The family of Tabanidae are 5-30 mm long insects with two wings and antenna. The cleg is one of the tiniest member of the family, 8-12 mm long and the flies have a grey-black appearance (Figure 2). Other genus of the Tabanidae family are Chrysops and Tabanus spp (Table 2. See also http://www.roberth.u-net.com/horseflies.htm).
Only female insects sting or bite. Haematopota species are able to approach their victim without noise, undetected and to settle upon exposed parts of the body without being felt, until the proboscis pierces the skin. A faint hum can usually be detected from Chrysops females as they draw close to their favourite point of attack i.e. the back of the head or neck. They settle on clothing and stealthily make their way to a place where they may sting. The clegs usually attack during late afternoon and they are very active in rainy weather of thunderstorm (the Dutch call them “regendaas” i.e. “rainfly”). Their habitat is in humid places like lakes and swamps.
Figure 2.
Table 2. Taxonomic distribution of the biting insects (in the Genus box the common used names are given for the Netherlands (NL), United Kingdom (UK) and Germany (GE)
After bites of flies, clegs and mosquitos usually there appears a local reaction with itch, redness and swelling. In literature rare cases are found with severe systemic reactions after these bites, as occurring more often after stings from Hymenoptera spp [1-5]. Insect allergen extracts for diagnostic work-up are not commercially available. Some investigators succeed in diagnosing the IgE mediated reaction by using homemade allergen extracts [1,3,5]. Also in this case, the UniCAP used concerned another genus of the Diptera (Tabanus), apparently not cross-reactive with the genus Haematopota. By using homemade extracts of clegs collected in the neighbourhood of the patient, we were able to detect the IgE antibodies responsible for the anaphylaxis.
As treatment we considered immunotherapy with whole body extract or purified extract from the salivary glands of the insects [2-4]. However, due to the low number of patients, we will not find an allergen extract manufacturer eager to produce this kind of treatment [6].
References
1. Freye HB, Litwin C. Coexistent anaphylaxis to Diptera and Hymenoptera. Ann Allergy Asthma
Immunol 1996;76:270-2.
2. Hrabak TM, Dice JP. Use of immunotherapy in the management of presumed anaphylaxis to the
deer fly. Ann Allergy Asthma Immunol 2003;90:351-4.
3. McCormack DR, Salata KF, Hershey JN, Carpenter GB, Engler RJ. Mosquito bite anaphylaxis:
immunotherapy with whole body extracts. Ann Allergy Asthma Immunol 1995;74:39-44.
4. Hemmer W, Focke M, Vieluf D, Berg-Drewniok B, Gotz M, Jarisch R. Anaphylaxis induced by
horsefly bites: Identification of a 69 kD IgE-binding salivary gland protein from Chrysops spp (Diptera
Tabanidae) by werstern blot analysis. J Allergy Clin Immunol 1998;101:134-6.
5. De Maat-Bleeker F, van Bronswijk EMH. Allergic reactions caused by bites from blood-sucking
insects of the Tabanidae family, species Haematopota pluvialis [abstract]. Allergy 1995;50(suppl
26):388.
6. De Jong NW, Vermeulen AM, De Groot H. Allergy to bumble bee venom. III. Immunotherapy followup
study (safety and efficacy) in patients with occupational bumble-bee anaphylaxis. Allergy
1999;54:980-4.
Allergy Field concerned & Key words: anaphylaxis, insects, RAST, immunotherapy
Summary
We describe a rare case of anaphylaxis after bites of a cleg, endemic for the southeast of the
Netherlands. It concerns a 6-year old boy with several occasions of anaphylactic reactions, the
responsible insect identified as Haematopota pluvialis. These insects are biting insects of the order
Diptera, family Tabanidae (“horseflies”) The IgE-mediated reaction was confirmed using sepharosecoupled
whole body extract of captured insects. As there is no commercially available extract for
immunotherapy, the only treatment consisted of avoidance and first aid medication (an Epipen® auto
injector) in case of accidental bites.
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