The cascading pathogenic consequences of Sarcoptes scabiei infection that manifest in host disease

Making the most of mortalities: Novel host-parasite records in a sandy inland mouse (Pseudomys hermannsburgensis)

From 2020 to 2022, systematic investigation of wildlife mortalities on Dirk Hartog Island, Western Australia was initiated to inform wildlife disease risk analyses for translocation purposes. As part of this monitoring, in November 2020, a sandy inland mouse (Pseudomys hermannsburgensis) was found deceased with multiple comorbidities. Gross necropsy, histopathology and ancillary molecular testing identified several novel host-parasite associations. Sarcoptes scabiei was identified via molecular methods in association with consistent cutaneous pathology, representing the first known detection of this parasite in an Australian native rodent. A putative novel virus belonging to the subfamily Gammaherpesvirinae was also identified, representing the first known detection of a herpesvirus (Orthoherpesviridae) from this species, although it was not clearly associated with other disease processes. A heavy burden of the cestode Hymenolepis microstoma was also present in the gastrointestinal tract, representing a new host record for this species, whilst a pancreatic adenocarcinoma was also found. Beyond the novelty of these host records, these findings contribute to important health baselines of rodent populations on Dirk Hartog Island and highlight the value of investigating mortalities and implementing health surveillance as part of ecological monitoring and wildlife translocation projects.

Effect of the sarcoptic mange upon metabolome profiling in wild boars

Sarcoptic mange is a highly contagious disease and represents one of the main health concerns for humans and non-human mammals worldwide. It is caused by the mite Sarcoptes scabiei and can course with different morphological and physiological presentations. Accordingly, aside from skin inflammation, hosts may experience changes in body condition, immune system, biochemistry, reproduction, and thermoregulation, although the understanding of the downstream metabolic burden is still missing. In this context, mange-derived fat store depletion and following imbalance of fatty acid composition might contribute to the severity of the illness. The lack of a tool for early detection of this etiological agent often results in significant financial losses for farmers and harm to animal welfare. Therefore, using targeted LC-MS/MS-based metabolomics approach, we sought to investigate the impact of sarcoptic mange upon metabolome profiling in the blood serum of mangy wild boars. Thirteen wild boars were analyzed in three different clinical conditions, namely when they were sick, during the therapeutic treatment with ivermectin, and when they were deemed recovered from the disease. We identified specific long-chain acylcarnitines highly abundant in the blood serum of the subjects within the infection phase, when compared to the ivermectin-treated and healthy conditions. Overall, data from our preliminary study highlighted the need for more accurate and broad-based studies, about the potential role of the long chain acylcarnitines in the metabolic homeostasis, to help early diagnose of the sarcoptic mange.

Genetic and Serological Survey of Sarcoptic Mange (Sarcoptes scabiei) in Wild Boars (Sus scrofa) in South Korea

Sarcoptic mange, caused by Sarcoptes scabiei, has been reported in various wildlife species, with the potential to impact populations. While it has been documented in some wildlife species and domestic animals, it has not been previously reported in wild boars in South Korea. In March and April 2022, skin samples from nine wild boars and one raccoon dog with suspected sarcoptic mange were submitted to the NIWDC. These samples were tested and confirmed the presence of S. scabiei in six wild boars and one raccoon dog. Genetic analysis of the cox-1 gene from mites indicated that the gene was identical and belonged to the same haplotype in both host species. Serological survey of 658 wild boars, collected from March 2022 to February 2023, revealed a nationwide seroprevalence of 5.47%. The highest seroprevalence was in Gyeongsangnam-do (9.82%); however, regional differences in seroprevalence across the country were not statistically significant, suggesting the disease may be endemic across South Korea. Seroprevalence was highest in spring (16.84%), likely due to increased contact during winter. This study provides fundamental data on the genetic characteristics and distribution of S. scabiei mites in South Korean wild boars, emphasizing the need for continued surveillance to prevent further spread.

Epidemiological factors conditioning sarcoptic mange spreading in wild boar (Sus scrofa)

Sarcoptic mange is a widely distributed disease, with numerous potential hosts among domestic and wild animals. Nowadays it is considered a neglected re-emergent infection in humans. As a difference with domestic pigs, and even with several clinical cases reported in some European countries, it seems that Eurasian wild boars (Sus scrofa) have a low susceptibility to clinical mange. However, because of a case of confirmed transmission from Spanish ibex (Capra pyrenaica) to wild boar in the province of Tarragona, we planned a large-scale ELISA survey in the neighboring Valencian Community (SE Spain). We compared 419 wild boar sera from different management systems (fenced vs. open game estates), different ages (piglets, juveniles, and adults), with different behaviour (gregarious females of all ages and male piglets vs. solitary juveniles and adult males), from areas with different wild boar densities, different wild ruminant densities and different sarcoptic mange epidemiologic situations. The whole prevalence of antibodies against sarcoptic mange in the tested wild boars was 10.5%. No significant differences were found when comparing fenced and free ranging wild boars, males and females, gregarious vs. solitary individuals or among different ages. However, wild boar density was a relevant factor. In areas with a hunting bag of <1 wild boar/km2, considered as a low density of suids, the seroprevalence was 2.94%, but rose to 11.52% in high density districts, constituting a significant difference (p = 0.037). Low wild boar populations would act as a protective factor (OR 0.233; p = 0.049) against coming into contact with the mite. The wild ruminant densities or their sarcoptic mange status did not show any effect on wild boars seroprevalence against this disease. These results reinforce the suggested host-taxon Sarcoptes scabiei specificity and the independence of host-species foci.

A retrospective epidemiological study of sarcoptic mange in koalas (Phascolarctos cinereus) using wildlife carer admission records

Outbreaks of sarcoptic mange are sporadically reported in koala populations across Australia, but disease characteristics (e.g., distribution across the body) remain poorly understood. In an area of Northern Victoria regular cases coming into care suggest mange may have become enzootic, and here we characterise those koala mange admission records. In 18% (n = 10) of mange affected koala reports that had a recorded outcome (n = 55), the animals died before the carers could locate them, and of the remaining 45 koalas that were alive upon carer arrival, 80% (n = 36) had to be euthanised due to severe mange. The number of admissions varied among years (highest observed in 2019), and over 60% of affected koala admissions were male. Male admissions peaked in austral spring and again in late austral summer-autumn (mating and birthing seasons), with female admissions only exhibiting the latter peak (birthing season). Fissures of the epidermis of the front paws occurred in 100% of admitted koalas, with 70% also showing these signs elsewhere on ventral surfaces or limbs. Only male koalas had signs of mange on the chest and face, and only female koalas had signs of mange on their back. Collectively, this study suggests sarcoptic mange can be a severe disease in koalas, and that male koalas may play an important role in seasonal transmission dynamics. We discuss how these findings may help inform intervention strategies.

Changes in the Skin Microbiota in Two Bare-nosed Wombats (Vombatus ursinus) with Differing Recovery Trajectories following Treatment for Sarcoptic Mange

We report tracking of bacterial skin microbiota for two bare-nosed wombats (Vombatus ursinus) following in situ treatment for sarcoptic mange. Sarcoptes scabiei, the etiologic agent, has dramatic effects on skin microbiota. Our case reports show differing disease trajectory and bacterial beta diversity between the two treated individuals.

The effects of spatially-constrained treatment regions upon a model of wombat mange

The use of therapeutic agents is a critical option to manage wildlife disease, but their implementation is usually spatially constrained. We seek to expand knowledge around the effectiveness of management of environmentally-transmitted Sarcoptes scabiei on a host population, by studying the effect of a spatially constrained treatment regime on disease dynamics in the bare-nosed wombat Vombatus ursinus. A host population of wombats is modelled using a system of non-linear partial differential equations, a spatially-varying treatment regime is applied to this population and the dynamics are studied over a period of several years. Treatment could result in mite decrease within the treatment region, extending to a lesser degree outside, with significant increases in wombat population. However, the benefits of targeted treatment regions within an environment are shown to be dependent on conditions at the start (endemic vs. disease free), as well as on the locations of these special regions (centre of the wombat population or against a geographical boundary). This research demonstrates the importance of understanding the state of the environment and populations before treatment commences, the effects of re-treatment schedules within the treatment region, and the transient large-scale changes in mite numbers that can be brought about by sudden changes to the environment. It also demonstrates that, with good knowledge of the host-pathogen dynamics and the spatial terrain, it is possible to achieve substantial reduction in mite numbers within the target region, with increases in wombat numbers throughout the environment.

Resolution of Clinical Signs of Sarcoptic Mange in American Black Bears (Ursus americanus), in Ivermectin-Treated and Nontreated Individuals

The parasitic mite Sarcoptes scabiei causes mange in nearly 150 species of mammals by burrowing under the skin, triggering hypersensitivity responses that can alter animals' behavior and result in extreme weight loss, secondary infections, and even death. Since the 1990s, sarcoptic mange has increased in incidence and geographic distribution in Pennsylvania black bear (Ursus americanus) populations, including expansion into other states. Recovery from mange in free-ranging wildlife has rarely been evaluated. Following the Pennsylvania Game Commission's standard operating procedures at the time of the study, treatment consisted of one subcutaneous injection of ivermectin. To evaluate black bear survival and recovery from mange, from 2018 to 2020 we fitted 61 bears, including 43 with mange, with GPS collars to track their movements and recovery. Bears were collared in triplicates according to sex and habitat, consisting of one bear without mange (healthy control), one scabietic bear treated with ivermectin when collared, and one untreated scabietic bear. Bears were reevaluated for signs of mange during annual den visits, if recaptured during the study period, and after mortality events. Disease status and recovery from mange was determined based on outward gross appearance and presence of S. scabiei mites from skin scrapes. Of the 36 scabietic bears with known recovery status, 81% fully recovered regardless of treatment, with 88% recovered with treatment and 74% recovered without treatment. All bears with no, low, or moderate mite burdens (<16 mites on skin scrapes) fully recovered from mange (n=20), and nearly half of bears with severe mite burden (≥16 mites) fully recovered (n=5, 42%). However, nonrecovered status did not indicate mortality, and mange-related mortality was infrequent. Most bears were able to recover from mange irrespective of treatment, potentially indicating a need for reevaluation of the mange wildlife management paradigm.

The Distinctive Biology and Characteristics of the Bare-Nosed Wombat (Vombatus ursinus)

The bare-nosed wombat is an iconic Australian fauna with remarkable biological characteristics and mythology. This solitary, muscular, fossorial, herbivorous marsupial from southeast Australia has continent and continental island subspeciation. Vombatiformes also contains hairy-nosed wombats (Lasiorhinus spp.); koala (Phascolarctos cinereus); and extinct megafauna, Phascolonus gigas (giant wombat), Diprotodon, and Thylacoleo (marsupial lion). Culturally important to Aboriginal people, bare-nosed wombats engineer ecosystems through digging, grazing, and defecation. Olfaction and cubic fecal aggregations appear critical for communication, including identity, courtship, and mating. Though among the largest fossorial herbivores, they have a nutrient-poor diet, a home range up to an order of magnitude smaller than expected, and a metabolism among the lowest extreme for mammals >10 kg. Metabolic depression may confer advantages over resource competitors and fossorial lifestyle protection from predators, fires, and climatic extremes. Bare-nosed wombats are loved and persecuted by European colonists. Recent population increases may reflect softening attitudes toward, and greater protections of, bare-nosed wombats.

Camera traps reveal a high prevalence of sarcoptic mange in red foxes from northern Spain

The mite Sarcoptes scabiei affects numerous mammal species causing the sarcoptic mange, a widespread disease with relevance for wildlife conservation, welfare, and management. The red fox (Vulpes vulpes) could become infested by direct and indirect routes leading to external skin lesions potentially recognizable by devices such as camera traps (CTs). In the present study, 86 randomly placed CTs were used to investigate the apparent prevalence and severity of S. scabiei in a red fox population from northern Spain. Their potential environmental and population-related drivers were also assessed. A total of 341 independent encounters were examined to visually identify mange-compatible lesions. The apparent prevalence was 19.16% (confidence interval (CI) 95%: 15.08-23.80) of which 82.81% (CI95%: 71.33-91.10) were severe. Our results revealed that habitat attributes such as lower altitudes, higher coverage of water-linked habitats and woodland predominance, were significant predictors of the apparent risk of mange. The models also suggested that the apparent prevalence of mange was associated with poor body condition and elevated frequencies of spatial coincidence among fox encounters, which facilitates indirect transmission. Interestingly, we did not observe mange-compatible lesions in other sympatric wild species (>15,000 encounters examined). This could be explained by the mite's host specificity and the low probability that these other potential hosts use sites where transmission among foxes usually occurs, such as dens. This study illustrates how camera trapping can be used as an interesting tool for the surveillance of wildlife diseases, thus overcoming the logistic constraints derived from direct sampling and allowing the early detection and better management of pathogens in the riskiest areas.

Host, environment, and anthropogenic factors drive landscape dynamics of an environmentally transmitted pathogen: Sarcoptic mange in the bare-nosed wombat

Understanding the spatial dynamics and drivers of wildlife pathogens is constrained by sampling logistics, with implications for advancing the field of landscape epidemiology and targeted allocation of management resources. However, visually apparent wildlife diseases, when combined with remote-surveillance and distribution modelling technologies, present an opportunity to overcome this landscape-scale problem. Here, we investigated dynamics and drivers of landscape-scale wildlife disease, using clinical signs of sarcoptic mange (caused by Sarcoptes scabiei) in its bare-nosed wombat (BNW; Vombatus ursinus) host. We used 53,089 camera-trap observations from over 3261 locations across the 68,401 km2 area of Tasmania, Australia, combined with landscape data and ensemble species distribution modelling (SDM). We investigated: (1) landscape variables predicted to drive habitat suitability of the host; (2) host and landscape variables associated with clinical signs of disease in the host; and (3) predicted locations and environmental conditions at greatest risk of disease occurrence, including some Bass Strait islands where BNW translocations are proposed. We showed that the Tasmanian landscape, and ecosystems therein, are nearly ubiquitously suited to BNWs. Only high mean annual precipitation reduced habitat suitability for the host. In contrast, clinical signs of sarcoptic mange disease in BNWs were widespread, but heterogeneously distributed across the landscape. Mange (which is environmentally transmitted in BNWs) was most likely to be observed in areas of increased host habitat suitability, lower annual precipitation, near sources of freshwater and where topographic roughness was minimal (e.g. human modified landscapes, such as farmland and intensive land-use areas, shrub and grass lands). Thus, a confluence of host, environmental and anthropogenic variables appear to influence the risk of environmental transmission of S. scabiei. We identified that the Bass Strait Islands are highly suitable for BNWs and predicted a mix of high and low suitability for the pathogen. This study is the largest spatial assessment of sarcoptic mange in any host species, and advances understanding of the landscape epidemiology of environmentally transmitted S. scabiei. This research illustrates how host-pathogen co-suitability can be useful for allocating management resources in the landscape.

Fine-Scale Landscape Epidemiology: Sarcoptic Mange in Bare-Nosed Wombats (Vombatus ursinus)

Landscape epidemiology provides a valuable framework to interpret, predict, and manage spatiotemporal patterns of disease. Yet, owing to the difficulty of detecting pathogen occurrence in free-ranging wildlife, disentangling the factors driving disease dynamics remains a considerable challenge, particularly at fine spatial scales. Here, we investigated the fine-scale landscape epidemiology of sarcoptic mange—a visually apparent disease caused by the mite Sarcoptes scabiei—in bare-nosed wombats (Vombatus ursinus), by: (1) characterizing the distribution and density of wombats within the landscape and (2) examining the effect of environmental variation on the occurrence and apparent prevalence of mange. Wombats were heterogeneously distributed over 19.4 km of transect space (0.096–1.39 wombats ha−1) and seven months of time (increasing by a factor of 1.76). Wombat density was negatively associated with distance to vegetation cover, supporting a general propensity for wombats to occur and burrow near vegetation (native and exotic, excluding pasture). The apparent prevalence of mange varied spatially (3.1–37.5%), with the probability of disease greater in wombats with minimal vegetation and low-lying pans in their estimated home range. We observed trends of increased prevalence in areas with more burrows available per wombat and in individuals occurring near vegetation cover (although not within their home range). Wombat density and active burrow density did not influence the prevalence of mange. This research emphasizes the fine scale at which spatiotemporal patterns of disease can manifest and is the first to investigate the influence of host density for any species with indirect transmission of S. scabiei. Collectively, our results suggest that individuals inhabiting less optimal habitat (pasture) may be at greater risk of disease, or that diseased wombats may be competitively excluded from more optimal habitat (vegetated areas). We discuss implications for understanding and managing mange in wombats and cross-applicability to other mange-affected species with environmental transmission.

Spatio-temporal and transmission dynamics of sarcoptic mange in an endangered New World kit fox

Sarcoptic mange poses a serious conservation threat to endangered San Joaquin kit foxes (Vulpes macrotis mutica). After first appearing in Bakersfield, California in spring 2013, mange reduced the kit fox population approximately 50% until the epidemic ended with minimally detectable endemic cases after 2020. Mange is lethal and thus, with such a high force of infection and lack of immunity, it remains unclear why the epidemic did not burn itself out rapidly and how it persisted so long. Here we explored spatio-temporal patterns of the epidemic, analyzed historical movement data, and created a compartment metapopulation model (named "metaseir") to evaluate whether movement of foxes among patches and spatial heterogeneity would reproduce the eight years epidemic with 50% population reduction observed in Bakersfield. Our main findings from metaseir were that: 1) a simple metapopulation model can capture the Bakersfield-like disease epidemic dynamics even when there is no environmental reservoir or external spillover host, 2) the most impactful parameter on persistence and magnitude of the epidemic is the projection, β/αβ (transmission over decay rate of transmission over space), 3) heterogeneity in patch carrying capacities changes the critical value of the projection needed to achieve an epidemic but makes little difference to epidemic persistence time, and 4) the epidemic is relatively insensitive to birth rates and density vs. frequency-dependent transmission. Our model can help guide management and assessment of metapopulation viability of this vulpid subspecies, while the exploratory data analysis and model will also be valuable to understand mange in other, particularly den-occupying, species.

Sarcoptic mange changes bacterial and fungal microbiota of bare-nosed wombats (Vombatus ursinus)

Background

Sarcoptes scabiei is globally distributed and one of the most impactful mammalian ectoparasites. Sarcoptic mange, caused by infection with S. scabiei, causes disruption of the epidermis and its bacterial microbiota, but its effects on host fungal microbiota and on the microbiota of marsupials in general have not been studied. Here, we (i) examine bacterial and fungal microbiota changes associated with mange in wild bare-nosed wombats (BNWs) and (ii) evaluate whether opportunistic pathogens are potentiated by S. scabiei infection in this species.

Methods

Using Amplicon Sequencing of the 16S rRNA and ITS2 rDNA genes, we detected skin microbiota changes of the bare-nosed wombat (Vombatus ursinus). We compared the alpha and beta diversity among healthy, moderate, and severe disease states using ANOVA and PERMANOVA with nesting. Lastly, we identified taxa that differed between disease states using analysis of composition of microbes (ANCOM) testing.

Results

We detected significant changes in the microbial communities and diversity with mange in BNWs. Severely affected BNWs had lower amplicon sequence variant (ASV) richness compared to that of healthy individuals, and the microbial communities were significantly different between disease states with higher relative abundance of potentially pathogenic microbial taxa in mange-affected BNWs including Staphylococcus sciuri, Corynebacterium spp., Brevibacterium spp., Brachybacterium spp., and Pseudogymnascus spp. and Debaryomyces spp.

Conclusion

This study represents the first investigation of microbial changes in association with sarcoptic mange in a marsupial host, as well as the first investigation of fungal microbial changes on the skin of any host suffering from sarcoptic mange. Our results are broadly consistent with bacterial microbiota changes observed in humans, pigs, canids, and Iberian ibex, suggesting the epidermal microbial impacts of mange may be generalisable across host species. We recommend that future studies investigating skin microbiota changes include both bacterial and fungal data to gain a more complete picture of the effects of sarcoptic mange.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05452-y.

Heavy metal wombats? Metal exposure pathways to bare-nosed wombats (Vombatus ursinus) living on remediated tin mine tailings

Rehabilitation of disused mine sites through stabilisation and botanical restoration is ecologically important, but metal transfer pathways to colonising wildlife are often less understood and have never been studied in marsupials. The rehabilitated Royal George tin mine tailings (Tasmania, Australia) and colonisation by bare-nosed wombats (Vombatus ursinus) represented an opportunity to examine potential metal transfer from mine tailings to an herbivorous marsupial. The aim of this study was to examine metal transfer pathways from the mine tailings to wombats, and to determine if wombats are at risk from metal exposure. Concentrations of metals were measured in the tailings substrate, surface water and vegetation, as well as fur samples from a resident wombat, and non-resident (control) wombats. The mineralogy of the tailings is dominated by quartz, muscovite, feldspars, topaz, kaolinite and calcite. Concentrations of several metals were high (exceeding varying health standards) in the tailings (As, Cu, Hg, Pb, Ni, Zn), water (As, Cd, Cu, Zn) and vegetation (As, Cd, Cu, Pb, Mn, Zn). Relative to non-resident wombats, elevated levels of As, Cd, Cu, Pb and Sn were measured in the fur of a resident wombat. Based on modelling of the exposure pathways, consumption of plant material is the most likely metal transfer pathway for As, Cu and Pb, although the risks from ingestion of tailings to this fossorial marsupial should not be discounted. This study is the first to investigate metal exposure pathways to marsupials using rehabilitated mine tailings. Further research is needed to accurately quantify ecological risks and toxicity for wombats and other marsupials native to mining landscapes.

Signs of Rumpwear in the Common Ringtail Possum, Pseudocheirus peregrinus

We report the physical characteristics of rumpwear in the Australian common ringtail possum, Pseudocheirus peregrinus. Rumpwear presents as varying grades of hair breakage and dermatitis on the lumbosacral region. This condition has been reported in Trichosurus spp. (brushtail possums) previously, but never in P. peregrinus. The etiology remains poorly understood.

Pathophysiological and Pharmaceutical Considerations for Enhancing the Control of Sarcoptes scabiei in Wombats Through Improved Transdermal Drug Delivery

Sarcoptic scabiei is an invasive parasitic mite that negatively impacts wombats, causing sarcoptic mange disease, characterized by alopecia, intense pruritus, hyperkeratosis, and eventual mortality. Evidence suggests that wombats may be unable to recovery from infection without the assistance of treatments. Transdermal drug delivery is considered the most ideal route of administration for in situ treatment in free-ranging wombats, as it is non-invasive and avoids the need to capture affected individuals. Although there are effective antiparasitic drugs available, an essential challenge is adequate administration of drugs and sufficient drug retention and absorption when delivered. This review will describe the implications of sarcoptic mange on the physiology of wombats as well as discuss the most widely used antiparasitic drugs to treat S. scabiei (ivermectin, moxidectin, and fluralaner). The prospects for improved absorption of these drugs will be addressed in the context of pathophysiological and pharmaceutical considerations influencing transdermal drug delivery in wombats with sarcoptic mange.

Occurrence of sarcoptic mange in free-ranging vicuñas (Vicugna vicugna) of the Andean high plateau region of Argentina

Free-ranging vicuñas (Vicugna vicugna) are handled in some areas of the Andean high plateau region following an ancestral practice known as chaku, which consists in their transient capture and shearing of their fiber for commercialization. In this study, 807 vicuñas captured during 12 chaku events that took place in 2019 in the province of Jujuy, Argentina, were examined for typical mange skin lesions. Twenty-eight of the examined vicuñas presented alopecia with erythema, exudation, hyperkeratosis, and/or bleeding scarred lesions, mostly in the chest, rear and front legs, and inguinal zone. Most of the cases (82%) appeared in Laguna Cucho at 4900 masl, where 23% of the animals presented these skin reactions. Microscopic evaluation of skin scrapings revealed the presence of a great number of 0.1- to 0.4-mm-long mites of different life cycle stages, morphologically compatible with the species Sarcoptes scabiei. This etiological agent was confirmed by PCR amplification and sequencing of a cox-1 species-specific segment. Histopathological examination of skin biopsies showed extensive infiltration of the dermis with lymphocytes, neutrophils and eosinophils, hyperplasia at different stages, epidermis degeneration, and hyperkeratosis. This is the first characterization of sarcoptic mange in free-ranging vicuñas by clinical examination, mite morphology, histopathological studies, and molecular confirmation in the region. Mange hampers the welfare of vicuñas and the economy of the local communities that organize chaku events since infested vicuñas cannot be sheared. Its long-term effects are unknown but it might affect the fitness and survival of this iconic South American camelid.

Sustaining Transmission in Different Host Species: The Emblematic Case of Sarcoptes scabiei

Some pathogens sustain transmission in multiple different host species, but how this epidemiologically important feat is achieved remains enigmatic. Sarcoptes scabiei is among the most host generalist and successful of mammalian parasites. We synthesize pathogen and host traits that mediate sustained transmission and present cases illustrating three transmission mechanisms (direct, indirect, and combined). The pathogen traits that explain the success of S. scabiei include immune response modulation, on-host movement capacity, off-host seeking behaviors, and environmental persistence. Sociality and host density appear to be key for hosts in which direct transmission dominates, whereas in solitary hosts, the use of shared environments is important for indirect transmission. In social den-using species, combined direct and indirect transmission appears likely. Empirical research rarely considers the mechanisms enabling S. scabiei to become endemic in host species—more often focusing on outbreaks. Our review may illuminate parasites’ adaptation strategies to sustain transmission through varied mechanisms across host species.

Environmental suitability of bare-nosed wombat burrows for Sarcoptes scabiei

Some of the most important pathogens affecting wildlife are transmitted indirectly via the environment. Yet the environmental stages of pathogens are often poorly understood, relative to infection in the host, making this an important research frontier. Sarcoptic mange is a globally widespread disease caused by the parasitic mite Sarcoptes scabiei. The bare-nosed wombat (Vombatus ursinus) is particularly susceptible, and their solitary nature and overlapping use of burrows strongly indicate the importance of environmental transmission. However, due to the challenge of accessing and monitoring within wombat burrows, there has been limited research into their suitability for off-host mite survival and environmental transmission (i.e., to serve as a fomite). We created a model using published laboratory data to predict mite survival times based on temperature and humidity. We then implemented innovative technologies (ground-penetrating radar and a tele-operated robotic vehicle) to map and access wombat burrows to record temperature and relative humidity. We found that the stable conditions within burrows were conducive for off-host survival of S. scabiei, particularly in winter (estimated mite survival of 16.41 ± 0.34 days) and less so in warmer and drier months (summer estimated survival of 5.96 ± 0.37 days). We also compared two areas with higher and lower average mange prevalence in wombats (13.35% and 4.65%, respectively), finding estimated mite survival was slightly higher in the low prevalence area (10.10 and 12.12 days, respectively), contrary to our expectations, suggesting other factors are also important for population prevalence. Our study is the first to demonstrate the suitability of the bare-nosed wombat burrow for off-host mite survival and environmental transmission. Our findings have implications for understanding observed patterns of mange, disease dynamics and disease management for not only bare-nosed wombats, but also other burrow or den-obligate species exposed to S. scabiei via environmental transmission.

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Wombat burrows are a source of environmental transmission of Sarcoptes scabiei.

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We used ground-penetrating radar and a robotic vehicle to measure burrow conditions.

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We estimate S. scabiei can survive 5.96–16.41 days within burrows depending on season.

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Seasonal variation in environmental survival may influence disease dynamics in wombats.

WomBot: an exploratory robot for monitoring wombat burrows

Abstract

In this study we evaluate the design and efficacy of Wombot, an exploratory robot used to study environmental conditions within wombat burrows. Our purpose-built robot traverses through the difficult terrain present in wombat burrows whilst facilitating placement and retrieval of environmental data loggers. Our preliminary results suggest that the environmental conditions present within the burrows would result in a long mite survival time which shows significant risk for spreading infestations throughout a wombat population.

Article Highlights

Sarcoptic mange: An emerging panzootic in wildlife

Sarcoptic mange, a skin infestation caused by the mite Sarcoptes scabiei, is an emerging disease for some species of wildlife, potentially jeopardizing their welfare and conservation. Sarcoptes scabiei has a near-global distribution facilitated by its forms of transmission and use of a large diversity of host species (many of those with broad geographic distribution). In this review, we synthesize the current knowledge concerning the geographic and host taxonomic distribution of mange in wildlife, the epidemiological connections between species, and the potential threat of sarcoptic mange for wildlife conservation. Recent sarcoptic mange outbreaks in wildlife appear to demonstrate ongoing geographic spread, increase in the number of hosts and increased virulence. Sarcoptic mange has been reported in at least 12 orders, 39 families and 148 species of domestic and wild mammals, making it one of the most generalist ectoparasites of mammals. Taxonomically, the orders with most species found infested so far include Perissodactyla (67% species from the entire order), Artiodactyla (47%), and Diprotodontia (67% from this order). This suggests that new species from these mammal orders are likely to suffer cross-species transmission and be reported positive to sarcoptic mange as surveillance improves. We propose a new agenda for the study of sarcoptic mange in wildlife, including the study of the global phylogeography of S. scabiei, linkages between ecological host traits and sarcoptic mange susceptibility, immunology of individuals and species, development of control strategies in wildlife outbreaks and the effects of global environmental change in the sarcoptic mange system. The ongoing transmission globally and sustained spread among areas and wildlife species make sarcoptic mange an emerging panzootic in wildlife. A better understanding of sarcoptic mange could illuminate the aspects of ecological and evolutionary drivers in cross-species transmission for many emerging diseases.

Non-Invasive Molecular Survey of Sarcoptic Mange in Wildlife: Diagnostic Performance in Wolf Faecal Samples Evaluated by Multi-Event Capture-Recapture Models

Sarcoptic mange is globally enzootic, and non-invasive methods with high diagnostic specificity for its surveillance in wildlife are lacking. We describe the molecular detection of Sarcoptes scabiei in non-invasively collected faecal samples, targeting the 16S rDNA gene. We applied this method to 843 Iberian wolf Canis lupus signatus faecal samples collected in north-western Portugal (2006-2018). We further integrated this with serological data (61 samples from wolf and 20 from red fox Vulpes vulpes, 1997-2019) in multi-event capture-recapture models. The mean predicted prevalence by the molecular analysis of wolf faecal samples from 2006-2018 was 7.2% (CI₉₅ 5.0-9.4%; range: 2.6-11.7%), highest in 2009. The mean predicted seroprevalence in wolves was 24.5% (CI₉₅ 18.5-30.6%; range: 13.0-55.0%), peaking in 2006-2009. Multi-event capture-recapture models estimated 100% diagnostic specificity and moderate diagnostic sensitivity (30.0%, CI₉₅ 14.0-53.0%) for the molecular method. Mange-infected individually identified wolves showed a tendency for higher mortality versus uninfected wolves (ΔMortality 0.150, CI₉₅ -0.165-0.458). Long-term serology data highlights the endemicity of sarcoptic mange in wild canids but uncovers multi-year epidemics. This study developed and evaluated a novel method for surveying sarcoptic mange in wildlife populations by the molecular detection of S. scabiei in faecal samples, which stands out for its high specificity and non-invasive character.

Sarcoptic mange severity is associated with reduced genomic variation and evidence of selection in Yellowstone National Park wolves (Canis lupus)

Population genetic theory posits that molecular variation buffers against disease risk. Although this "monoculture effect" is well supported in agricultural settings, its applicability to wildlife populations remains in question. In the present study, we examined the genomics underlying individual-level disease severity and population-level consequences of sarcoptic mange infection in a wild population of canids. Using gray wolves (Canis lupus) reintroduced to Yellowstone National Park (YNP) as our focal system, we leveraged 25 years of observational data and biobanked blood and tissue to genotype 76,859 loci in over 400 wolves. At the individual level, we reported an inverse relationship between host genomic variation and infection severity. We additionally identified 410 loci significantly associated with mange severity, with annotations related to inflammation, immunity, and skin barrier integrity and disorders. We contextualized results within environmental, demographic, and behavioral variables, and confirmed that genetic variation was predictive of infection severity. At the population level, we reported decreased genome-wide variation since the initial gray wolf reintroduction event and identified evidence of selection acting against alleles associated with mange infection severity. We concluded that genomic variation plays an important role in disease severity in YNP wolves. This role scales from individual to population levels, and includes patterns of genome-wide variation in support of the monoculture effect and specific loci associated with the complex mange phenotype. Results yielded system-specific insights, while also highlighting the relevance of genomic analyses to wildlife disease ecology, evolution, and conservation.

Fluralaner as a novel treatment for sarcoptic mange in the bare-nosed wombat (Vombatus ursinus): safety, pharmacokinetics, efficacy and practicable use

Background

Sarcoptic mange causes significant animal welfare and occasional conservation concerns for bare-nosed wombats (Vombatus ursinus) throughout their range. To date, in situ chemotherapeutic interventions have involved macrocytic lactones, but their short duration of action and need for frequent re-administration has limited treatment success. Fluralaner (Bravecto®; MSD Animal Health), a novel isoxazoline class ectoparasiticide, has several advantageous properties that may overcome such limitations.

Methods

Fluralaner was administered topically at 25 mg/kg (n = 5) and 85 mg/kg (n = 2) to healthy captive bare-nosed wombats. Safety was assessed over 12 weeks by clinical observation and monitoring of haematological and biochemical parameters. Fluralaner plasma pharmacokinetics were quantified using ultra-performance liquid chromatography and tandem mass spectrometry. Efficacy was evaluated through clinical assessment of response to treatment, including mange and body condition scoring, for 15 weeks after topical administration of 25 mg/kg fluralaner to sarcoptic mange-affected wild bare-nosed wombats (n = 3). Duration of action was determined through analysis of pharmacokinetic parameters and visual inspection of study subjects for ticks during the monitoring period. Methods for diluting fluralaner to enable ‘pour-on’ application were compared, and an economic and treatment effort analysis of fluralaner relative to moxidectin was undertaken.

Results

No deleterious health impacts were detected following fluralaner administration. Fluralaner was absorbed and remained quantifiable in plasma throughout the monitoring period. For the 25 mg/kg and 85 mg/kg treatment groups, the respective means for maximum recorded plasma concentrations (C_max) were 6.2 and 16.4 ng/ml; for maximum recorded times to C_max, 3.0 and 37.5 days; and for plasma elimination half-lives, 40.1 and 166.5 days. Clinical resolution of sarcoptic mange was observed in all study animals within 3–4 weeks of treatment, and all wombats remained tick-free for 15 weeks. A suitable product for diluting fluralaner into a ‘pour-on’ was found. Treatment costs were competitive, and predicted treatment effort was substantially lower relative to moxidectin.

Conclusions

Fluralaner appears to be a safe and efficacious treatment for sarcoptic mange in the bare-nosed wombat, with a single dose lasting over 1–3 months. It has economic and treatment-effort-related advantages over moxidectin, the most commonly used alternative. We recommend a dose of 25 mg/kg fluralaner and, based on the conservative assumption that at least 50% of a dose makes dermal contact, Bravecto Spot-On for Large Dogs as the most appropriate formulation for adult bare-nosed wombats.

Graphical abstract

Host-Parasite Interaction in Sarcoptes scabiei Infestation in Porcine Model with a Preliminary Note on Its Genetic Lineage from India

Simple Summary

Scabies or mange caused by Sarcoptess cabiei is the latest addition of WHO’s list oftropical neglected diseases. It causes severe itching to the host. It has a wide host range including humans, farm animals, companion animals, and wild animals. It is anemerging/re-emerging disease with high prevalence in underdeveloped and developing countries. The disease has zoonotic importance and is of significant public health concern as cross-transmission or species jumping is very common. To date, fifteen Sarcoptes varieties have been reported as per host origin. Differential diagnosis at variety level is very crucial for epidemiological study and scratching future eradication program of the disease. As morphotaxonomy fails to differentiate varieties, use of molecular markers is crucial. Moreover, it is very important to understand the host-parasite interaction at the systemic level for a better understanding on the pathogenicity of the disease. Here, we report the genetic characterization of S. scabiei from India and host-parasite interaction in a porcine model.

Abstract

The burrowing mite Sarcoptes scabiei causes scabies in humans or mange in animals. It infests a wide range of mammalian species including livestock, companion animals, wild animals, and humans. Differential diagnosis of Sarcoptes varieties is key for epidemiological studies and for formulation of an eradication program. Host-parasite interaction at the systemic level is very important to understand the pathogenicity of the mite. This communication deals with the preliminary report on the genetic characterization of S. scabiei from India. Moreover, the effect of S. scabiei infestation on host physiology with special emphasis on serum biochemical parameters, lipid profile, oxidant/antioxidant balance, stress parameters, and immune responses were evaluated in a porcine model. Cytochrome C oxidase 1 and voltage-sensitive sodium channel based phylogenetic study could distinguish human and animals isolates but could not distinguish host or geographical specific isolates belonging to animal origin. An absence of host-specific cluster among animal isolates argues against the hypothesis of delineating S. scabiei as per host origin. Elevated levels of markers of liver function such as albumin, AST, ALT, ALP, and LDH in infested animals indicated impaired liver function in infested animals. S. scabiei infestation induced atherogenic dyslipidemia indicated by elevated levels of total cholesterol, low-density lipoprotein cholesterol and triglycerides, and a decreased level of high-density lipoprotein cholesterol. Oxidative stress in infested animals was indicated by a high level of nitric oxide and serum MDA as oxidative stress markers and low antioxidant capacity. S. scabiei triggered stress response and elevated levels of serum cortisol and heat shock proteins were recorded in infested animals. S. scabiei infestation increased the serum concentration of immunoglobulins and was associated with up-regulation of IL-2, IFN-γ, IL-1β, and IL-4 indicating both Th1 and Th2 response. The results of the study will be helpful for a better understanding of host-parasite interaction at the systemic level in crusted scabies in pigs.

Individual stress responses to Sarcoptes scabiei infestation in Iberian ibex, Capra pyrenaica

In this study we have monitored the stress of Iberian ibex at individual level within the course of an experimental infection with Sarcoptes scabiei mites. For this purpose we have measured faecal 11-ketoetiocholanolone (11-k) using high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS). We used linear mixed models to explore the effects of host sex and age, clinic (mange status) and time (number of days post-infection) on the concentration of faecal 11-k. The most parsimonious model included clinic, time and host age, which explained 76.6% of the variance of the response variable. Moreover, the concentration of faecal 11-k varied greatly between individuals. Our results evidence the stressor nature of the disease and highlight the negative effects on hosts due to cortisol release and activity.

A review of sarcoptic mange in North American wildlife

The "itch mite" or "mange mite", Sarcoptes scabiei, causes scabies in humans and sarcoptic mange in domestic and free-ranging animals. This mite has a wide host range due to its ability to adapt to new hosts and has been spread across the globe presumably through human expansion. While disease caused by S. scabiei has been very well-studied in humans and domestic animals, there are still numerous gaps in our understanding of this pathogen in free-ranging wildlife. The literature on sarcoptic mange in North American wildlife is particularly limited, which may be due to the relatively limited number of clinically-affected species and lack of severe population impacts seen in other continents. This review article provides a summary of the current knowledge of mange in wildlife, with a focus on the most common clinically-affected species in North America including red foxes (Vulpes vulpes), gray wolves (Canis lupus), coyotes (Canis latrans), and American black bears (Ursus americanus).

The treatment of sarcoptic mange in wildlife: a systematic review

BACKGROUND

Sarcoptic mange, caused by the Sarcoptes scabiei mite, is an infectious disease of wildlife, domestic animals and humans with international importance. Whilst a variety of treatment and control methods have been investigated in wildlife, the literature is fragmented and lacking consensus. The primary objectives of this review were to synthesise the diverse literature published on the treatment of sarcoptic mange in wildlife from around the world, and to identify the qualities of successful treatment strategies in both captive and free-roaming wildlife.

METHODS

A systematic search of the electronic databases CAB Direct, PubMed, Scopus, Web of Science, EMBASE and Discovery was undertaken. Data pertaining to study design, country, year, species, study size, mange severity, treatment protocol and outcomes were extracted from eligible studies and placed in a table. Following data extraction, a decision tree was used to identify studies suitable for further analysis based on the effectiveness of their treatment protocol, whether they were conducted on captive or non-captive wildlife, and the quality of their post-treatment monitoring period.

RESULTS

Twenty-eight studies met our initial inclusion criteria for data collection. Of these studies, 15 were selected for further analysis following application of the decision tree. This comprised of 9 studies on captive wildlife, 5 studies on free-living wildlife and 1 study involving both captive and free-living wildlife. Ivermectin delivered multiple times via subcutaneous injection at a dose between 200-400 µg/kg was found to be the most common and successfully used treatment, although long-term data on post-release survival and re-infection rates was elusive.

CONCLUSIONS

To our knowledge, this review is the first to demonstrate that multiple therapeutic protocols exist for the treatment of sarcoptic mange in wildlife. However, several contemporary treatment options are yet to be formally reported in wildlife, such as the use of isoxazoline chemicals as a one-off treatment. There is also a strong indication for more randomised controlled trials, as well as improved methods of post-treatment monitoring. Advancing this field of knowledge is expected to aid veterinarians, wildlife workers and policy makers with the design and implementation of effective treatment and management strategies for the conservation of wildlife affected by sarcoptic mange.

A model for the treatment of environmentally transmitted sarcoptic mange in bare-nosed wombats (Vombatus ursinus)

Some of the most important wildlife diseases involve environmental transmission, with disease control attempted via treatments that induce temporary pathogen resistance among hosts. However, theoretical explanations of such circumstances remain few. A mathematical model is proposed and investigated to analyse the dynamics and treatment of environmentally transmitted sarcoptic mange in a population of bare-nosed wombats. The wombat population is structured into four classes representing stages of infection, in a model that consists of five non-linear differential equations including the unattached mite population. It is shown that four different epidemiological outcomes are possible. These are: (1) extinction of wombats (and mites); (2) mite-free wombat populations; (3) endemic wombats and mites coexisting, with the wombats' population reduced below the environmental carrying capacity; and (4) a stable limit cycle (sustained oscillating populations) with wombat population far below carrying capacity. Empirical evidence exists for the first two of these outcomes, with the third highly likely to occur in nature, and the fourth plausible at least until wombat populations succumb to Allee effects. These potential outcomes are examined to inform treatment programs for wombat populations. Through this theoretical exploration of a relatively well understood empirical system, this study supports general learning across environmentally transmitted wildlife pathogens, increasing understanding of how pathogen dynamics may cause crashes in some populations and not others.

International meeting on sarcoptic mange in wildlife, June 2018, Blacksburg, Virginia, USA

Sarcoptic mange is a globally distributed disease caused by the burrowing mite Sarcoptes scabiei, which also causes scabies in humans. A wide and increasing number of wild mammal species are reported to be susceptible to mange; however, the impacts of the disease in wildlife populations, mechanisms involved in its eco-epidemiological dynamics, and risks to public and ecosystem health are still unclear. Major gaps exist concerning S. scabiei host specificity and the mechanisms involved in the different presentations of the disease, which change between individuals and species. Immunological responses to the mite may have a relevant role explaining these different susceptibilities, as these affect the clinical signs, and consequently, the severity of the disease. Recently, some studies have suggested sarcoptic mange as an emerging threat for wildlife, based on several outbreaks with increased severity, geographical expansions, and novel wild hosts affected. Disease ecology experts convened for the “International Meeting on Sarcoptic Mange in Wildlife” on 4–5 June 2018, hosted by the Department of Fish and Wildlife Conservation at Virginia Tech in Blacksburg, Virginia, USA. The meeting had a structure of (i) pre-workshop review; (ii) presentation and discussions; and (iii) identification of priority research questions to understand sarcoptic mange in wildlife. The workgroup concluded that research priorities should be on determining the variation in modes of transmission for S. scabiei in wildlife, factors associated with the variation of disease severity among species, and long-terms effects of the mange in wildlife populations. In this note we summarize the main discussions and research gaps identified by the experts.