Authors

J Cotton²; E Harris²; J McIntyre²; M Pazmino Betancourth²; F Baldini²; E Geddes¹; K Bartley¹; J Hearn³; A Nisbet¹; R Laing²; S Burgess¹;  ¹ Moredun Research Institute, UK;  ² School of Biodiversity, One Health and Veterinary Medicine, University of Glasgow, UK;  ³ Centre for Epidemiology and Planetary Health, School of Veterinary Medicine, SRUC (Scotland’s Rural College), UK

Discussion

Sheep scab is caused by infestation with the ectoparasitic mite, Psoroptes ovis. It is a highly contagious disease with serious welfare implications for affected animals and a large economic burden for the industry from treatment costs and production losses. Control currently relies on only two treatment options: plunge dipping with organophosphate (OP) acaricides, which is effective but has significant environmental and safety concerns, and injectable macrocyclic lactones (MLs), which are widely used but are impacted by emerging resistance. Resistance to pesticides in arthropods frequently involves changes in the thickness and composition of the cuticle. While this mechanism has not been reported for ML resistance, cuticle changes in response to other treatments have been reported in plant-parasitic mites. In addition, two cuticle proteins were recently identified as being overexpressed in response to ML exposure in ML-resistant Psoroptes mites from cattle. We have been comparing ML-resistant (R) and sensitive (S) mite isolates as part of a project investigating the genetic basis of drug resistance to MLs in P. ovis. Using mid infra-red spectroscopy (MIRS), we have identified spectral differences between R and S mites that may be linked to differences in cuticle structure or composition associated with ML resistance. MIRS has previously been shown to predict cuticular resistance in mosquitos. We now aim to validate this result using microscopy and then investigate whether MIRS signatures segregate with resistance in a genetic cross between the R and S isolates that we have generated.