Studies On Pyrethroid Resistance In Cimex Lectularius (Hemiptera: Cimicidae), In Berlin, Germany

Abstract:
Pyrethroid-resistance in bed bugs, Cimex lectularius, has been described in many countries, but up to now, for Germany no data are available. However, pest control companies increasingly report difficulties in controlling bed bugs with pyrethroids. In the present study four bed bug strains were collected from infested apartments in Berlin and reared in the laboratory without insecticide selection pressure. In this work bed bug colonies are referred to as strains, which denotes their origin but individuals within a strain and not genetically uniform. A filter contact bioassay was developed and susceptibility of the collected bed bug strains against deltamethrin was determined in comparison to a pyrethroid susceptible laboratory strain. Resistance ratios, calculated from LD50-values were between Rr 3.8 and Rr 5.1. Molecular studies regarding two mutations V419L and L925I in the voltage gated sodium channel α‑subunit gene, which have been reported to be involved in knockdown resistance (kdr) in bed bugs collected from the USA, were also performed. Pyrosequencing of genomic DNA fragments showed the presence of mutation L925I in each of the four studied field populations with allele frequencies between 30% and 59%, while it was not detectable in the laboratory strain. Furthermore, none of the tested strains had the substitution V419L. The results demonstrate that decreased pyrethroid susceptibility of bed bugs is present in Germany but resistance levels are considerably lower than reported from the USA and Australia.