The levels of cockroach allergen in relation to cockroach species and allergic diseases in Thai patients

Abstract

Recently, cockroaches have been established as the second most important allergen, producing allergic diseases, especially in low socio-economic populations. In Thailand, about 44-61% of atopic patients were positive to cockroach extract by a skin-prick test. This study examined cockroach allergen levels in relation to cockroach species and allergic diseases in the houses of cockroach-sensitive patients. Sixty households of allergic patients in the Bangkok metropolitan area were surveyed using open- and closed-ended questionnaires. Cockroaches were collected using commercial cockroach traps, while dust samples were obtained from the bedrooms, kitchens and living rooms of the houses using a vacuum cleaner. The cockroaches were counted and their species identified. The levels of cockroach allergens were determined by specific monoclonal antibodies using a monoclonal antibody-polyclonal antibody based sandwich ELISA kit. Six cockroach species were identified: Periplaneta americana (American cockroach, 72.15%), Supella longipalpa (2.75%, found in only one house), Periplaneta brunnea (0.78%), Periplaneta australasiae (0.78%), Neostylopyga rhombifolia (0.78%), Blattella germanica (German cockroach, 0.390%) and nymphs (22.35%). Allergens of the predominant species, P. americana, were detectable in all homes studied, with the highest levels in the kitchen areas. The range of allergen levels in house dust varied from 0.40-162.00 μg per g of dust. The median and mean allergen levels in kitchen dust were 59.16 μg and 62.80 μg per g of dust, respectively, while the median allergen level in bedroom dust was only 15.90 μg per g of dust. The German cockroach allergen (Bla g 2) was undetectable in any of the houses. In conclusion: P. americana was the most common cockroach and may be the species causing allergic diseases, especially asthma, in Thailand, which differs from the USA and Europe.