Summary

Common related species: C. yoshimatsui; C. plumosus; C. salinarius; C. kiiensis - dominant chironomid species in Korea

Insect

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

Allergen

Allergen Description

The body fluid of chironomid midges contains haemoglobin molecules, known as erythrocurorins, that have a high degree of polymorphism. In C. thummi thummi, 11 forms occur, with the primary structure of the various erythrocurorins differing by 16 to 48% of the amino acid residues. These haemoglobins are potent allergens that can sensitise and induce allergic disease. Besides the haemoglobin allergens, a range of proteins have been implicated in sensitisation, including those with a molecular weight of 55, 31, 27, 26, 24, and 23 kDa.

The following allergens have been characterised to date:

*Recently, based on the analyses of a study, the IUIS Allergen Nomenclature Sub-Committee renamed Chi t 5, 6, 7 and 8 isoallergens of Chi t 3, even though their sequence identities to Chi t 3 were below the 67% threshold previously defined for isoallergens. The remaining haemoglobins, previously designated Chi t 1, 2, 4 and 9, retained their previous names.

The presence of a tropomyosin has also been inferred.

The presence of a glutathione S-transferase enzyme has been suggested.

Although Chi t 1 is the most prominent allergen of C. thummi, its levels probably vary according to the development stage of this organism. An evaluation of the equivalent allergen in the closely-related chironomids C. yoshimatsui and Tokunagayusurika akamusi found that extracts of C. yoshimatsui larvae and pupae did not inhibit specific IgE antibody to adult C. yoshimatsui. Mature adult C. yoshimatsui extract had about 10 times more inhibitory substance than the young adult. Haemoglobin was degraded during metamorphosis. The inhibitory substance against the specific-IgE antibody to adult T. akamusi was highest in the female body, less in the egg, and even less in the wing, leg and male body.

In a German study of 188 subjects who were exposed to the larvae of C. thummi, 61 individuals were found to be sensitised to Chi t 1, of whom 24 were monosensitised to this allergen and to no other aeroallergens tested.

Sera of 229 Japanese, 17 Taiwanese, and 92 Swedish patients were tested for antibodies against Chi t 1 and against crude extracts from the Japanese midges Tokunagayusurika akamusi and Cricotopus sylvestris. Twenty-seven (29.3%) Swedish and 113 (45.9%) Japanese subjects showed IgE reactivity with at least one of the tested chironomid allergens, mainly Cr. sylvestris. Of the Japanese serum samples, only 4.1% contained specific IgE against Chi t 1. No Taiwanese subjects were positive for Chi t 1. Of the Swedish patients, 10.9% had antibodies to Chi t 1, compared with 5.4% for T. akamusi. Nearly all tested Japanese serum samples showed cross-reactivity between Chi t 1 and Cr. Sylvestris.

A tropomyosin has been isolated from the closely-related species C. kiiensis, a dominant species of non-biting midges in Korea. Skin tests using extracts from C. kiiensis adults were performed on 275 allergic patients, of which 14.2% were positive. Specific IgE to the equivalent recombinant tropomyosin was detected in 17 (81%) of 21 patients whose skin-test results were positive.

Importantly, chironomid allergen was shown to be present in the air, varying from 6.8 to less than 0.3 ng/. In Toyama, Japan, seasonal fluctuations of airborne chironomid allergen demonstrated large peaks in summer (June to August), with a tendency to decrease in winter. Significant correlation was shown between airborne chironomid allergen and the dry weight of chironomid midges in a period before air sampling. However, the weather (temperature, wind speed and precipitation) did not appear to play a role.

Route Of Exposure

Allergen Exposure

Chironomidae (chironomids, also known as non-biting midges) are one of the most ubiquitous, diverse, and ecologically important groups of aquatic macro-invertebrates, the most widespread insects in fresh water, and occur on all continents including Antarctica.

Globally, there are an estimated 20 000 species of chironomids, with 4 000 species presently known. Of these, nearly 100 species in the subfamilies Orthocladiinae, Tanypodinae, and Chironominae have been reported to emerge in large numbers and pose pest problems. Chironomids include a number of species, e.g. Chironomus, Spaniotoma, Metiocnemus, Rheotanytarsus and Tokunagayusurika. Chironomus contains a number of members, e.g. C. thummi, C. plumosus (lake fly), C. yoshimatsui (common in Japan), etc. In recent years, adult Chironomidae (particularly Chironomus yoshimatsui and Tokunagayusurika akamushi), emerging from polluted natural and man-made aquatic habitats in urban areas of Japan, have become a severe nuisance resulting in economic problems.

The genus Chironomus, to which the blood worm (Chironomus thummi) belongs, includes the delicate, primitive, gnat-like flies that inhabit wetlands and spend their larval stage in ponds and slow streams.

Chinonomidae are midges 1 to 10 mm long and resemble mosquitos, but their mouthparts are elongated or may be absent. Adults are grey to black and the thorax usually has a midline furrow. The larvae of most species are aquatic and live in tubes or cases composed of fine particles of the substrate. Larvae are important food for other aquatic organisms. Larvae of many Chironomus species are red because of haemoglobin in their blood, and hence are known as blood worms. Eggs are laid in water, though the terrestrial species oviposit on wet soil or other surfaces. Adults live for 2 to 3 days. Large mating swarms may be formed by the males 1 to 10 metres above ground in the evening when there is little wind. Females usually do not swarm, but rest on marginal shore vegetation and structures until they fly into a swarm of males, select a male, and copulate. Midges are attracted to lights at night and may cause problems in residential areas. Conspicuous swarms may also hover over bushes and trees, and may enter houses in the evenings.

The adult members have many-segmented antennae, often longer than the head and thorax. Their bodies are soft and they are easily confused with the mosquito; they may be known as non-biting mosquitoes. Adults are known by a variety of inconsistent common names, which may result in confusion or misidentification. For example, chironomids are known as ‘lake flies’ in parts of Canada, as ‘sand flies’, ‘muckleheads’, or ‘muffleheads’ in various regions of the USA Great Lakes area, and as ‘blind mosquitoes’ in Florida. However, they are not mosquitoes at all, and the term ‘sand flies’ generally refers to biting flies unrelated to the Chironomidae.

In western countries, mainly the species C. thummi (also identified as C. riparius) is described; whereas in Japan, closely related species such as (for example) C. plumosus, C. yoshimatsui and Tokunaga akamusi are more predominant. The characterisation and identification of midges is extremely difficult, which may result in some confusion.

Importantly, both the larvae and the adult midges have been implicated in disease.

As they develop into adults their bodies fragment, and the particles which fall can result in conjunctivitis, rhinitis and asthma by inhalation in settlements near lakes or rivers. Dead bodies accumulate on the ground around homes and lights, break up, and can be inhaled.

Clinical Relevance

a. IgE-mediated reactions

Asthma and rhinitis caused by hypersensitivity to Chironomidae (non-biting midges) has been a problem in the Sudan since about 1927 and appears to be due to a single chironomid species, Cladotanytarsus lewisi. Since then, research has implicated a range of other Chironomidae, and in particular C. thummi, as prominent causes of sensitisation in individuals exposed to this insect. Both larvae and the adult form (midges) are implicated. In countries such as Sudan, the United States, Egypt and Japan they are the cause of serious environmental allergy, and in particular in settlements near lakes, such as in Sudan, Venice and certain regions of Japan. Authors have therefore argued that chironomids should be seen as significant environmental and occupational allergens.

In Europe, and particularly in Spain, allergy to chironomids is infrequent, and has only been described in patients who handle the red chironomid larvae used as fish food. These may cause allergic sensitisation in fancy fish enthusiasts using blood worms as aquarium food, researchers, and fish food workers. Reactions may also result from exposure to dust of lyophilised larvae. They are commercially known as red grubs or blood worms, and are usually kept deep-frozen or freeze-dried. Blood worms (red grubs) need to be differentiated from mealworm (golden grubs, or yellow mealworm) which are also used as fish food but are larvae from Tenebrio molitor. Segmented worms of the genera Polycirrus and Enoplobranchus have bright red bodies and are also usually used for bait.

Considering the close relationship and proven cross-reactivity between (non-biting) midges, particularly those belonging to the Chironomus genus, sensitisation may be more prevalent than presently considered.

Although fishermen, fish hobbyists, pet shop owners, and individuals keeping aquariums (aquarists) are considered to be those mainly exposed to C. thummi and other chironomid larvae used as fish food or bait, adult midges may be overlooked as one of the most important allergens in asthma and rhinitis. The main allergen, a haemoglobin, persists in both live and dead non-biting midges; thus, sensitised individuals need to avoid dead midges as well. This is particularly relevant for individuals living in the vicinity of standing waters and wetlands, for these insects are commonly found there. Furthermore, chironomids may play a role in summer exacerbation of asthma in particular regions where mites are present. Hypersensitivity to larvae has been reported to cause urticaria, rhinoconjunctivitis, asthma, angioedema, and even anaphylaxis.

In light of the high degree of cross-reactivity between C. thummi and other closely-related chironomid species, it is relevant to highlight other studies in addition to those directly related to C. thummi.

A number of case reports illustrate the range of possible clinical effects following contact with chironomids.

One report describes a 48-year-old woman living by a river, diagnosed with asthma caused by chironomid midges and positive in RAST tests. Similarly, 3 patients with rhinoconjunctivitis and/or asthma as a result of contact with midges and living near lakes in Wisconsin, USA, were all positive in RAST. Another report describes a 43-year-old male researcher who developed allergic rhinitis while researching midges in the surrounds of eutrophic Japanese lakes. His serum-specific IgE confirmed sensitisation.

Individuals may become sensitised and affected by chironomid larvae, as reported in 5 German asthmatic fish hobbyists, all positive in RAST tests. Although reports describe primarily the immediate onset of symptoms, a delayed allergy reaction was described in a 47-year-old fish hobbyist who developed erythema. Specific IgE was positive, and so was patch and scratch testing with extract from dried fish food containing chironomids. The authors surmised that the facial localisation of the eczema was probably due to airborne contact dermatitis, and they ventured that flying chironomid midges may also cause airborne contact dermatitis.

A 33-year-old woman described how, immediately after feeding her fish with a well-known brand of Chironomus larvae, she experienced bouts of sneezing, itching in the nose and eyes, rhinorrhoea, and tearing of the eyes, followed a few minutes later by ocular angioedema and dizziness. This clinical picture persisted, with difficulty in breathing, wheezing, and dry cough.

Similarly, hypersensitivity to midge larvae was described in a 23-year-old patient who on two occasions, after being in contact with fish-food, experienced rash, rhinoconjunctivitis, dyspnoea and dysphagia. Skin-prick tests and specific IgE, as well as conjunctival provocation, confirmed the IgE-mediated mechanism.

An account of a series of chironomid-allergic patients included a report of a 34-year-old woman who experienced six attacks of severe periorbital oedema and conjunctivitis, mainly on the right-hand side, which persisted for up to a week. Not freely volunteered was that she fed tropical frogs and fish. Skin-prick tests with dried, radiated or frozen ‘blood worms’ (the larvae of the Roja Mosquito, C. plumosus) were all positive, with huge wheals averaging 30 mm in size, and delayed reactions lasting for 2 days. Serum-specific IgE was significantly raised for C. plumosus, and negative for green Nimitti midge (Cladotanytarsus lewisi). She handled the larvae with her right hand, which explained why the right eye was most affected. The young man who had sold the fish foods described itching of his hands for about 30 min after handling them, and also had a very extensive immediate and delayed skin-test reaction. Subsequently, a 33-year-old man presented with a history of severe conjunctivitis preventing him from driving for weeks, occasional swelling of lips, allergic rhinitis, and occasional severe asthma. He had kept tropical fish for many years. Prick-to-prick tests with retained samples from the first patient resulted in immediate and delayed reactions.

Four patients with occupational allergy to Chironomus larvae (group 1) were compared with seven individuals, also sensitised to Chironomus larvae but who had apparently not been exposed to them (group 2). All patients showed elevated specific IgE against C. thummi, and positive skin-prick tests and provocation tests with Chironomus larvae. The red midge larvae wheal size was significantly larger in group 1 than in group 2. Significant differences in levels of C. thummi serum-specific IgE were also demonstrated between group 1 (52.12 kU/l) and group 2 (1.5 kU/l). The patients in group 2 had high levels of specific IgE against other allergens (D. pteronyssinus, shrimp and/or common mosquito), and had positive SPTs to these allergens, while the patients in group 1 were only sensitised to chironomids. The authors suggested that the patients in group 2 were sensitised to Chironomus as a result of cross-reactivity with other insect or crustacean species.

A 24-year-old male, who had experienced urticaria-angioedema after ingestion of Crustacea, reported recurrent episodes of angioedema of the eyelids and lips when feeding fish in an aquarium using a lyophilised product of C. thummi larvae. The areas of the distorted swellings were slightly erythematous and very itchy, reaching a peak within a few minutes and then disappearing after a couple of hours. The patient also reported that he had once developed acute asphyxia, probably as a result of oedema of the tongue and laryngeal or pharyngeal oedema. Skin-prick test with C. thummi extract was positive, and C. thummi serum-specific IgE was raised (25.5 kU/L).

Similarly, 7 cases of asthma and allergic rhinitis induced by non-occupational contact with pet-fish food were reported, with sensitisation to Chironomus demonstrated in most of the patients. Daphnia is also known to be a specific allergen.

Adverse reactions may not necessarily occur from skin contact with the larvae but from inhalation of the larvae allergens, as described in a patient who showed severe reactions to skin testing with Chironomidae.

Asthma induced by chironomid midges was described in a 48-year-old woman. Chironomid midges occurred in the river beside her house. Serum-specific IgE was raised for C. thummi and C. plumosus. Skin-prick testing with the latter provoked a mild acute asthma attack. The midges found swarming around her house were identified as C. nippodorsalis.

Even young children may be sensitised, as illustrated by the report of a 10-year-old child with increasing symptoms of skin and respiratory allergy related to contact with swarms of C. salinarius during summer. Both a prick test with a suspension of the entire body of the C. salinarius and the RAST were strongly positive.

Unusual adverse reactions have been described. IgE-dependent nephrotic syndrome due to inhalation of chironomid larvae was reported to have occurred in a 54-year-old man, who ground lyophilised C. thummi larvae to feed exotic fish. At the time of preparation 5 months earlier, he had experienced mild rhinitis. His present symptoms included extensive facial angioedema and dyspnoea, which subsided within a few hours without any treatment. Within 2 days, generalised oedema and weight gain occurred. Subsequently, proteinuria was detected, and nephrotic syndrome was diagnosed. A skin-prick test with powder made of larvae resulted in “an impressive reaction”.

Protein contact dermatitis from C. thummi has been reported. A study using patch tests disclosed a delayed-type hypersensitivity to 4 different species of chironomids (larvae of C. thummi, C. plumosus, and 2 different species of Glyptotendipes) as the probable cause of airborne facial contact dermatitis. In addition, asymptomatic immediate-type allergy to chironomids was demonstrated by scratch tests and specific IgE.

Patients have been reported who developed urticaria and/or angioedema after contact with C. thummi or closely-related species used as fish food.

The prevalence of sensitisation to chironomid larvae may be significant.

In Japan, chironomid midges, in particular C. yoshimatsui, are considered one of the most important allergens in asthma. In one study nearly 40% of the patients with asthma had high titers of specific IgE to chironomid. Similar findings are reported in other studies. Of patients with asthma living by an eutrophicated lake (waters rich in mineral and organic nutrients), 12-21% were positive in serum IgE testing to different chironomid species. Similarly, in an eutrophicated lake-side community near Oxford in the UK, where chironomid midges were investigated as one cause of asthma, around 8% of the entire community had developed IgE antibodies. Although the incidence of allergic reactions in this community was low, specific IgE correlated significantly with relevant symptoms.

Out of 51 Japanese house dust mite-asthmatic patients, 49% were positive to C. yoshimasui. In Korea, 20% of 475 patients with respiratory allergy were positive when skin-tested with chironomids. The authors suggested that chironomids should be considered important respiratory allergens.

An early German study suggested that Chironomidae larvae and midges cause allergic reactions in approximately 20% of exposed people; those affected are predominantly aquarists using insect larvae as fish food, and environmentally exposed subjects living in areas abounding in water. The supportive studies included 642 subjects of whom 205 were aquarists, 85 exposed occupationally, and 352 environmentally exposed. Of the total group, 123 were shown to be sensitised to chironomids. Using highly purified allergens, it was demonstrated that Chironomidae haemoglobins (Chi t I) represent the major allergenic components causing rhinitis, conjunctivitis and bronchial asthma. The authors considered that considerable immunological cross-reactivity exists between haemoglobins of the same and closely-related Chironomidae species, but that genetic factors also seemed to be important.

Similarly, a German publication reported that one-third of 99 subjects involved in the manufacture or feeding of fish with food prepared from Chironomus larvae were clinically affected with symptoms of respiratory allergy, and sensitised to haemoglobin allergens of the larvae.

In a Spanish study of 465 patients with rhinitis and/or asthma who were skin-tested, 19 showed a positive skin-prick test with chironomids, comprising 4.1% of all patients and 6% of the atopic patients. None were monosensitised. Significant correlations were found between skin-prick test results with chironomids and with mites. Of the 19 patients, 15 had a positive skin-prick test with the common mosquito (C. pipiens). Seven patients showed elevated IgE to D. pteronyssinus, 6 had elevated shrimp serum-specific IgE, and 10 elevated A. communis serum-specific IgE. Provocation tests with chironomids were positive in 14 patients (four nasal and 10 conjunctival tests). Conjunctival provocation tests in 16 controls were positive in three; all three showed positive skin-prick tests with chironomids. One patient (an aquarist) had occupational allergy from the larvae. Five patients showed immediate wheal reactions and one patient suffered an anaphylactic reaction after several mosquito bites. Only two patients remembered having been in contact with chironomids as fish food. The authors suggested that for a variety of mechanisms, hypersensitivity to these larvae may occur without apparent contact with them. These including: 1) inhaling particles of chironomids or others that are cross-reactive with them; 2) exposure to products that are used as fish food and contain chironomids; and 3) through cross-reactivity with other allergens such as mites, shrimp or mosquitoes.

In a German study of 642 persons with hobby-related (n = 205), occupational (n = 85), or environmental (n = 352) contact with the midge and larval allergen Chi t 1, occupationally sensitised subjects who had been heavily exposed showed higher levels of antibodies, were more frequently diagnosed as having asthma and less frequently as having conjunctivitis, and had a significantly shorter latency period when compared to environmentally exposed people or aquarists. In a subsequent report, the authors described a German study of 225 aquarists and fish-food factory workers who had been exposed to C. thummi, of whom 34% were shown to have specific IgE to chironomids and had closely associated symptoms. Conjunctivitis (63%) and rhinitis (62%) were predominant, followed by asthma (45%) and urticaria (37%). Individuals with asthma were shown to have the highest serum-specific IgE levels, and symptoms were associated with degree of exposure. While nearly all IgE-sensitised subjects of the medium-, high-, and very high-exposure group were symptomatic, only 57% of the sensitised individuals of the low-exposure group reported complaints.

A German study evaluated the skin-test reactivity and serum IgE of 43 individuals with respiratory, conjunctival, or cutaneous reactions when in contact with dust containing larval chironomid components. Twenty-nine of the 36 symptomatic subjects were skin-test positive to crude extracts of mixed chironomid larvae, C. thummi midges, and in most cases with C. thummi haemoglobin components. The extracts comprised larvae and adults of C. thummi, C. annularius, C. tentans, C. tepperi, and from a commercially available fish food containing lyophilised larvae of different species. Thirty-three of the 43 symptomatic subjects were shown to have elevated serum-specific IgE to crude extracts of mixed larvae, C. thummi midges, and the various C. thummi haemoglobin components. Sera of five sensitised persons had IgE antibody directed at proteins in extracts of the various Chironomus species and Cladotanytarus lewisi, which suggested some cross-reactivity between species.

Studies of closely related species are appropriate.

In an Egyptian study, skin-prick tests with crude extract of C. calipterus were positive in 20 out of 25 children with respiratory allergy. Chironomid-specific IgE-ELISA was demonstrated in the sera of 17 (85%) of the chironomid skin-positive patients. These 17 patients were negative on skin-prick test to house dust mite. The authors concluded that sensitisation to chironomid allergens should be considered in respiratory allergy caused by arthropods.

Japan in particular is known for a high prevalence of sensitisation to chironomid midges, in particular C. yoshimatsui and C. plumosus. A study evaluated serum-specific IgE to chironomid midges in asthmatic patients around the Lake Suwa area, and compared these with those of the Matsumoto area (control area). Of 123 Japanese adult patients with asthma, 33 (50.8%) were positive to mite, 28 (43.1%) to silkworm, 11 (16.9%) to C. yoshimatsui, 8 (12.3%) to C. plumosus, and 3 (4.6%) to the chironomid Tokunagayusurika akamusi. In the Lake Suwa area, C. plumosus and T. akamusi showed a lower number of positive reactions, and appeared to be related to the advanced age of patients in this area. The authors suggested that chironomids (together with mite and silkworm) are an important cause of asthma in the Lake Suwa area, but affected old asthmatic patients less than asthmatic children. An earlier Japanese study reported that 27.5% of 80 nasal-allergic medical students showed positive reactions to chironomid allergen; 9 (11.3%) had positive reactions to caddis fly allergen and 18 (22.5%) to silkworm moth allergen. Therefore these insects are relatively more common than expected, and are important allergens in nasal allergy.

Of note, 38% of 303 asthmatic patients in metropolitan Tokyo were prick-test positive to either larval or adult Tokunagayusurika akamusi midges. Skin- and serum-specific IgE tests to extracts of T. akamusi larvae and adult midges were conducted in randomly selected asthmatic patients. The frequency of sensitisation to these aeroallergens was only surpassed by sensitisation to mites.

In another Japanese study clarifying the role of insects as allergens in allergic rhinitis, specific IgE to moths, midges, and cockroaches (together with 10 other allergens) was measured, using sera from 560 allergic-rhinitis patients who visited 20 otolaryngological clinics nationwide. Frequencies of sIgE positive to moth, midge, and cockroach were 32.5%, 16.1%, and 13.4% respectively. The prevalence of patients with positive nasal challenge increased depending on the RAST class to the insects. Other Japanese studies also indicate frequent sensitisation to chironomids, in particular adult C. yoshimatsui in 19.4% and C. thummi in approximately 3%.

Intradermal tests with C. plumosus extract were undertaken on 718 asthmatic children aged from 6 to 15 years in 10 areas of Japan, of whom 200 (27.9%) were positive. The positive rate increased in proportion to age. Positive rates ranged from 12.6% in Akita to 45.5% in Okinawa. The C. plumosus-positive asthmatics had significantly more attacks than the C. plumosus-negative ones in the summer. The positive rate of asthmatics living near paddy or farm fields was significantly higher than that of those in urban residential areas (31.3% vs 23.8%). These results indicate that chironomid midge is one of the most common and important allergens in Japan.

A study of 119 asthmatic children living in Toyama, Japan, investigated by prick tests for hypersensitivity to chironomid antigens, reported that the prevalence of positive prick tests to the antigens of adults of Polypedilum kyotoense, Chironomus yoshimatsui and Tokunagayusurika akamusi and the antigens of the larvae of Tokunagayusurika akamusi and Dermatophagoides farinae were 23.5%, 17.6%, 7.6%, 16.0% and 94.2% respectively. The correlation of the wheal size, the threshold dilution in the intradermal test, the RAST score, and the result of the provocation test were all significant.

Specific IgE for two additional midge species was measured in 27 asthmatics who had been positive to any of the 3 adult midge antigens tested, and was raised in 59.3% for C. plumosus and in 100% for Tanytarusus oyamai. P. kyotoense allergens were not cross-reactive with D. farinae. These results suggest that the extracts of chironomid midges have strong allergenicity, and are one of the important inhalant antigens causing asthma in Toyama.

Similarly, in a Swedish study of 2 368 consecutive instances of adults with asthma and/or rhinitis the incidence of positive skin-prick test with a chironomid was 14% (26% in atopics and 4% in non-atopics). RAST with chironomid was positive in 4% of 110 consecutive sera (8% in atopic sera).

b. Other reactions

Nil documented.

Cross-Reactivity

Cross-reactivity between chironomid species has been reported extensively. In addition, cross-reactivity to other allergens, such as common mosquitoes, moths, house dust mite, shrimp, anisakis and cockroach, and green nimmity (the wide-spread cause of asthma and rhinitis in Sudan) has been reported.

Although cross-reactive allergens are present, in particular haemoglobin (a major cross-reactive allergen between chironomid species), other panallergens may also be present, as well as species-specific allergens. Furthermore, the allergenicity of chironomid midges changes during the metamorphosis from larva to adult, and is not common among all species. But this is not true for all the midge species, for although the cross-reactivity relationship may be high, it appears to be complex.

This is illustrated in an evaluation of immunological cross-reactivity between 14 chironomid species from different continents, using the haemoglobin fraction of C. thummi, that found that cross-reactivity was at least predominantly from haemoglobin components with common antigenic determinants in the different species, and that 6 extracts of adult midges were able to inhibit C. thummi haemoglobin in a similar manner to that employed by the crude larval extracts. Eight chironomid species showed a dose-dependent inhibition of IgE binding to purified C. thummi total haemoglobin (C. bernensis; C. annularius; C. plumosus; C. tepperi; C. tentans; Einfeldia sp. and Glyptotendipes pallens). The authors suggested that the inhibition results reflected the degree of evolutionary relationship of the different chironomid species with regard to C. thummi. Weaker cross-reactivity was obtained with species of the genera Camptochironomus, Einfeldia and Glypotendipes, whereas Cladotanytarsus lewisi, which is phylogenetically more distant, showed a very weak degree of immunological cross-reactivity.

In particular, a wide cross-reactivity exists between Chi t 1 and haemoglobins from a wide range of chironomid species, and in particular from 14 of the 15 chironomid species previously analysed. In a study utilising monoclonal antibodies raised against Chi t I-component III, two recognised an epitope which is expressed in nearly all closely-related species, but 3 monoclonal antibodies recognised epitopes which were expressed in only a few species of the same genus. Similarly, haemoglobin from C. thummi has been shown to have a 30 to 59% homology with that of the chironomid, Polypedium nubifer. Cross-reactivity has also been demonstrated to occur between Chi t 1 and the midge, Cricotopus sylvestris.

The panallergen, topomyosin may also play a role in potential cross-reactivity. Although not yet isolated from C. thummi, tropomyosin has been isolated from other closely-related Chironomus species, in particular C. kiiensis. This tropomyosin has a high homology with tropomyosins known to be allergens in various arthropods (Periplaneta americana, 86.3%; Panulirus stimpson, 78.9%; Dermatophagoides pteronyssinus, 76.5%).

Tropomyosin occurs in a wide range of arthropods, including shrimps and lobsters. Tropomyosins are also found in other invertebrates such as cockroaches, chironomids and mosquitoes. RAST inhibition studies have shown that cross-sensitivity exists between D. pteronyssinus and both cockroaches and chironomids.

A 14-year-old boy with seasonal rhinoconjunctivitis and an immediate local reaction to a mosquito bite was found to have raised serum IgE to a number or arthropod species, including C. thummi (3.2 kU/L), Aedes communis (12.7 kU/L), D. pteronyssinus (3.2 kU/L). He had no contact with chironomids and his symptoms were only seasonal. A common 25 kDa protein was demonstrated on immunoblot and postulated to be a glutathione S-transferase enzyme.