Asthma caused by a pet bat


I t is known that materials derived from non-Hymenoptera insect species can be potent respiratory allergens. Mealworms, larvae of the beetle Tenebrio molitor, are widely used as fishing bait. Allergic bronchial asthma to mealworms has already been described ( 1). Four of five bait handlers who were exposed to T. molitor in a warehouse suffered from IgE-mediated allergic asthma, rhinitis, or contact urticaria. Another report concerns a 26-year-old female animal handler. Her job included feeding the animals T. molitor beetles. For years, she had complained of severe work-related symptoms of rhinoconjunctivitis. Specific IgE to extracts from the larvae, pupae, and adult stages of T. molitor was demonstrated by RAST ( 2).

Respiratory allergy to inhaled bat feces is known in African and South American countries. In Sudan, for instance, many asthmatic patients attribute their symptoms to inhalation of bat droppings in their homes. The feces drop through cracks in the ceiling into the rooms below. This material can be inhaled, causing allergic respiratory disorders. Specific IgE antibodies have been shown to bat feces ( 3).

At our allergy unit, a 31-year-old patient who developed bronchial asthma after occupational exposure to bats (Chiroptera) has been described. Skin tests and RAST with bat allergens confirmed the presence of an IgE-mediated allergic reaction. Because the patient, as a dedicated scientist, could not abandon his contact with bats, specific immunotherapy with bat-allergen extracts was undertaken. After 1 year of therapy, the patient was free of symptoms while exposed to Chiroptera ( 4). Positive skin tests and IgE (RAST) to bat feces were also detected in atopic patients living in tall buildings and old houses in Buenos Aires, Argentina ( 5).

We present here a case of allergic asthma and rhinoconjunctivitis caused by IgE-mediated allergy to the yellow mealworm (T. molitor) and at the same time to bat feces. To our knowledge, this is the first report of this combination.

A 29-year-old female zoologist was referred to the allergy unit because of a history of respiratory symptoms for 10 years. In the morning, she complained of rhinitis, conjunctivitis, and coughing. Especially when she stayed at home during the day, asthmatic attacks occurred in the evening. For many years, she had worked with bats. Two years before, she had decided to keep a bat at home; afterward, her symptoms got worse. She fed the bat with mealworms, which are the larvae of theT. molitor beetle. Absence from home coincided with decreased severity of the symptoms.

Clinical examination revealed no wheeze on chest auscultation, spirometry was normal, and prick tests to common inhalant allergens, including trees and grass pollen, house-dust and storage mites, molds, and animal epithelia, as well as cow's milk and egg white, were negative. The bronchial methacholine provocation test showed unremarkable bronchial hyperreactivity. A scratch test with the patient's own house dust, especially that collected from the carpet in the living room, was positive. The washed skin of the yellow mealworm and the culture fluid with larvae were strongly positive in the prick-to-prick test. As negative control, the fluid without larvae was negative. The bat's hair and feces were tested as well by prick-to-prick and scratch tests; the first was negative, and the second positive. It is likely that the positive scratch test with the patients own house dust was positive because of contamination with bat feces. Total serum IgE was elevated to 533 kU/l. CAP tests were negative to house-dust mites, Chironomus, cockroaches, and animal epithelia, but positive to the grain beetle Sitophilus granarius (class 3, 4.3 kU/l). CAP analyses of the larvae and skin of T. molitor and bat feces, performed in the Department of Clinical Immunology and Transfusion Medicine at the Karolinska Hospital in Stockholm, Sweden, were dose-related positive with 10, 15, and 81 kU/l, respectively.

In conclusion, occupational exposure to insects and Chiroptera is a frequent cause of allergic disease; laboratory workers are at particular risk of sensitization. For the first time, we describe a patient who was allergic not only to a bat but also to the mealworms it was fed. The question then arises of whether the positive skin test and CAP results with bat feces were due to the content of mealworm antigens in the feces. Unfortunately, the patient refused to undergo further tests; therefore, RAST-inhibition tests were not performed.