Common names: Daphnia, Daphnids, Water fleas
An occupational allergen, which may result in allergy symptoms in sensitised individuals.
Daphnia or "Water fleas" are among the most common crustaceans to be found in lakes, ponds and quiet streams. Daphnia belong to a group known as the Daphniidae or Daphnids (related to Freshwater and Brine shrimps); the terms Daphnia and Daphnids/Daphniidae are often used interchangeably. "Water fleas", on the other hand, is a name that can extend beyond the Daphnids to cyclops and cypridopsis species.
Worldwide, there are more than 150 known species of Daphnia, and there can also be great variation within species, depending on environmental conditions. Adult Daphnia range in size from half a millimetre to almost a centimetre. Daphnia are roughly kidney-shaped and almost transparent. They have a single compound eye and a simple eye called an ocellus, two doubly-branched antennae, and leaf-like limbs inside the carapace. They are able to reproduce asexually: the offspring are exact clones of the parent, but may develop differently. Multiple generations of females can be born in this way within a few weeks. During adverse environmental conditions, some eggs develop into males, and the females produce eggs that must be fertilised. These eggs turn into small embryos that then go into suspended animation, in brown/black saddle-shaped cases known as ephippia (“saddles”), which can even survive without water.
Twenty species may often be found in a single pond. Daphnia are a major food source for many kinds of fish, aquatic insect larvae and other invertebrates. They are extremely important in food chains. Some species are commonly used as food for aquarium fish.
No allergens have yet been characterised.
Cross-reactivity has been reported to occur among IgE-binding proteins from Anisakis, German cockroach (Blattella germanica), and Chironomus (red mosquito larvae). A strong association was also described among Atlantic shrimp (Pandalus borealis), Ascaris lumbricoides and Daphnia, but this could not be confirmed in laboratory studies (1).
Daphnia may uncommonly induce symptoms of occupational allergy, such as asthma, in sensitised individuals (2-4). An early study reported that Daphnia may be "one of the possible allergens in the pathogenesis of allergic forms of vasomotor rhinitis (5).
Occupational allergy to Daphnia occurs most commonly in live fish bait workers. Two workers in a fish food store who had occupational asthma to Daphnia were described. Type I hypersensitivity was confirmed by skin-specific IgE and bronchial provocation tests (6).
Seven cases of asthma, allergic rhinitis and bronchitis, induced by non-occupational contact with pet fish food, were described. The study pointed out that food for pet fish contains proteins of a variety of arthropod species (larvae and adult forms) – e.g., Chironomus, Daphnia, and Brine shrimps – as well as freshwater worms such as Tubifex, Enchytraea, etc.; but in this instance, it was sensitisation to Chironomus that manifested in most of the patients, and Daphnia was also known to be a specific allergen (7).
A 27-year-old patient who kept fish and suffered from asthma was shown to have strongly positive skin-specific IgE tests for Chironomus and Culex larvae, as well as several kinds of Crustacea species, such as Daphnia and Brine shrimps (8).
In 611 patients with extrinsic and intrinsic asthma, evaluated over a 6-year period as to the presence of an aquarium in their residence and whether they used fish food with dried Daphnia, 43 patients with atopic asthma and allergic rhinitis were shown to be exposed to Daphnia. Of these, 28 had high-positive skin-specific IgE tests to Daphnia extracts. On interrogation, all sensitised patients reported symptoms on exposure to dried Daphnia, information that was not spontaneously volunteered. After avoiding contact with Daphnia, all patients became symptom-free (9).
Contact dermatitis caused by Daphnia has been reported (10).
Compiled by Dr Harris Steinman, email@example.com
- Pascual CY, Crespo JF, San Martin S, Ornia N, Ortega N, et al. Cross-reactivity between IgE-binding proteins from Anisakis, German cockroach, and chironomids. Allergy 1997;52(5):514-20
- Popescu IG, Dragulescu I, Iota CG. Bronchial asthma caused by Daphnia P. [German] Allerg Asthma (Leipz) 1970;16(6):242-5.
- Mairesse M, Ledent C. Allergy and fishing activities. [French] Allerg Immunol (Paris) 2002;34(7):245-7.
- Ferranti A. Peculiar allergy produced by Daphnia pulex; preliminary note. [Undetermined Language] Arcisp S Anna Ferrara 1952;5(2):137-40.
- Prianichnikov GE. Daphnia as one of the possible allergens in the pathogenesis of allergic forms of vasomotor rhinitis. [Russian] Vestn Otorinolaringol 1965;27:25-7.
- Meister W. Professional asthma owing to Daphnia-allergy (author's transl). [German] Allerg Immunol (Leipz) 1978;24(3):191-3
- Knusel J, Wüthrich B. 'Aquarium allergy': fish food, another domestic allergen [German]. Schweiz Med Wochenschr 1983;113(18):658-62
- Dietschi R, Wüthrich B. 'Aquarium' allergy: bronchial asthma caused by polyvalent sensitization to various components in fish food [German]. Hautarzt 1987;38(3):160-1
- Meister W. Bronchial asthma following Daphnia allergy [German]. Z Erkr Atmungsorgane 1982;158(3):319-21
- Metzner HH. Contact dermatitis caused by Daphnia. [German] Dermatol Monatsschr 1985;171(8):523-4.