Recovery of Dermatophagoides pteronyssinus (Acariformes: Astigmata: Pyroglyphidae) is influenced by vacuuming protocol, fabric type and the viability of dust mites

Dermatophagoides pteronyssinus (Trouessart, 1897) (Acariformes: Astigmata: Pyroglyphidae) is amongst the most common house dust mites (HDMs) species in Europe. Vacuuming is commonly employed as a method for the recovery for the subsequent quantification of mite densities. The vacuuming protocols employed and their efficiencies are frequently unreported. In this study, a constant-flow vacuum sampler was used to evaluate the recovery of laboratory-reared D. pteronyssinus from cotton, denim or fleece. Two vacuuming protocols were employed. Protocol 1 (P1) entailed a single unidirectional pass of the vacuum head across the fabrics for 60, 90 or 120 seconds. For Protocol 2 (P2), fabrics were vacuumed twice (laterally followed by diagonally) for the same time periods. Vacuuming was carried out on fabrics seeded with live mites (LM), dead mites (DM), and live mites, which were applied to fabric surfaces for 10 minutes and then euthanized by freezing prior to vacuum sampling (EM). There was a significant difference (P<0.001) in mean HDMs recovery with regard to mite viability (LM, DM, EM), fabric type (cotton, denim, fleece), duration of sampling (60, 90, 120s) and vacuuming protocols employed (P1, P2). The numbers of mites recovered from fleece (compared to cotton and denim) were lower for each treatment type where LM and EM were deployed. Overall, the use of protocol 2 resulted in the greatest mean percentage recovery (>80%) of dust mites for all fabrics combined. Recovery rates were also influenced by entrapment of mites (or active attachment) in the fabric microstructure within the weave. The results have implications for the standardisation of mite recovery from fabrics by means of vacuuming.