Mealworm
Summary
An occupational allergen, which may result in allergy symptoms in sensitised individuals.
Clinical Relevance
IgE-mediated reactions
Mealworm may commonly induce symptoms of occupational allergy in sensitised individuals; the symptoms include asthma, rhinoconjunctivitis, and urticaria. The organism affects fishermen, grain handlers, and pet shop workers. As the larvae are used as live fish bait, they are an especially common source of allergy for anglers, and for persons with similar, but occupational, exposure. The inhaled particulates derived from the exoskeletons of Mealworm larvae are potent sensitisers and can induce IgE-mediated occupational asthma in fish handlers. The same source reports anaphylaxis following the ingestion and inhalation of Mealworm.
However, the main group of workers exposed to allergens from Mealworm are workers on live bait farms and resellers of live bait. Immediate-onset asthma, rhinitis, and/or contact urticaria have been reported in 4 of 5 bait handlers, from unwrapping and packaging the larvae in a warehouse. The presence of skin-specific IgE to Mealworm extract was demonstrated in all 4 symptomatic workers. Serum-specific IgE against Mealworm antigens was demonstrated in the 2 workers with asthma. Bronchial provocation challenge with Mealworm performed on the 2 workers with asthma resulted in an immediate fall in FEV1 of more than 20%.
In a study of 50 live fish bait farm workers, 8 retailers and 18 laboratory workers exposed to live fish bait, sensitisation to live fish bait was found in 24 workers (31.6%), and 7 (9.2%) reported work-related symptoms (3 reported asthma, 5 rhinoconjunctivitis, and 1 contact urticaria). Five were skin-specific IgE test-positive and found to have serum-specific IgE to one or more live fish bait extracts. One was also exposed to live fish bait while fishing. Serum-specific IgE was raised to bluebottle in 3, to bee moth in 3, to Mealworm in 1, and to gusano rojo in 2.
In a study of 14 subjects with respiratory symptoms associated with exposure to live fish bait, skin- and serum-specific IgE tests with Lucilia caesar, Galleria mellonella, and Tenebrio mollitor extracts were conducted. Thirteen subjects had asthma, all 14 had rhinoconjunctivitis, and 3 had contact urticaria. Eleven subjects had respiratory symptoms after fishing with live bait, and 3 subjects had symptoms during their work in a commercial fish bait farm. The presence of skin- or serum-specific IgE to L. caesar extract was demonstrated in 13 subjects, to G. mellonella extract in 4 subjects, and to T. mollitor extract in 3 subjects. After exposure to live fish bait, 2 subjects had an early asthmatic response, 3 had a late asthmatic response, and 2 had no asthmatic response. Late asthmatic response was associated with a long-lasting increase in bronchial responsiveness.
A 24 year-old female employed in a pet shop developed occupationally related asthma, rhinoconjunctivitis and contact urticaria following exposure to Yellow mealworm (Tenebrio mollitor), which was being sold as food for birds and reptiles. The presence of Mealworm skin-specific IgE was demonstrated, and a histamine release test was positive to Mealworm wholebody extract.
A 26-year-old woman who worked as an animal handler, which included feeding the animals Mealworm beetles that were raised in wheat bran, experienced work-related rhinoconjunctivitis on exposure to this insect. Skin-specific IgE tests with extracts prepared from the larval, pupal, and adult-life stages were positive for the patient and for another individual with allergy to a closely related species of beetle, Alphitobius diaperinus (Lesser Mealworm). The presence of serum-specific IgE to Mealworm was demonstrated.
Occupational allergic rhinitis and asthma following exposure to bats in a 31-year-old scientist was reported and found to be caused by sensitisation to the Mealworms that she was feeding them.
A 47-year-old African-American female elementary schoolteacher presented with itchy, watery eyes, rhinorrhoea, postnasal drainage, and nasal congestion complicated by recurrent epistaxis for 2 months. She had had similar symptoms the previous year from September to May, but was symptom-free during the summer. Her symptoms began within 1 hour after entering the classroom and improved in the evening at home, on weekends, and vacation. A detailed history of her classroom environment revealed the presence of Mealworms that were used to teach the children about life cycles. A skin-specific IgE test was positive and associated with a delayed reaction, starting 8 hours after exposure and persisting for 24 hours. Removal of the Mealworms from the classroom resulted in complete relief of her symptoms.
Cross-Reactivity
The allergen For t 1, from F. taiwana (biting midge), was shown to have significant sequence identity with triosephosphate isomerase of Anopheles merus, Tenebrio mollitor, and Ochlerotatus togoi. The clinical significance of this relationship was not evaluated.
RAST inhibition studies have demonstrated immunologic cross-reactivity among the life stages of T. mollitor, and also between T. mollitor and Alphitobius diaperinus (Lesser mealworm), as well as a slight cross-reactivity with blowfly.
References
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