i76 Berlin beetle (Khapra beetle)

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The distribution of the beetle is worldwide, having been introduced in Germany in the 1930s from South America via the USA. It is considered to be a major pest in central Europe and has been reported to be a common pest in Berlin. (1)

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Central heating is a prerequisite for survival of this desert insect, which thrives in food storage areas, larders and dining rooms. The Berlin beetle is known to be a common pest in Berlin households, where several studies have been conducted. It is also found in contaminated feeds and cereals, thus giving it the status of an occupational allergen. The exposure includes both beetle and larvae.(1, 2) The spear-shaped hairs of larval skins may be the location of allergenic structures.

The closely related species T. variabile (also known as the warehouse or cabinet beetle) is known to infest food warehouses and processing plants. Although it feeds on almost anything, it prefers wheat, barley, or rice, and it is very difficult to eradicate because it can slow or accelerate its reproduction cycle based on the amount of food readily available. Trogoderma is very resistant to extreme temperature changes in the larval or adult stages. As a result, workers in these facilities inevitably have increased exposure to these insects, the by-products of which may also enter the human food chain. (3)

IgE-mediated reactions

Sensitisation has been shown in perennial asthma and rhinitis patients,(4)  where asthmatics reacted more severely to the skin test than patients with rhinitis. (1, 2) Exposure and sensitization includes both beetle and larvae. (1, 2, 5)

The beetle was reported to be a common pest in Berlin, with approximately 35% positive reaction to Trogoderma-extract in patients with known inhalation allergy. (1, 2)

The most common setting for sensitisation is likely to be occupational. A case of chronic bronchial asthma attributed to T: angustum was described, exposure having included both the beetles and larvae. (5)

Similarly, occupational allergy was described to the closely related species T. variabile, in a 42-year-old male machinist in a pet-food manufacturing plant who presented with shortness of breath, chest tightness, and conjunctivitis immediately after airborne dust exposure created while cleaning a conveyor belt system. Prior to onset of symptoms, he had worked at this facility for 4 years. His FEV1 had decreased and showed no improvement after bronchodilator use. Results of skin-prick tests with seasonal and perennial allergens were completely negative. A dust sample from the workplace revealed warehouse beetle, and subsequent skin-prick tests with warehouse beetle extracts were positive. A titration nasal challenge to warehouse beetle dust extract prepared from the warehouse dust sample using acoustic rhinometry revealed a dramatic decrease in cross-sectional area and nasal volume after challenge. Patient serum contained specific IgE to 15 different proteins in samples prepared from warehouse beetle materials. IgE binding was not observed to dust mite, storage mite, or cockroach extract proteins. (3)

No allergens have yet been identified.

The authors suggested that the major sensitising allergen in the worker was derived from beetle exoskeletons, which was supported by the presence of specific IgE to a single protein of 31.3 kDa present in the authentic exoskeleton extract. This protein was also present in authentic adults, larvae, and faeces extracts. (3)

Cross-reactivity

No cross-reactivity has been reported between T. angustum and cockroaches, although cross-reactivity is known in insects. (2)

Last reviewed:April 2022