i75 European hornet

The European hornet (Vespa crabro) is a large vespid wasp native to most of Europe and Asia. It injects venom for self-defense and to capture prey via a stinging apparatus. In Europe, V. crabro is responsible for only occasional vespid venom allergic reactions, but these reactions are likely to be severe and can induce fatal anaphylaxis. Three allergenic molecules have been characterized in V. crabro venom to date, which cross-react to some degree with homologous proteins in venom from other Hymenoptera insects such as yellow jacket (Vespula spp.) and honeybee (Apis mellifera). 

Living environment

V. crabro is considered the largest native vespid wasp in Europe (6), with a body size of approximately 9‒10 mm in length and builds colony nests in the ground or sheltered areas (7). In the northern hemisphere, Hymenoptera stinging events generally occur during late summer or early fall, with peak events occurring in August (8). 

Worldwide distribution 

The European hornet is native to most of Europe and Asia and can also be found in eastern North America (9). 

Main

Female Hymenoptera insects have a stinging apparatus at the tail end of their abdominal segment, which is used for self-defense, to repel colony intruders, and to capture prey (5, 6, 10). A sting can deliver between 100 ng and 50 µg of venom (5). V. crabro is not particularly aggressive to humans, and usually only stings when provoked or disturbed.

Hymenoptera stings account for 9‒23% of all systemic allergic reactions, and 20‒40% of all types of  reported each year, making them a major cause of hypersensitivity responses (4). An estimated 50% of subjects who experienced fatal reactions had no documented history of a systemic reaction to Hymenoptera sting (11).

In Europe, V. crabro is responsible for only occasional vespid venom allergic reactions, but these reactions are likely to be severe (12). A case history analysis of 157 Hymenoptera allergic patients in Portugal estimated that the relative risk of a life-threatening reaction was approximately three times higher with V. crabro versus yellow jacket or honeybee (RR=2.74, CI 95%: 1.93‒3.89; R<0.0001) [ANT03]. In this study, the percentage of life-threatening reactions was 81.2% in the V. crabro allergic patients group (n=35), versus 27.8% in the Vespula spp. allergic group (n=97) and 24% in the Apis mellifera allergic group (n=25) (13).

In general, exposure to venom leads to a type I hypersensitivity reaction, with clinical symptoms that can include local burning, persistent local pain, angioedema, generalized urticaria, decreased blood pressure, bronchospasm, cardiac arrest, and respiratory and anaphylactic shock in sensitized individuals (14, 15). Interestingly, in a study of 220 patients allergic to bee, wasp, or European hornet venom, total IgE levels of patients with mild symptoms (e.g. grade I, generalized skin symptoms) were higher than those of patients with either moderate reactions (e.g. grade II, moderate pulmonary, cardiovascular, or gastrointestinal symptoms) or severe reactions (e.g. grade III, bronchoconstriction, emesis, anaphylactic shock, or loss of consciousness) (248.0 kU/l vs 75.2 kU/l vs 56.5 kU/l, respectively; p<0.001) [STU07].

A recent review paper identified 55 detailed cases of Vespa spp. hornet sting in 27 papers, with a mortality rate of 36.4% due mainly to multi-organ failure with common complications of renal failure and liver dysfunction (10).

In a report from Nepal, three subjects developed acute renal failure following multiple hornet stings (species unidentified) and were admitted to hospital; two patients recovered following hemodialysis and treatment and one patient died (8). A case report from Turkey described a 30-year-old male with no history of cardiovascular or systemic abnormalities who developed atrial fibrillation, shortness of breath, dizziness, and headache following a suspected V. crabro sting and recovered fully after emergency treatment with anti-coagulants and intravenous propafenone (16). A further case report from Serbia described a healthy 45-year-old male with no history of ischemic heart disease who developed acute myocardial infarction and anaphylaxis following a V. crabro sting and was admitted to ICU (5). Skin prick tests (SPT) did not confirm sensitivity to bee, wasp, or hornet and total serum IgE levels were normal (5). The patient was treated with coronary vasodilators, antiarrhythmics, anti-aggregation drugs, and sedatives, and discharged from hospital 20 days following the sting event (5).

Allergen immunotherapy

Immunotherapies for wasp venom aim to increase suppressor cytokines such as IL-10 and TNF-β, and decrease IL-4 secretion (4).

Author: RubyDuke Communications

Reviewer: Dr. Christian  Fischer 

Last reviewed:April 2022