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Keywords:

  • asthma;
  • fish food;
  • Gammarus;
  • IgE

T he amphipod Gammarus shrimp, or freshwater shrimp, belongs to the Crustacea family Gammaridae. It is used in several European countries to produce pet-fish food. So far, sensitization to Gammarus has not been reported. Our patient, a plant electrician who worked in a fish-food factory, appeared to suffer from allergic asthma due to the dust of these shrimp occurring in the workplace.

The patient was a 29-year-old man. About 8 weeks after he had started working in a fish-food factory, he developed chest tightness, cough, and dyspnea with wheezing. These symptoms appeared regularly at times when he was working near the production areas where dried Gammarus shrimp were mixed and packed with other fish-food ingredients. Sometimes the symptom of dyspnea would last until noon of the following day. On weekends or holidays, the symptoms decreased or disappeared completely.

Skin prick testing with a standard series of 26 common inhalant allergens including herring, flounder, sole, cod, haddock, shrimp, and crab (ALK, Copenhagen, Denmark) revealed only sensitization to tree pollen. However, the patient showed a strong positive skin reaction to the extract of dried Gammarus, the product of the fish-food factory (wheal diameter ≥10 mm).

Positive IgE antibodies to the protein extract of Gammarus could be detected in the patient's serum (1.4 kU/l, RAST class 2) by the enzyme-linked allergosorbent test (EAST) with an Allergopharma RAST test kit (Allergopharma Joachim Ganzer KG, Reinbek, Germany). To prepare the solid-phase antigen, the dried Gammarus was extracted in 0.1 mol/l potassium phosphate buffer, pH 7.4. The proteins were then coupled onto paper disks at a protein concentration of 1 mg/ml. IgE binding to Gammarus extract in two control sera from unrelated subjects was not observed. Immunoblot of Gammarus extract was also performed by the method described previously ( 1). Protein staining after SDS–PAGE showed different bands in the range of 14 to >90 kDa. Immunostaining revealed a distinct IgE-binding band around the 80-kDa area ( Fig. 1). No IgE-binding was observed with control sera.

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Figure 1. SDS–PAGE result of Gammarus extract (lane 1) and IgE immunoblot analysis with subject's serum (lane 2), showing IgE binding to protein band at about 80 kDa. Lane M indicates protein markers.

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Specific IgE to Chi t 1-9 (hemoglobin allergens of the nonbiting midge Chironomus thummi thummi, another pet-fish food) was also detectable (1.0 kU/l).

The clinical examination revealed FEV1 of 76.4%, MEF75 of 55%, MEF50 of 46%, and MEF25 of 32% of the predicted values of Quanjer et al. ( 2). The patient also displayed an unspecific bronchial hyperreactivity in the methacholine challenge test (PD20=0.1 mg methacholine). An immediate asthmatic reaction occurred 30 min after an occupational-type inhalative challenge test in handling dried Gammarus shrimp (increase in sRt to more than 250% of the baseline value).

From the above test results, we concluded that the occupational exposure to the dust of dried Gammarus, as well as the type I sensitization to Gammarus shrimp, was the major cause of the asthma episode in our patient.

Allergic disorders such as asthma, allergic rhinitis, and bronchitis induced by occupational contact with pet-fish food among workers in the fish-food industry have been reported. The most frequently studied allergens in fish food are the hemoglobin molecules Chi t 1-9 of C. thummi thummi ( 3, 4). Several cases of sensitization to Daphnia spp. in aquarium keepers have also been described ( 5). There has been no report on type I sensitization to Gammarus shrimp due to occupational exposure.

According to the patient, about one-third of the staff of the same factory complained of respiratory symptoms upon exposure to dried Gammarus shrimp. Therefore, this case does not seem to be a single one. A similar sensitizing effect on fish fanciers using this product on a regular basis also cannot be excluded.

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Footnotes
  1. IgE-mediated asthma caused by occupational exposure to pet-fish food.