Gene silencing in Sarcoptes scabiei

Thais Rodrigues, Ph.D. is a postdoctoral scholar at the University of Kentucky’s Entomology Department where she is investigating RNAi to Manage Wood-Feeding Pests, Emerald Ash Borer and Asian Long-horned Beetle: The Next Generation of Pest Management.   MORE ABOUT THE AUTHOR

“Gene silencing by RNA interference in Sarcoptes scabiei: a molecular tool to identify novel therapeutic targets” is an original research publication in Parasites & Vectors. In this paper, Fernando and colleagues have reported some results that may potentially facilitate future research towards developing novel intervention methods to control scabies. Of considerable medical relevance, this parasitic mite is responsible for severe skin infections and complications due to mite association with secondary infections.

Sarcoptes scabiei, the itch mite. Image credit. Kalumet, This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Mainly occurring in economically disadvantaged populations, only a few broad-spectrum anti-parasitic drugs are available to treat scabies. However, these drugs have limitations that often fail to control the disease, such as their specificity to ovicidal activity and their short half-lives. As an alternative, Fernando and colleagues indicate potential benefits of silencing S. scabiei target genes using RNA interference (RNAi).

RNAi technology has allowed the study of gene function in several arthropods and facilitated the identification and selection of potential target molecules to manage these organisms. The authors limit their attention to identifying 12 key genes of the RNAi pathway in S. scabiei varieties from canine, porcine and human hosts, and successfully silence a target gene in S. scabiei var. suis. For that, genome databases were assessed and a non-invasive delivery method of dsRNA was developed.

Image result for itch mites

Typical symptoms of an itch mite infestation

As expected, they found substantial genomic evidence of the presence of a complete RNAi machinery in S. scabiei. Notably, the genes piwi, c3po and r2d2 were not detected, which, according to the authors, do not indicate that the genes are absent in S. scabiei. Another indicative that corroborate with authors suggestion is the successful reduction of the target gene expression after dsRNA exposure.

After facing a big challenge of establishing a continuous in vitro culture with precise mimicking of the epidermal conditions, two approaches were used to support the presence of the RNAi machinery in S. scabiei. First, ingestion of labeled dsRNA demonstrates that S. scabiei can successfully take up the molecules to their gut. Additionally, the expression level of the target gene shows a reduction of 35% after dsRNA exposure, considered by the authors indicative of a strong RNAi effect.

human itch miteAs future directions, Fernando and colleagues consider RNAi technology a highly attractive experimental approach to test potential drug and vaccine as well as topical treatments targeting the scabies mite. Double-stranded RNA targeting essential genes for regulating interactions between parasites and their hosts, and essential genes for mite survival would reduce the S. scabiei numbers in an acute infection. Also, the RNAi could be used to inform on the potential of candidate genes as novel intervention targets.

Fernando DD, Marr EJ, Zakrzewski M, Reynolds SL, Burgess STG, Fischer K. (2017) Gene silencing by RNA interference in Sarcoptes scabiei: a molecular tool to identify novel therapeutic targets. Parasites & Vectors201710:289 DOI: 10.1186/s13071-017-2226-1




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