Development of a cockroach (Blattella germanica) qPCR for the objective measurement of exposure at home

Cockroach allergens have a greater impact on asthma morbidity than those from dust mites, cats, and dogs. The American cockroach (Periplaneta americana) and the German cockroach (Blattella germanica) are most frequently responsible for sensitization. The worldwide prevalence of allergic sensitization has been estimated at 2 to 26 % and is influenced by unfavorable socioeconomic conditions. Exposure is generally measured by determining antigen levels in dust or through insect trapping. We developed a real-time quantitative PCR (qPCR) method to provide an objective measurement of B. germanica levels in dwellings. The specificity of the qPCR primers and TaqMan® hydrolysis probe was validated in silico with 18S rRNA sequences. No amplification was observed for other species of cockroaches, with the exception of Blattella nipponica, which is not common indoors. From 2018 to 2021, exposure to B. germanica was detected and quantified in 27 of 389 dwellings in Bourgogne-Franche-Comté (mean = 333.8; median = 9.1 and maximum = 5304 copy number equivalents) and in 236 of 3193 ELFE cohort dwellings in mainland France in 2011 (mean = 15.6; median < 1 and maximum = 1275 copy number equivalents). The distribution of dwellings testing positive for cockroaches (7 %) differed among the 12 regions of France: