Abstract
Due to its suspected increase in host range and subsequent global diversification, Sarcoptes scabiei has important implications at a global scale for wildlife conservation and animal and human health. The introduction of this pathogen into new locations and hosts has been shown to produce high morbidity and mortality, a situation observed recently in Australian and North American wildlife.Of the seven native animal species in Australia known to be infested by S. scabiei, the bare-nosed wombat (Vombatus ursinus) suffers the greatest with significant population declines having been observed in New South Wales and Tasmania. The origins of sarcoptic mange in Australian native animals are poorly understood, with the most consistent conclusion being that mange was introduced by settlers and their dogs and subsequently becoming a major burden to native wildlife. Four studies exist addressing the origins of mange in Australia, but all Australian S. scabiei samples derive from only two of these studies. This review highlights this paucity of phylogenetic knowledge of S. scabiei within Australia, and suggests further research is needed to confidently determine the origin, or multiple origins, of this parasite.At the global scale, numerous genetic studies have attempted to reveal how the host species and host geographic location influence S. scabiei phylogenetics. This review includes an analysis of the global literature, revealing that inconsistent use of gene loci across studies significantly influences phylogenetic inference. Furthermore, by performing a contemporary analytical approach on existing data, it is apparent that (i) new S. scabiei samples, (ii) appropriate gene loci targets, and (iii) advanced phylogenetic approaches are necessary to more confidently comprehend the origins of mange in Australia. Advancing this field of research will aid in understanding the mechanisms of spillover for mange and other parasites globally.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1578-2) contains supplementary material, which is available to authorized users.
Highlights
The spread of pathogens from endemic to novel host foci, otherwise known as spillover, is one of the most significant threats to the health of both animals and humans, globally [1, 2]
More recently two studies [36, 37] based on data obtained from S. scabiei from France concluded that S. scabiei was introduced into Australia by European settlers based on a single French human S. scabiei sequence being identical to the reference S. scabiei var wombatii by 12S 16S ribosomal RNA (rRNA) gene, and clustering of French and Australian human mites based upon cytochrome c oxidase subunit 1 (COX1) sequences
General conclusions from all gene targets include that (i) microsatellites identify distinctive host separation [35, 47, 49,50,51,52], (ii) COX1 and 16S are consistent with host and location separation, with human specific mites indicating higher species separation based on location according to COX1 [32, 35, 36, 42, 53, 54], (iii) ITS-2 and 12S should only be used for S. scabiei identification and that a single species of mite infects all animals and humans [32, 34, 37, 38, 42, 53, 55, 56], and (iv) genes encoding for glutathione S-transferase-1 and voltage-sensitive sodium channels (GST1 and VSSC, respectively) might be a good indicator for host-related variation and resistance [57]
Summary
The spread of pathogens from endemic to novel host foci, otherwise known as spillover, is one of the most significant threats to the health of both animals and humans, globally [1, 2]. Skerratt et al [34] identified mites from wombats, dogs and humans in Australia to have similar 12S rRNA gene sequences and concluded that European settlers and their domestic dogs introduced mange into Australian wildlife.
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