A Tractable Experimental Model for Study of Human and Animal Scabies

Abstract

Background:Scabies is a parasitic skin infestation caused by the burrowing miteSarcoptes scabiei. It is common worldwideand spreads rapidly under crowded conditions, such as those found in socially disadvantaged communities of Indigenouspopulations and in developing countries. Pruritic scabies lesions facilitate opportunistic bacterial infections, particularlyGroup A streptococci. Streptococcal infections cause significant sequelae and the increased community streptococcalburden has led to extreme levels of acute rheumatic fever and rheumatic heart disease in Australia’s Indigenouscommunities. In addition, emerging resistance to currently available therapeutics emphasizes the need to identify potentialtargets for novel chemotherapeutic and/or immunological intervention. Scabies research has been severely limited by theavailability of parasites, and scabies remains a truly neglected infectious disease. We report development of a tractablemodel for scabies in the pig,Sus domestica.Methodology/Principal Findings:Over five years and involving ten independent cohorts, we have developed a protocol forcontinuous passage ofSarcoptes scabieivar.suis. To increase intensity and duration of infestation without generating animalwelfare issues we have optimisedan immunosuppression regimenutilising daily oral treatment with 0.2mg/kg dexamethasone.Only mild, controlled side effects are observed, and mange infection can be maintained indefinitely providing large mite numbers(.6000 mites/g skin) for molecular-based research on scabies. In pilot experiments we explore whether any adaptation of the mitepopulation is reflected in genetic changes.Phylogenetic analysis was performed comparing sets of genetic data obtained from pigmites collected from naturally infected pigs with data from pig mites collected from the most recent cohort.Conclusions/Significance:A reliable pig/scabies animal model will facilitatein vivostudies on host immune responses toscabies including the relations to the associated bacterial pathogenesis and more detailed studies of molecular evolutionand host adaption. It is a most needed tool for the further investigation of this important and widespread parasitic disease.