions of the EU to analyse for indigenous microorganisms, especially Vibrio species while awaiting the results of risk assessments of Vibrios in seafood. In the meantime, the temporary EU decisions have led to rejections and detention of consignments that were probably safe to consume and have led to economic losses by exporters.

In fact, a risk assessment commissioned in 2001 by the European Commission (EC, 2001) concluded that:

i) the practice of judging seafood exclusively based on total Vibrio counts as indicative for the presence of pathogenic Vibrios is not appropriate and should be discontinued.

ii) the practice of judging seafood exclusively based on total V. Paraheamolyticus counts without consideration of the virulence factors (TDH/TRH (or tdh/trh) is not appropriate and should be discontinued;

iii) currently available scientific data do not support setting specific standards or microbiological criteria for V. Vulnificus and V. Parahaemolyticus in seafood. Codes of practice should be established to ensure that GHP has been applied.

Table 4.7 Causes of rejection/detention of seafood imported into the EU during the period January 1999 - June 2002 (Ababouch and Gandini, unpublished)

1. DSP
2. One cestode

By region, exporting countries from Asia accounted for 69.8% of the alert cases, followed by Africa (17.8%), the Americas (8.8%), Europe (non-EU) (2.7%) and Oceania (0.9%). This does not reflect the volume of exports by region, which amounted in 2000 for Asia to 14.7 % of the total export from third countries, 19.9% for Africa, 22.7% for the Americas (5.5% for North America and 17.2% for Latin America). These data indicate a need for improving further the sanitary conditions in Africa and Asia throughout the food chain from fish harvesting to export. In addition, there is an urgent need to improve sanitary conditions in aquaculture, especially by generalizing the application of Good Aquaculture Practices and a strict control on the use of banned drugs such chloramphenicol. These drugs banned for use in aquaculture and animal husbandry are becoming a significant health concern in major markets of Europe and the USA. Obviously, Asia, which produces around 89% of the world aquaculture fish is concerned at the highest level.

References

CSPI (Centre for Science in the Public Interest) 2001. Outbreak Alert. Closing the Gaps in our Federal Food-Safety Net. CSPI, Washington DC, USA.

EC (European Commission) 1992. Council Directive 92/59/EEC of 29 June 1992 on general product safety. Official Journal of the European Communities L. 228, 11/08/1992, p. 0024-NBNB

EC (European Commission) 2001. Opinion of the Scientific Committee on veterinary measures relating to public health on Vibrio vulnificus and Vibrio parahaemolyticus (in raw and undercooked seafood). Report adopted 20 September 2001. Health and Consumer Protection Directorate General. 64 Pages.

FDA (Food and Drug Administration) 2002. Introduction to FDA's Import Refusal Report (IRR). http://www.fda.gov./ora.oasis/ora_oasis_ref_intro.html

Gillespie, I.A., G.K. Adak, S.J. O-Brien, M.M. Brett and F.J. Bolton 2001. general outbreaks of infectious intestinal disease associated with fish and shellfish, England and Wales, 1992-1999. Communicable Disease and Public Health 4, 117-123.

Mossel, D.A.A. 1982. Microbiology of Foods. University of Utrecht. Faculty of Veterinary Medicine, Bittshact 172, Utrecht, The Netherlands.

Olsen, S.J., L.C. MacKinnon, J.S. Goulding, N.H. Bean and L. Slutsker 2000. Surveillance for foodborne-disease outbreaks - United States, 1993-1997. Report CDC Surveillance Summary. Morbidity and Mortality Weekly 49,1-62.