Susceptibility To Acaricides And Genetic Diversity Of Sarcoptes Scabiei From Animals

Sarcoptes scabiei is an ectoparasite responsible for the emerging/re-emerging disease called scabies in humans or mange in animals.It was reported in 104 species across 27 families of domestic and wild animals.Current treatments for scabies/mange are limited and there are no efficient products for the environment control of S.scabiei.Moreover,the taxonomic status of S.scabiei is still under controversy and the question remains that whether it represents a single species or several taxa.The objectives of the thesis were to assess the susceptibility to acaricides and analyse the genetic diversity of S.scabiei from animals.In the first part of the thesis,an animal model was used to evaluate the efficacy of afoxolaner,a new acaricide from the isoxazoline family.The primary outcome of efficacy was based on the reduction in the number of live mites counted in skin scrapings following treatment.At day 8,all afoxolaner-treated pigs(n=4)were mite-free,while mites were still found in three of the ivermectin-treated pigs.All treated pigs were cured at the end of the study(day 50)and all pigs in the control group remained infected.Secondary outcomes included measures on the reduction of skin lesions and pruritus.The clinical lesions of scabies infection were allowed to disappear completely for all the pigs in the afoxolaner group but not in the ivermectin group at day 14 after the treatment.An increase of the pruritus was observed right after treatment,followed by a decrease of the pruritus score in both treated groups.The second part of the thesis was to evaluate the scabicidal effect of molecules or products using an in vitro test.A gradient of concentrations of ivermectin and moxidectin as well as 10 essential oils have been evaluated in vitro against S.scabiei.After 24h of exposure to ivermectin and moxidectin,the median lethal concentrations were 150.2±31.4 ng/mL and 608.3±88.0 ng/mL,respectively.Doses of ivermectin under 1 ng/mL and moxidectin under 10 ng/mL showed no scabicidal effect.Fumigation and contact bioassays were used for the assessment of essential oils efficacy.Among lavender,tea tree,geranium,clove,eucalyptus,manuka,japanese cedar,palmarosa and bitter orange tested with the contact bioassay,the clove oil demonstrated the best scabicidal effect(1%solution killed all the mites within 20 min).Among the 9 essential oils listed before plus cade with the fumigation bioassay,tea tree oil demonstrated the best scabicidal effect(all the mites died within only 4 min).For environmental control of S.scabiei,the efficacy of biocides or repellents was assessed.The median survival time was calculated for permethrin(4%and 0.6%),esdepallethrin and bioresmethrin,bifenthrin,cypermethrin and imiprothrin,cyfluthrin,tetramethrin and sumithrin,DEET(25%and 50%),icaridin and IR3535.The third part of the thesis included the study of the genetic diversity of populations of S.scabiei from animals.A part of COX1 was used for phylogenetic analyses.The results showed that Sarcoptes mites from humans seem to derive from dogs.