Occupational immediate‐type allergy to locusts in a zookeeper

Locusts belong to the arthropod phylum and the insect class [1]. The European migratory locust (Locusta migratoria; genus Locusta) is characterized by its ability to migrate – also in form of dreaded plagues – as well as its quick adaptability to various environmental conditions [2]. It has long been the subject of biogeographic and ethologic research due to its population-dependent phenotypic plasticity (known as phase polymorphism, marked by the development from an individual phase [solitary phase] into a swarm phase [gregarious phase]) [3]. Migratory locusts – along with cockroaches and mealworms – are also used as feed for carnivorous reptiles and are available at pet shops. There have been reports of immediate hypersensitivity reactions, primarily in laboratory employees, after exposure to Locusta migratoria and other insects [4, 5]. We report on a 41-year-old female zookeeper whose occupational duties included feeding reptiles. Upon contact with migratory locusts (used as feed) she experienced hoarseness, lip paresthesia as well as pruritus, erythema, and wheals on her hands. Moreover, rubbing her eyes led to conjunctival erythema. Over the course of one year, she developed a productive cough and respiratory problems, for which she was initially treated with antibiotics. The results of off-site pulmonary function tests – as well as an examination by an ENT specialist – were normal. The patient denied any symptoms on weekends and during vacations as well as when feeding crustaceans (for example, daphnia) and mosquito larvae to her own fish at home. Neither she nor her family had a history of atopic disease, nor was she taking any medication. A rub test with a dead migratory locust resulted in severe contact urticaria (40/80 mm) (Figure 1). A hospital employee acting as control did not show any positive reaction. Skin exposure to a live locust – without iatrogenic alteration of the epidermis – also led to contact urticaria in our patient. ELISA testing (ImmunoCAP® Phadia) showed specific IgE antibodies to migratory locusts (1.7 kU/l – CAP 2). Specific IgE antibodies to tropomyosin, cockroaches, moths, mosquitoes, red mosquito larvae, mealworms, daphnia, and TetraminTM (feed) were not detected. Total IgE was slightly elevated at 102 kU/l (normal range for adults: < 100 kU/l). Prick testing for aeroallergens (including house dust mites) was negative. Mast cell tryptase was within normal limits. Clinical Letter Based on her clinical symptoms along with the evidence of type 1 sensitization to migratory locusts (ELISA, rub test, skin exposure test), the patient was diagnosed with an allergy to migratory locusts. There was no evidence of any sensitization to or cross-reactivity with other arthropods. For symptom relief, she was advised to take cetirizine tablets. She was also given an emergency kit that included an antihistamine, a corticosteroid, and a beta-adrenergic agent. Based on a dermatologist’s report, an occupational disease assessment procedure was initiated. The patient was forced to quit her job, because she would not have been able to avoid allergen exposure at her workplace. In terms of occupational skin diseases, arthropods are relevant for both infectious (primarily as vectors or pathogen reservoirs) and allergic disorders. Among laboratory workers at a research center where locusts were bred, Burge and colleagues reported exposure-related cases of respiratory disorders (26 %), rhinitis (35 %), and urticaria (33 %) [6]. While the authors suggested a connection between atopy and the prevalence (or early onset) of occupational asthma, later studies have failed to confirm such an association [4, 7]. Apart from elevated total IgE, our patient did not show any signs of atopic diathesis. Nevertheless, it is safe to assume that continued exposure, especially to a large number of insect allergens, would have entailed an increased risk for additional sensitizations and respiratory problems in case of [8]. To our knowledge, this is the first reported case of locust allergy in a zookeeper. Occupational allergies to locusts have rarely been published and predominantly relate to research lab workers. In migratory locusts, the peritrophic membrane, an intestinal membrane excreted in feces, has been identified as the primary allergen source [7]. Other epitopes have been found in the wings [4]. Although cross-reactivity presumably exists between different insect allergens, there has been no clear