Molluscan shellfish

Coupled with successful primary prevention are ongoing monitoring programs for the organisms and their toxins, both in the environment and in the seafood. The molluscan shellfish (i.e., oysters, clams, mussels, and scallops) are the species associated with shellfish poisonings. The absence of characteristics such as abnormal taste, smell, or appearance precludes sensory inspection for these toxins. Instead, ensuring seafood safety relies on testing seawater and the seafood itself The assays used to detect toxins in seafood have evolved as analytic methods and instrumentation have improved. The American Public... 

Molluscan shellfish play an important role in human nutrition and the world economy (Wild and Lehrer, 2005). Table 4.2 provides data on the worldwide production/catch of various molluscan shellfish species for 2005. The most widely available species are oyster, squid, clam, mussel, and scallop. Aquaculture has become an important contributor to the production of molluscan shellfish with the exception of the cephalopods. However, the popularity and frequency of consumption of various molluscan shellfish varies widely across various countries and cultures. Accurate information on comparative consumption patterns for molluscan shellfish in various countries does not exist. Molluscan shellfish are consumed as freshly cooked or even raw seafood items particularly in coastal communities. But mollusks also are consumed as processed foods in a variety of forms. 

The importance of molluscan shellfish allergy is increasingly recognized. The European Union recently added molluscan shellfish to the list of most commonly allergenic foods in Europe (EESA, 2006). Although not knovm... 

TABLE 4.2 Worldwide production and catch of molluscan shellfish — 2005... 

The prevalence of allergies fo specific foods is unknown for the most part. Good estimates exist of the prevalence of milk allergy in infancy (Hosf and Halken, 1990) and peanut and tree nut allergy throughout the life span (Sicherer et ah, 1999). However, the prevalence of allergies to seafoods including molluscan shellfish is not precisely known. 

Sicherer et ah (2004) conducted a nationwide random telephone survey of the prevalence of seafood allergies in the United States and a standardized questioimaire. Responses were categorized on the basis of convincing symptoms and self-reported physician confirmation of the allergy. The survey involved 14,948 individuals with 67 reporting reactions to molluscan shellfish including scallops, clams, oysters, and mussels. The self-reported prevalence in this study population was 0.4%. 

Ranee et al. (2005) conducted a questionnaire-based survey of food allergy in 2716 school children in France. Four cases of molluscan shellfish allergy were reported to mussels, snails, and oysters among this group. Thus, the self-reported prevalence of molluscan shellfish allergy in this population of children was 0.15%. 

These two surveys are in reasonably good agreement regarding prevalence estimates for molluscan shellfish allergy. That is especially true since all the ages were included in the surveyed population of Sicherer et al. (2004) while only children were involved in the French survey (Ranee et ah, 2005). Hypothetically, sensitization to molluscan shellfish might develop later in life than for other foods because of the infrequent consumption pattern. 

In another Spanish study, Crespo et al. (1995) evaluated 355 children on the basis of clinical history, skin prick tests (SPTs), and specific serum IgE to mollusks. Allergies to molluscan shellfish were noted in 10 of these children or 2.8%. However, mollusks caused 1.6% of 608 allergic reactions among this group of children. 

The number of sfudies estimating the comparative prevalence of molluscan shellfish allergy is limited. The frequency of consumption of molluscan shellfish mighf be higher in some of the locales where such studies have been performed. Clearly, more comparative clinical data would be helpful. However, the molluscan shellfish certainly seem to be a comparatively common allergenic food in some locales and among some populations. 

Individualistic adverse reactions to foods can occur through several different types of mechanisms (Taylor and Hefle, 2001). True allergic reactions can include both IgE-mediated immediate hypersensitivity reactions and cell-mediated delayed h)q5ersensitivity reactions (Taylor and Hefle, 2001). However, only IgE-mediafed reactions have been documented to occur with ingestion of molluscan shellfish in sensifive individuals. 

While all humans have IgE antibodies fhaf are involved in defense against parasitic infections, only humans who are predisposed to the development of allergies will produce IgE antibodies upon exposure fo certain protein allergens present in their environment including their diet. Only a few of the many proteins found in foods are capable of sfimulating the production of specific IgE antibodies in susceptible individuals (Taylor, 2002). With molluscan shellfish, only one, or perhaps a few, of the numerous proteins is known to provoke the production of IgE antibodies that specifically recognize one or more species of molluscan shellfish. 

---