Nature

Crayfish is a popular food source as it has an appealing taste and good balance of nutrition, with high levels of protein, low levels of fat and a low number of calories; therefore, it has become the most widely cultured freshwater shellfish species (1, 2) . The largest consumers of seafood are China, Japan, and North America (2).

The family Cambaridae includes the species Procambarus clarkii, or red swamp crayfish, which is native to northern Mexico and southern United States. The main sources of fresh, frozen or processed foodstuffs containing red swamp crayfish, which are consumed either raw or cooked, are from China and the United States (3, 4). Over 2 million tons of crayfish were produced in 2019, equal to an economic value of more than $18 billion US dollars (4).

The family Parastacidae includes another species of crayfish: the Cherax quadricarinatus, also known as the red claw crayfish, which is indigenous to Australia. Primarily produced in Australia and Malaysia, C. quadricarinatus is exported across the world, particularly to Asian countries. In 2019, its production reached 0.17 million tons, equal to an economic value of $2.1 million US dollars (4).

Taxonomy

Crustaceans fall within the classification of arthropods, which includes over 50,000 species of shrimps, prawns, lobsters, crayfish and barnacles (3).

Table adapted (3, 9).

Over 20 allergens have been identified in crayfish (9)

Three key crayfish allergens have been thoroughly characterized; tropomyosin (TM), arginine kinase (AK), and sarcoplasmic calcium-binding protein (SCP). TM allergen occurs in many different types of seafood, including shrimp, lobster, crab and mollusks, and has been identified as a major allergen of crayfish; TM is a heat stable myofibrillar protein (2). TM has been identified in raw and boiled samples of C. quadricarinatus (4). TM may undergo a change in secondary structures, which could increase antibody recognition, as a result of high temperature treatment (4). AK is another major allergen of crayfish, and is one of the main cross-reactive allergens in crustaceans; it is a 40 kDa myosinogen protein(2). AK has been identified in raw samples of P. clarkii (4). The third allergen, SCP, is also a shrimp allergen found in white leg Pacific shrimp (Litopenaeus vannamei) and the black tiger prawn (Penaeus monodon); SCP has three subunits and three 22 kDa isoforms, all of which are allergy inducing (2).

Further allergens have also been identified, including myosin light chain 1, or MLC1, and triosephosphate isomerase (2, 10). MLC1 is more resistant to gastric digestion than intestinal digestion, enabling it to preserve immunological activity (2).

Cross-reactivity

Cross-reactivity has been identified between shrimp, crab, lobster and crayfish allergens to a high level (6). Also, reports have emerged regarding cross-reactivity between shellfish and insects; this is likely due to both animals belonging to the Arthropoda phylum (1).

Tropomyosin is regarded as a cross-reactive allergen in shellfish (1) TM from C. quadricarinatus has demonstrated high levels of sequence homology of 95.4–99.3% with other species of freshwater crustaceans, including Procambarus clarkii, Macrobrachium rosenbergii and Macrobrachium lanchesteri (4).

Cross-reactivity has been identified in MLC from crayfish by investigating reactivity with rabbit IgG. Furthermore, crayfish myofibrillar protein was shown to inhibit IgE binding by MLC from crayfish (1)