Scabies is amongst the commonest dermatological conditions globally, imposing a considerable economic burden on individuals, communities and health systems. Substantial epidemiological evidence shows that in tropical regions scabies is often linked to pyoderma. Patients can develop serious illness due to invasion by opportunistic bacteria such as cellulitis, heart and kidney diseases, bacteraemia and sepsis. The health burden due to complicated scabies in resource-poor Australian Aboriginal and Torres Strait Islander communities is extreme. Two projects will be discussed:
(1) The molecular mechanisms that underpin the link between scabies and bacterial pathogens were unknown. We proposed that scabies mites play a role in the establishment, proliferation and possibly transmission of opportunistic pathogens. Our recent work showed that by releasing complement inhibitors into the skin, scabies mites promote the growth of pathogens in their vicinity. We investigated in detail the impact of scabies mite complement inhibitors on the growth of the two most recognised mite associated pathogens Streptococcus pyogenes and Staphylococcus aureus.
(2) The diversity and dynamics of microbes associated with scabies mites have not been investigated. It is also unknown whether scabies mites require endosymbionts for survival.
This project aims to assess the impact of a scabies mite infection on the host skin microbiota. First we demonstrated experimentally in a longitudinal study using a porcine model that scabies mites drastically altered the healthy skin microbiota. We observed a shift of pathogenic over benign bacteria persisting beyond acaricide treatment and healing of the skin lesions. Based on this pilot study we now sequence the microbiomes associated with scabies mites in patients from Northern Australia, France and India.
These data will provide the molecular data for translational research into novel treatment strategies and policies for the prevention and control of this insidious disease.