Sex-biased severity of sarcoptic mange at the same biological cost in a sexually dimorphic ungulate

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.

Spatial and temporal patterns of sarcoptic mange in wombats using the citizen science tool, WomSAT

There is currently limited information regarding the levels of infection and distribution of sarcoptic mange in the wombat population throughout Australia. We analyzed cases of sarcoptic mange in bare-nosed wombats reported into WomSAT, a website and mobile phone application where citizen scientists can upload sightings of wombats, burrows, and sarcoptic mange status. We used Maxent software to predict locations and the environmental factors associated with sarcoptic mange occurrence in bare-nosed wombats. A total of 1379 sarcoptic mange-infected and 3043 non-sarcoptic mange-infected wombats were reported by 674 and 841 citizen scientists, respectively. Of all the wombats reported to WomSAT from 2015 to 2019, 31.2% were infected with sarcoptic mange. Sarcoptic mange in bare-nosed wombats was reported in 502 suburbs across four states. New South Wales had the highest number of sarcoptic mange cases reported to WomSAT. There was no statistically significant seasonal variation of sarcoptic mange levels in bare-nosed wombats. The model showed that Euclidean distance to urban areas was the highest contributing factor for sarcoptic mange occurrence. As distance to urban areas decreased, the suitability for sarcoptic mange increased. Annual precipitation was the next contributing factor in the model, with higher rainfall of 400-700 mm correlating to an increase in sarcoptic mange occurrence. As the data collected to date have provided the largest-scale contemporary distribution of sarcoptic mange in wombats, data should continue to be collected by citizen scientists as it is an easy and low-cost method of collecting data over large areas. We suggest targeting the identified hotspot areas and more site-specific studies for studying and mitigating sarcoptic mange in bare-nosed wombats.

Epidemiology of Anaplasma marginale and Anaplasma centrale infections in African buffalo (Syncerus caffer) from Kruger National Park, South Africa

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Diseases of Iberian ibex (Capra pyrenaica)

Iberian ibex (Capra pyrenaica) is an ecologically and economically relevant medium-sized emblematic mountain ungulate. Diseases participate in the population dynamics of the species as a regulating agent, but can also threaten the conservation and viability of vulnerable population units. Moreover, Iberian ibex can also be a carrier or even a reservoir of pathogens shared with domestic animals and/or humans, being therefore a concern for livestock and public health. The objective of this review is to compile the currently available knowledge on (1) diseases of Iberian ibex, presented according to their relevance on the health and demography of free-ranging populations; (2) diseases subjected to heath surveillance plans; (3) other diseases reported in the species; and (4) diseases with particular relevance in captive Iberian ibex populations. The systematic review of all the information on diseases affecting the species unveils unpublished reports, scientific communications in meetings, and scientific articles, allowing the first comprehensive compilation of Iberian ibex diseases. This review identifies the gaps in knowledge regarding pathogenesis, immune response, diagnostic methods, treatment, and management of diseases in Iberian ibex, providing a base for future research. Moreover, this challenges wildlife and livestock disease and wildlife population managers to assess the priorities and policies currently implemented in Iberian ibex health surveillance and monitoring and disease management.

Co-infection patterns in the ectoparasitic community affecting the Iberian ibex Capra pyrenaica

BACKGROUND

Sarcoptic mange is one of the main parasitic diseases affecting the Iberian ibex Capra pyrenaica. Scabietic animals suffer a decline in body condition and reproductive fitness and in severe cases may die. Although several previous studies of the pathology of this disease and the physiological changes it produces in ibex have been carried out in recent years, our knowledge of the relationship between Sarcoptes scabiei and other ectoparasites of this host is still limited.

METHODS

We analysed 430 Iberian ibex skin samples. Ectoparasites were removed, counted and identified. Mite (S. scabiei) numbers were obtained after digesting the skin samples in a 5% KOH solution. We modelled mite numbers in terms of host sex and age, site, year, season and the presence of other ectoparasites such as ticks and lice using generalized linear mixed models (GLMMs) and ectoparasite co-occurrence patterns using two different models: the probabilistic model species co-occurrence and the generalized linear latent variable model (GLLVM).

RESULTS

The ectoparasite community was mainly composed of S. scabiei, six ticks (Haemaphysalis sulcata, Haemaphysalis punctata, Rhipicephalus bursa, Rhipicephalus turanicus, Dermacentor marginatus and Ixodes ricinus) and two lice (Bovicola crassipes and Linognathus stenopsis). Adult male ibex harboured more mites than females. Mite numbers varied greatly spatially and seasonally and increased with the presence of other parasites. Some positive co-occurrence relationships between pairs of different ectoparasites were observed, particularly between ticks. The presence of S. scabiei negatively affected lice and H. sulcata numbers.

CONCLUSIONS

Sarcoptic mange has spread above all in ibex populations in and around the Mediterranean Basin, where it is now found in almost a third of its host's range. Mite numbers varied seasonally and spatially and were higher in male hosts. The presence of S. scabiei had a negative effect on lice numbers but favoured the presence of ticks.

Low impact of tuberculosis severity on wild boar body condition

Body condition (BC), is a measure to assess the health status of domestic and wild animals. When food resources are abundant, a decrease in BC may indicate an increase in the energetic expenditure due to the effects of growth, reproduction, or disease. BC impoverishment is one of the most common clinical effects of diseases progressing chronically, such as animal tuberculosis (TB) caused by bacteria belonging to the Mycobacterium tuberculosis complex. The Eurasian wild boar (Sus scrofa) is the main wild TB reservoir in the Mediterranean basin. The specific aims of this work were to assess the relationship between sex, age and TB severity altogether on the BC of wild boar. For this purpose, we used the kidney fat index (KFI), to assess the impact of TB progression on the BC of 1372 hunter-harvested free-ranging wild boar in seven populations in southern Spain. Surprisingly, TB had only slight effects on wild boar BC and individuals exhibiting severe TB showed greater BC than TB-free individuals. The age (adults had greater BC than juveniles) and sex (females had greater BC than males) were the main BC determinants in wild boar. Sampling population and season explained more BC variability than individual factors, suggesting that other external factors might play an important role in the BC, and probably on the impact of the disease on this wild reservoir. The low impact of TB on wild boar BC suggests that individuals with severe TB and good BC represent potential long-term super-shedders of this pathogen.

From trees to fleas: masting indirectly affects flea abundance on a rodent host

Mast seeding causes strong fluctuations in populations of forest animals. Thus, this phenomenon can be used as a natural experiment to examine how variation in host abundance affects parasite loads. We investigated fleas infesting yellow-necked mice in beech forest after two mast and two non-mast years. We tested two mutually exclusive scenarios: (1) as predicted by classical models of density-dependent transmission, an increase in host density will cause an increase in ectoparasite abundance (defined as the number of parasites per host), vs. (2) an increase in host density will cause a decline in flea abundance ("dilution", which is thought to occur when parasite population growth is slower than that of the host). In addition, we assessed whether masting alters the relationship between host traits (sex and body mass) and flea abundance. We found a hump-shaped relationship between host and flea abundance. Thus, the most basic predictions are too simple to describe ectoparasite dynamics in this system. In addition, masting modified seasonal dynamics of flea abundance, but did not affect the relationship between host traits and flea abundance (individuals with the highest body mass hosted the most fleas; after controlling for body mass, parasite abundance did not vary between sexes). Our results demonstrate that pulses of tree reproduction can indirectly, through changes in host densities, drive patterns of ectoparasite infestation. This article is protected by copyright. All rights reserved.

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.

Immune challenge of mating effort: steroid hormone profile, dark ventral patch and parasite burden in relation to intrasexual competition in male Iberian red deer

Testosterone secretion may regulate the reproductive effort and the development of sexual traits, but it may also involve costs at the immunological and metabolic levels. However, the evidence for this trade-off in wild populations is scarce. Cortisol also plays an important role in mediating the reproductive and immune functions. In this study, we analyzed whether the endoparasite burden relates to hormonal levels (fecal testosterone and cortisol metabolites) and/or morphological sexual traits (size of the dark ventral patch, a trait that indicates reproductive effort in males) in male Iberian red deer. For this purpose, we sampled male red deer harvested during hunting actions in 2 types of populations in south western Spain that differed in structure, affecting the level of male-male competition for mates. We used coprological analyses to estimate the parasite burden mainly of gastrointestinal and bronchopulmonary nematodes and of protozoa, and assessed testosterone and cortisol metabolite levels from fecal pellets. We found a positive relationship of host parasitation with both testosterone levels and the size of the dark ventral patch, but these relationships depended on the intensity of male-male competition in the population, being only found under the high-competition scenario. These results are discussed under the hypothesis of the testosterone immunocompetence handicap, suggesting a cost at the immunological level, and, therefore, higher susceptibility to parasite infection in males that make a greater reproductive effort. However, this effect seems to be modulated by the social environment (male-male competition) that might lead to different optima in testosterone production and sexual trait development.

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.

How sensitive and specific is the visual diagnosis of sarcoptic mange in free-ranging Iberian ibexes?

Background

Sarcoptic mange is a broadly distributed parasitic disease caused by Sarcoptes scabiei that affects wild mammals from all over the world, including the Iberian ibex (Capra pyrenaica). Selective culling of the scabietic individuals is the main management measure for disease control in Iberian ibex populations. Although visual identification of mange-compatible lesions is the reference method to decide the target individual, both false negative and positive cases are common in the wild. The aim of this work is to determine the sensitivity (SE), and the specificity (SP) of selective culling after evaluating 403 ibexes hunted in the Sierra Nevada Nature Space for sarcoptic mange control between 2002 and 2015.

Methods

A combination of skin scrapings and potassium hidroxide (KOH) skin digestion was used for sarcoptic mange diagnosis. Generalized linear models (GLM) were used to assess the effects of sex, age (juveniles and adults) and period of the year (wet and dry periods) on the SE and SP of the visual diagnosis method.

Results

The SE obtained for the visual determination of scabietic ibexes was 87.14%, whereas the SP was 60.71%. According to our model selection, SE of the visual diagnosis was explained by the additive effects of age and the period of the year. In fact, SE was lower in juveniles (64.76%) than in adults (94.26%) and during the dry period (73.44%) as compared to the wet period (92.09%). On the other hand, SP was best explained by the GLM including the additive effects of sex and the period of the year. The visual diagnosis of sarcoptic mange resulted less specific in females (22.73%) than in males (74.19%) and during the wet (55.22%) than in the dry period (82.35%).

Conclusions

Maximizing SE and SP is essential to achieving a high rate of removal of affected individuals from the environment without eliminating potentially resistant individuals. Selective culling must be conservative during the wet period and with females due to the lower SP. Conversely, visual diagnosis of scabietic juveniles and during the dry period has to be improved, due to the lower SE.

Characterizing the growth of Sarcoptes scabiei infrapopulations

During the course of parasitic disease infestations, parasite population sizes change at both individual host (infrapopulation) and host population (metapopulation) levels. However, most studies only report epidemiological values for specific locations and times. In this study we analysed the dynamics of several Sarcoptes scabiei infrapopulations from experimentally infested Iberian ibex, Capra pyrenaica. We obtained mite counts by digesting small skin biopsies, which we compared with indices obtained from histopathological analyses performed on adjacent skin biopsies. We obtained the finite growth rate and the daily growth rate for the mite infrapopulations: mean ± SE = 11.53 ± 10.17 and 0.10 ± 0.08 mites/day, respectively. Mite counts derived from skin sample digestion did not correlate with the histological mite indices obtained from adjacent skin biopsies. At a metapopulational level, both indices of mite abundance were modelled using GLMMs and the factors influencing their variation are analysed and discussed. Our results suggest that mites are not distributed uniformly over the whole area of the skin lesion. Therefore, direct diagnoses of mange and mite counts could be inaccurate if only small skin samples are used.

Sarcoptes scabiei alters follicular dynamics in female Iberian ibex through a reduction in body weight

Normal development of the ovarian cycle is a key factor in ensuring female reproductive success. Sarcoptes scabiei has been shown to induce changes in host physiology, although the effects of this mite on the female reproductive cycle are still unknown. In an attempt to clarify this issue, the number of ovarian structures (primary follicles, secondary follicles, Graaf follicles, corpus luteum and corpus albicans) in female Iberian ibex (Capra pyrenaica) affected by sarcoptic mange was explored by histological analysis of samples taken from 102 females selectively harvested in the Sierra Nevada Natural Space, southern Spain. The effect of mange status, body weight (corrected for age), age and year of sampling on the number of ovarian structures was assessed using generalized linear models. Our results provide evidence that sarcoptic mange alters follicular dynamics through a reduction in host body weight, whose main consequences are noted in follicular maturation and ovulatory capacity.

Evaluation of oxidant/antioxidant balance in Iberian ibex (Capra pyrenaica) experimentally infested with Sarcoptes scabiei

Oxidative stress (OS) is an imbalance between radical-generating and radical scavenging activity, resulting in oxidation products and tissue damage. Although some studies have been done in other species, there is a lack of information about the oxidative/antioxidant status in the Iberian ibex (Capra pyrenaica) affected by sarcoptic mange. To clarify this fact, albumin, catalase (CAT), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), paraoxonase-1 (PON-1), glutathione reductase (GR), reduced glutathione (GSH): oxidized glutathione (GSSG) ratio, thiobarbituric acid reactive substances (TBARS) and total oxidant status (TOS) concentrations were measured in peripheral blood of ibexes experimentally infested with Sarcoptes scabiei (n=25), as well as in the healthy control group (n=14). During the course of the experiment, the infected ibexes were visually assigned to four categories according to the percentage of skin surface affected by mites. In the infested ibexes, the levels of albumin, PON-1, CAT, SOD, GSH-Px and GSH:GSSG ratio showed a significant (p<0.01) decrease with disease progression. With respect to the control group, this decrease was significantly (p<0.001) lower in the more severe clinical stages. No significant changes were observed in GR activity during disease or with respect to the control group. Conversely, the concentrations of TOS and TBARS increased with lesion severity, and with respect to the control group, this increase was significant (p<0.01) in the more advanced stages of the infection. Additionally, to explore the possible effects of sex, age, haplotype, mange status, and days post infection (dpi) on each of the OS biomarkers, generalized additive mixed models were applied. According to our results, the mange status and dpi explained the highest percentages in the observed changes in the biomarkers analyzed, whereas the haplotype only influenced the observed variability of albumin and TOS. The contribution of sex and age was not significant in any of the OS biomarkers. From the present study, it may be concluded that sarcoptic mange infestation increases OS and decreases antioxidant status in ibex. This imbalance may contribute to the pathogenesis of this disease.

Evaluation of three enzyme-linked immunosorbent assays for sarcoptic mange diagnosis and assessment in the Iberian ibex, Capra pyrenaica

BACKGROUND

Sarcoptic mange is a contagious skin disease caused by the mite Sarcoptes scabiei, affecting different mammalian species worldwide including the Iberian ibex (Capra pyrenaica), in which mortalities over 90 % of the population have been reported. No efficient diagnostic methods are available for this disease, particularly when there are low mite numbers and mild or no clinical signs. In this study, three enzyme-linked immunosorbent assays (ELISA) developed for dog (ELISA A), Cantabrian chamois (Rupicapra pyrenaica parva) (ELISA B) and Alpine chamois (Rupicapra rupicapra) (ELISA C), were evaluated to detect specific antibodies (IgG) to sarcoptic mange in Iberian ibex sera.

METHODS

Serum samples from 131 Iberian ibexes (86 healthy and 45 scabietic) were collected from 2005 to 2012 in the Sierra Nevada Natural and National Parks (southern Spain). Based on visual inspection, ibexes were classified into one of three categories, namely healthy (without scabietic compatible lesions), mildly affected (skin lesions over less than 50 % of the body surface) and severely affected (skin lesions over more than 50 % of the body surface). The optimal cut-off point, specificity, sensitivity and the area under the curve (AUC) were calculated, and the agreement between tests was determined. Moreover, differences in the optical density (OD) related to scabies severity have been evaluated for the best test.

RESULTS

ELISA C showed better performance than the two other tests, reaching higher values of sensitivity (93.0 %) and specificity (93.5 %) against the visual estimation of the percentage of affected skin, chosen as the gold standard. Significantly higher concentrations of specific antibodies were observed with this test in the mildly and severely infested ibexes than in healthy ones.

CONCLUSIONS

Our results revealed that ELISA C was an optimal test to diagnose sarcoptic mange in the Iberian ibex. Further studies characterizing immune response during the course of the disease, including spontaneous or drug induced recovery, should follow in order to better understand sarcoptic mange in Iberian ibex populations.

Sarcoptes scabiei infestation does not alter the stability of ectoparasite communities

Background

The host represents a heterogeneous ecosystem where multiple parasite species co-occur and interact with each other for space and resources. Although these interactions may rule the features of an infracommunity and may shape the infracommunity response to external perturbations, the resilience of ectoparasite communities to new infestations remains poorly explored.

Methods

We analysed the composition of the ectoparasite communities found on 214 individual Iberian ibexes (Capra pyrenaica) inhabiting the Sierra Nevada Natural Space, southern Spain. Using classification and regression trees, we explored how the presence of Sarcoptes scabiei (a highly contagious mite), the off-host environment and the host sex govern the prevalence and abundance of lice and ticks. Null model analysis was applied to assess the impact of S. scabiei on the structure of the ectoparasite communities.

Results

Our results suggest that S. scabiei infestation acts in tandem with off-host environment and host sex to define the prevalence and abundance of lice and ticks. We also provided evidence for differences in species co-occurrence only at the early stages of S. scabiei infestation. Regarding species diversity, we recorded that ectoparasite communities in scabietic ibexes reached a high richness faster than those in healthy individuals.

Conclusions

Even though we show that ectoparasite burden is correlated with S. scabiei infestation, off-host environment and host sex, the species response to S. scabiei infestation and climate seem to be highly variable and influenced by ectoparasite life-history traits. Ectoparasite communities also appear resilient to perturbations which is in agreement with what was previously reported for endoparasites. Future refinement of sample collection and the incorporation of ecological and epidemiological-related variables may allow us to establish causal effects and deepen the knowledge about the mechanisms and consequences of ectoparasite interactions.

Sarcoptic mange breaks up bottom-up regulation of body condition in a large herbivore population

Background

Both parasitic load and resource availability can impact individual fitness, yet little is known about the interplay between these parameters in shaping body condition, a key determinant of fitness in wild mammals inhabiting seasonal environments.

Methods

Using partial least square regressions (PLSR), we explored how temporal variation in climatic conditions, vegetation dynamics and sarcoptic mange (Sarcoptes scabiei) severity impacted body condition of 473 Iberian ibexes (Capra pyrenaica) harvested between 1995 and 2008 in the highly seasonal Alpine ecosystem of Sierra Nevada Natural Space (SNNS), southern Spain.

Results

Bottom-up regulation was found to only occur in healthy ibexes; the condition of infected ibexes was independent of primary productivity and snow cover. No link between ibex abundance and ibex body condition could be established when only considering infected individuals.

Conclusions

The pernicious effects of mange on Iberian ibexes overcome the benefits of favorable environmental conditions. Even though the increase in primary production exerts a positive effect on the body condition of healthy ibexes, the scabietic individuals do not derive any advantage from increased resource availability. Further applied research coupled with continuous sanitary surveillance are needed to address remaining knowledge gaps associated with the transmission dynamics and management of sarcoptic mange in free-living populations.