Longitudinal Evidence of Increasing In Vitro Tolerance of Scabies Mites to Ivermectin in Scabies-Endemic Communities

Abstract

Scabies remains a prominent cause of morbidity in remote Aboriginal communities in northern Australia. Secondary bacterial infection of skin lesions caused by scabies is linked to high rates of rheumatic fever and rheumatic heart disease in affected communities.1 Because the sustainability of community scabies eradication programs using topical permethrin, 5%, is problematic, oral ivermectin has been proposed as an alternative acaricide for mass drug administration. While ivermectin is used routinely for the management of crusted scabies (CS) in northern Australia, reports of clinical and in vitro resistance2 indicate that prospective monitoring is required to detect the further emergence of ivermectin resistance. Herein, we report the results of a longitudinal study of in vitro acaricide sensitivity of Sarcoptes scabiei to ivermectin in a region under increasing drug selection pressure.