Green nimitti

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Blood worm i73

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Code: i72
Latin name: Cladotanytarsus lewisi
Source material: Whole insects and maggots
Family: Chironomidae
Common names: Green nimitti, Sudan fly

Insect

An insect, which may result in allergy symptoms in sensitised individuals.

Allergen Exposure

Green nimitti (Cladotanytarsus lewisi) is a non-biting midge that breeds in lakes, rivers and water reservoirs. Green nimitti is a member of the Chironomidae, one of the largest insect families, comprising approximately 10 000 species. (1) Chironomidae are informally known as chironomids or non-biting midges.

Chironomid midges are small (2 to 15mm) non-biting flies, characteristically seen swarming near water at dusk.

Chironomidae have a global distribution. Because of this, chironomids have been recognised as an important cause of environmental and occupational inhalation allergy; larvae and midges cause allergic reactions in approximately 20% of exposed people. (2)

Other members include Dicrotendipes fusconotatus, Procladius noctivagus and Conchapelopia cygnus. Chironomus thummi (see ImmunoCAP® i73) is found all over Europe, whereas Chironomus plumosus and Chironomus yoshimatsui are especially abundant in Japan.

More than 20 species of Chironomidae have been identified along a lakefront in central Florida, USA. Glyptotendipes paripes was the most abundant, followed by Chironomus crassi-caudatus. (3) Another report from southern California in the USA describes serious problems arising from man-made lakes, which have become habitats for various species of Chironomus midges. (4)

Green nimitti is a member of the Cladotanytarsus spp., which has a worldwide distribution; about 48 species of Cladotanytarsus have been described. (5) Green nimitti larvae occur in a wide variety of habitats, including lakes, rivers, thermal springs and brackish waters. Adult Cladotanytarsus form extensive nuisance swarms along the River Nile, and although green nimitti is distributed worldwide, the allergenic respiratory problems associated with this midge have mainly been reported in people living close to the Nile, in northern and central Sudan, and around Lake Victoria in Uganda. However, it has also been found in other parts of the world, near water reservoirs.

Allergen Description 

The major allergens appear to be chironomid haemoglobins. (6, 7, 8)

Two major allergens, with molecular weights of approximately 17 kDa and 32 kDa (sizes compatible with their being monomeric and dimeric haemoglobins) have been identified. (7, 9) A 66 kDa allergen has also been identified. (10)

Potential Cross-Reactivity

It is known that polymorph haemoglobins of many chironomid species are cross-reactive. (1, 8) Using sera from clinically sensitised subjects, a strong immunological cross-reactivity between 14 chironomid species of different localities from different continents was found. (1) The cross-reactivity derived (predominantly, at least) from haemoglobin components with common antigenic determinants in the different species. (1) However, although cross-reactivity was demonstrated between chironomid species and purified C. thummi haemoglobin (C. bernensis; C. annularius; C. plumosus; C. tepperi; C. tentans; Einfeldia spp. and Glyptotendipes pallens), weaker cross-reactivity was demonstrated with species of the genera Camptochironomus, Einfeldia and Glypotendipes, and green nimitti (Cladotanytarsus lewisi), which is phylogenetically more distant, showed a very weak degree of immunological cross-reactivity. (1)

In contrast, a later study demonstrated cross-reactivity between green nimitti and blood worm (Chironomus thummi). The larvae of Chironomus thummi are used as pet fish food, and haemoglobins have previously been shown to be major allergens (see ImmunoCAP (®) i73). Similar to C. thummi, immature forms of green nimitti also contain allergenic material, as demonstrated by skin tests using larval, pupal and adult extracts. (8)

A study evaluating skin-prick test reactivity of green nimitti midge extract and extracts of seven sub-dominant species of Nilotic Chironomidae found a limited degree of cross-reactivity, with Paracladopelma graminicolor, C. pseudomancus, Nanocladius vitellinus, and Cryptochironomus neonilicola; and particularly with Dicrotendipes fusconotatus, Procladius noctivagus and Conchapelopia cygnus. (11)

A cross-reactive relationship has been demonstrated between chironomids (not specifically green nimitti) and D. pteronyssinus allergy, between chironomids and mosquito allergy, and between chironomids and cockroach allergy, suggesting that a relationship exists. (12, 13) This suggests that sensitised patients may have increased serum-specific IgE to chironomids without apparently being exposed to chironomids. (14)

Clinical Experience

a. IgE-mediated reactions

Hypersensitivity to green nimitti has been widespread for a long time, particularly in the Sudan. The symptoms are mainly bronchial asthma and rhinitis. (11, 15, 16, 17)

Hypersensitivity to green nimitti was identified as a major problem in the Sudan from about 1925, and was shown to be as a result of the increased breeding of a single chironomid species: green nimitti. This was attributed to the mass emergence of these midges from an upsurge of larvae, as a result of a large increase in algae and diatoms caused by the retention of plant nutrients resulting from interruption to the natural flow of the Nile by the construction of dams. In sensitised patients, the degree of serum-specific IgE was related to the severity of clinical symptoms. (9, 17, 18)

In an early study, 16 Sudanese with bronchial asthma associated with exposure to green nimitti were investigated. Positive skin-prick tests were demonstrated in all subjects to an extract of this midge, and the majority had markedly elevated concentrations of circulating IgE. (17)

Among green nimitti-allergic Sudanese patients, 46.2% were shown to have IgE antibodies directed to the haemoglobin antigen Chi t 1, of the related midge Chironomus thummi. (2)

Skin-prick tests with green nimitti midge extract were conducted on asthmatic subjects in several localities in the Sudan and Egypt. A number of asthmatic individuals giving a positive reaction were also tested with extracts of seven sub-dominant species of Nilotic Chironomidae. There appeared to be a limited degree of cross-reactivity with these species (see above). Green nimitti-sensitive subjects giving positive skin-tests to these other species were 10 of 20 for Dicrotendipes fusconotatus; 12 of 28 for Procladius noctivagus; and 12 of 29 for Conchapelopia cygnus. In contrast, only 5 of 31 reacted to Paracladopelma graminicolor; 5 of 24 to Cladotanytarsus pseudomancus; 3 of 32 to Nanocladius vitellinus; and 2 of 28 to Cryptochironomus neonilicola. The results indicate that green nimitti is a major source of chironomid allergen(s) in these asthmatic subjects, and the authors suggested that hypersensitivity to green nimitti was probably far more widespread than was originally envisaged. (11)

b. Other reactions

Nil reported.

Compiled by Dr Harris Steinman, harris@allergyadvisor.com

References

  1. Baur X, Dewair M, Haegele K, Prelicz H, Scholl A, Tichy H. Common antigenic determinants of haemoglobin as basis of immunological cross-reactivity between chironomid species (Diptera, Chironomidae): studies with human and animal sera. Clin Exp Immunol 1983;54(2):599-607.
  2. Baur X. Chironomid midge allergy. Arerugi 1992;41(2 Pt 1):81-5.
  3. Ali A, Lobinske RJ, Chaudhuri PK. Long-term (1980-94) population trends of pestiferous Chironomidae (Diptera) along a lakefront in central Florida. J Am Mosq Control Assoc 1996;12(1):106-11.
  4. Lothrop BB, Mulla MS. Mode of existence and seasonality of midge larvae (Diptera: Chironomidae) in man-made lakes in the Coachella Valley, southern California. J Am Mosq Control Assoc 1995;11(1):77-85.
  5. Ghonaim M, Ali A, Amer M. Cladotanytarsus (Diptera: Chironomidae) from Egypt with description of a new species. Oriental Insects 2005;39:323-9.
  6. Tee RD, Cranston PS, Kay AB. Further characterisation of allergens associated with hypersensitivity to the "green nimitti" midge (Cladotanytarsus lewisi, Diptera: Chironomidae) Allergy 1987;42(1):12-9.
  7. Liebers V, Baur X. Chironomidae haemoglobin Chi t I--characterization of an important inhalant allergen. Clin Exp Allergy 1994;24(2):100-8.
  8. Tee RD, Cranston PS, Dewair M, Prelicz H, Baur X, Kay AB. Evidence for haemoglobins as common allergenic determinants in IgE-mediated hypersensitivity to chironomids (non-biting midges). Clin Allergy 1985;15(4):335-43.
  9. Gad El Rab MO, Thatcher DR, Kay AB. Widespread IgE-mediated hypersensitivity in the Sudan to the 'green nimitti' midge, Cladotanytarsus lewisi (Diptera: Chironomidae) II. Identification of a major allergen. Clin Exp Immunol 1980;41(3):389-96.
  10. Tee RD, Cromwell O, Longbottom JL, Cranston PS, Kay AB. Partial characterization of allergens associated with hypersensitivity to the 'green nimitti' midge (Cladotanytarsus lewisi, Diptera: Chironomidae). Clin Allergy 1984;14(2):117-27.
  11. Cranston PS, Gad El Rab MO, Tee RD, Kay AB. Immediate-type skin reactivity to extracts of the 'green nimitti' midge, (Cladotanytarsus lewisi), and other chironomids in asthmatic subjects in the Sudan and Egypt. Ann Trop Med Parasitol 1983;77(5):527-33.
  12. Galindo PA, Feo F, Gómez E, Borja J, Melero R, Lombardero M, Barber D, García Rodríguez R. Hypersensitivity to chironomid larvae. J Investig Allergol Clin Immunol 1998;8(4):219-25.
  13. Pascual CY, Crespo JF, San Martin S, Ornia N, Ortega N, Caballero T, Muñoz-Pereira M, Martin-Esteban M. Cross-reactivity between IgE-binding proteins from Anisakis, German cockroach, and chironomids. Allergy 1997;52(5):514-20.
  14. Galindo PA, Lombardero M, Mur P, Feo F, Gomez E, Borja J, Garcia R, Barber D. Patterns of immunoglobulin E sensitization to chironomids in exposed and unexposed subjects. J Investig Allergol Clin Immunol 1999;9(2):117-22.
  15. Gad El Rab MO, Kay AB. Widespread immunoglobulin E-mediated hypersensitivity in the Sudan to the "green nimitti" midge, Cladotanytarsus lewisi (diptera: Chironomidae). J Allergy Clin Immunol 1980;66(3):190-7.
  16. Kay AB, MacLean CM, Wilkinson AH, Gad El Rab MO. The prevalence of asthma and rhinitis in a Sudanese community seasonally exposed to a potent airborne allergen (the "green nimitti" midge, Cladotanytarsus lewisi). J Allergy Clin Immunol 1983;71(3):345-52.
  17. Kay AB, Gad El Rab MO, Stewart J, Erwa HH. Widespread IgE-mediated hypersensitivity in Northern Sudan to the chironomid Cladotanytarsus lewisi ('green nimitti'). Clin Exp Immunol 1978;34(1):106-10.
  18. Cranston PS, Gad El Rab MO, Kay AB. Chironomid midges as a cause of allergy in the Sudan. Trans R Soc Trop Med Hyg 1981;75(1):1-4.

As in all diagnostic testing, the diagnosis is made by the physican based on both test results and the patient history.