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|Route of Exposure||Ingestion|
|Source Material||Fish protein|
|Latin Name||Gadus morhua|
|Other Names||Atlantic Cod, Cod (Canada), Morue (France), Dorsch, Kabeljau (Germany)|
|Categories||Food Of Animal Origin, Fish|
Cod (family Gadidae) is an economically important fish distributed in the northwest Atlantic Ocean found in Canadian waters, Greenland, and North Carolina. It is a cold-water fish, which can survive in nearly freezing to 20oC temperature and found in both fresh and marine water. Cod protein content is usually between 15-20% of their body weight. In codfish, the major allergen is the muscle protein parvalbumin, which is a calcium-binding protein. Parvalbumin is also known as “Gad c 1”, and it is the first calcium-binding allergen characterized from codfish, which cannot be destroyed by heat or cooking. Hence, if the individual or sensitized person is exposed to the cod allergen through oral, nasal or occupational route, the allergen triggers an allergic reaction. Detection of codfish allergy is based on clinical history, skin prick test, and specific IgE and immunoblotting tests.
The codfish cross reactivity was closely related to mackerel (Perciformes), herring (Clupeiformes), and plaice (Pleuronectiformes). Also, cods parvalbumins (Gad c 1) cross react with parvalbumins from salmon (Sal s 1), and pollack (The c 1).
The Atlantic cod is an economically important marine fish which can attain ages of 20 years. Adult codfish has a large head and heavy-body. The snout is blunt and the lower jaw tip has a barbel on the dorsal side. Color varies with small spots and pale lateral line in their body. Their average weight is around 25-35 kg and they can grow up to a length of 130 cm. Sexual maturity occurs at a median age of around 1.7-2.3 years with lengths ranging from 32-41 cm (1).
The codfish is found in Canada that includes the east coast of Labrador, south of Cape Harrison, east Newfoundland, Flemish Cap, Grand Bank, Gulf of St. Lawrence and Scotian Shelf. Young stages in Atlantic where cod tends to be restricted around major spawning centers (1).
Table 1: Taxonomic tree of Codfish (2)
|Taxonomic tree of Codfish|
In codfish, fat is confined mainly to the liver; muscle blocks with tiny blood vessels separated by thin connective tissue. The amount of protein is usually between 15-20% of the body weight. Fat content varies greatly based on different seasons and is usually < 1% of the muscles, as shown in the following table (3).
Table 2: Chemical composition of cod flesh
|Specie||Water (%)||Fat (%)||Protein (%)||Energy value (Cal/lb)|
Prevalence rates of fish allergy are 0.7 % in the global population. Higher prevalence was observed in the pediatric groups and in long coastline countries with fish as a staple food and fish-processing industries (4). A cross-sectional, random telephonic national survey conducted in the USA reported 3.3% of the general population has a seafood allergy (5).
Cod tends to move in deeper, colder and saline water with increasing age. They are found on or near the bottom along rocky slopes and ledges in depth ranging from 40-130 m but rarely found at 200 m. Cod can survive temperature ranging from near freezing to 20°C. However, during the fall they are found in warmer temperatures compared to temperatures of < 10°C where they are usually found (1).
Cod is distributed in the northwest Atlantic Ocean from Greenland to Cape Hatteras in North Carolina. The density in the Gulf of St. Lawrence, Scotian Shelf Georges Bank, and the western Gulf of Maine are the highest (1).
The route of exposure is mainly an oral route through consumption, but touch and inhalation of fish and related products can as well trigger allergic reactions (6).
Detection of allergy is based on clinical history, skin prick test, specific IgE tests, histamine release test, and immunoblotting, followed by oral fish challenge. Serum IgE antibodies levels are estimated along with the clinical reactivity to predict fish allergy (7).
In cod allergic patients, incomplete digestion of cod can lead to anaphylaxis. While in non-allergic subjects, fish allergens are identified within 10 min and reach a peak in 1-2 hrs. after ingestion. Digestive enzymes cause protein fragmentation, which reduces biological activity. However, increasing pH to 3.0 for digestion leads to reactivity patterns comparable to undigested extracts (8).
Codfish allergy symptoms can affect single or multiple organs, ranging from mild to severe anaphylaxis. Clinical symptoms start in less than 1 min after fish exposure. This can lead to cutaneous (urticaria, angioedema), GI (oral allergy syndrome, laryngeal edema, spasm, diarrhea, vomiting), and respiratory (rhino-conjunctivitis, bronchospasm) and severe anaphylaxis in some cases (6).
Fish allergic individuals should strictly avoid fish in any form including fish-derived products (9).
In fish and amphibians, calcium-binding proteins (CBPs) are important food allergens. The first calcium-binding allergen characterized was parvalbumin from codfish (10). The most common allergen in codfish is a muscle protein (CBPs) called parvalbumin, also known as “Gad c 1”. It is a major allergen, extremely stable to heat, with a low-molecular-weight (10–12 kDa), commonly found in fish muscle (9).
Table 3: WHO/IUIS registered fish allergens (4)
|Fish Species||Allergen||Protein type|
|Gad c 1||β-parvalbumin|
Gad m 1
Gad m 2
Gad m 3
A study by Hensen in 1997, showed that all clinically codfish-sensitive adults have serological cross-reactivity to other fish species (7).
The parvalbumins from salmon (Sal s 1), pollack (The c 1) showed high identity indices with the amino acid sequence of cod (Gad c 1), which supports the cross-reactivity between these fish species (11). The identity indices of Gad c 1 amino acid sequence were similar to parvalbumins from Sal s 1 (68%) and the c 1 (62%), which highlights the cross-reactivity (11).
Author: Turacoz Healthcare Solutions
Reviewer: Dr. Fabio Iachetti
Last reviewed: October 2020