Indoor allergens and endotoxins in relation to cockroach infestations in low-income urban homes.

Background: Cockroach allergens are well recognized as important risk factors in the development and prevalence of allergic rhinitis and asthma in children, especially in low-income urban households. The German cockroach gut hosts a diverse community of highly abundant microbes, including gram-negative bacteria that shed large amounts of endotoxins in cockroach feces. Objective: We sought to delineate the causal relationship between the presence of cockroaches in homes and levels of household endotoxins. Methods: In laboratory assays, we measured the amount of endotoxin produced by cockroaches. In-home monitoring estimated the size of the cockroach population in each home and quantified cockroach allergen Bla g 2 and endotoxin levels in household dust and on heating, ventilating, and air-conditioning (HVAC) filters. An environmental intervention was implemented in a subset of the infested homes to eliminate cockroaches. Bla g 2 and endotoxin levels were quantified for 6 months after the intervention. Results: Large amounts of endotoxin are excreted by female (2900 endotoxin units [EU]/mg feces) and male (1400 EU/mg) cockroaches. At baseline, household dust and HVAC filters in infested homes had significantly higher levels of allergen (Bla g 2) and endotoxin than uninfested homes. Environmental intervention resulted in significant declines in cockroaches as well as allergen and endotoxin levels. In contrast, cockroach numbers and allergen and endotoxin concentrations remained high in infested-control homes. Conclusions: Cockroaches are a significant source of both endotoxins and potent allergens, potentially resulting in coexposure of asthmatic children to both.