Experimental transmission of a goat strain of Sarcoptes scabiei to desert sheep and its treatment with ivermectin

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 The systematic review of all the information on diseases affecting the species unveils unpublished reports, scientific communications in meetings, and scientific articles, allowing the first comprehensive compilation of Iberian ibex diseases.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.

Sarcoptic mange outbreak decimates South American wild camelid populations in San Guillermo National Park, Argentina

Sarcoptic mange epidemics can devastate wildlife populations. In 2014, mange was first detected in vicuñas (Vicugna vicugna) and guanacos (Lama guanicoe) in San Guillermo National Park (SGNP), Argentina. This study describes the temporal dynamics of the outbreak, its effects on the park's wild camelid populations between 2017-2019, and investigates the potential source of the epidemic. From May 2017 to June 2018, transect surveys indicated a sharp decrease in the density of living vicuñas and guanacos by 68% and 77%, respectively. By April 2019 no vicuñas or guanacos were recorded on transect surveys, suggesting their near-extinction in the park. Clinical signs consistent with mange (e.g., intense scratching, hyperkeratosis, alopecia) were observed in 24% of living vicuñas (n = 478) and 33% of living guanacos (n = 12) during surveys, as well as in 94% of vicuña carcasses (n = 124) and 85% of guanaco carcasses (n = 20) examined. Sarcoptes scabiei was identified as the causal agent by skin scrapings, and the cutaneous lesions were characterized by histopathology (n = 15). Genetic characterization revealed that mites recovered from seven vicuñas (n = 13) and three guanacos (n = 11) shared the same genotype, which is consistent with a single source and recent origin of the epidemic. Tracing the potential source, we identified a governmental livestock incentive program which introduced llamas (Lama glama) in areas adjacent to SGNP in 2009, some of which had alopecic scaling consistent with sarcoptic mange. Though at the time of our study no llamas with mange were available for confirmatory sampling, we hypothesize that the introduction of mange-infected llamas may have triggered the outbreak in wild camelids. This unprecedented event in SGNP had devastating effects on dominating herbivores with potentially profound cascading effects at the community and ecosystem levels.

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.

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.

Effects of temperature on the survival of Sarcoptes scabiei of black bear (Ursus americanus) origin

For two decades, the incidence and range of sarcoptic mange in black bears (Ursus americanus) in Pennsylvania has increased. The causative agent, Sarcoptes scabiei, can be directly or indirectly transmitted; therefore, data on environmental persistence is important for guiding management and public communications. The objective of this study was to determine the survival of S. scabiei at different temperatures. Full section skin samples and superficial skin scrapes were collected from bears immediately after euthanasia due to severe mange. After ~ 24 h on ice packs (shipment to lab), samples were placed in dishes at 0, 4, 18, or 30 °C and 60, 20, 12, and 25% relative humidity, respectively, and the percentage of mites alive, by life stage, was periodically determined. Humidity was recorded but not controlled. Temperature significantly affected mite survival, which was shortest at 0 °C (mostly ≤ 4 h) and longest at 4 °C (up to 13 days). No mites survived beyond 8 days at 18 °C or 6 days at 30 °C. Mites from full-thickness skin sections survived significantly longer than those from superficial skin scrapes. Adults typically survived longer than nymphs and larvae except at 30 °C where adults survived the shortest time. These data indicate that at cooler temperatures, S. scabiei can survive for days to over a week in the environment, especially if on host skin. However, these data also indicate that the environment is unlikely to be a long-term source of S. scabiei infection to bears, other wildlife, or domestic animals.

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).

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.

The neglected navigating web of the incomprehensibly emerging and re-emerging Sarcoptes mite

Parasite presence in any ecosystem generates complex navigating webs (Parasite-NW) within the system, through which parasites move from one to another host. The appropriate assimilation of parasite navigating web is pivotal for a better understanding of pathogen flow in the ecosystem, with implications for disease control. Sarcoptes mite has been approached from medical, veterinary, entomological, physiological and, recently, molecular sides, to understand its epidemiological navigating web between isolates from different hosts and geographical regions. The obtained conclusions are still a matter of debate. Sarcoptes navigating web (Sarcoptes-NW) is intricate and uncertain, with unexplainable pathogenic flow. In this review we summarize by which routes, under what conditions and at what levels the Sarcoptes mite moves among its hosts.

Moxidectin efficacy in a goat herd with chronic and generalized sarcoptic mange

A case of sarcoptic mange affecting almost all the animals of a dairy goat herd is described. This pruritic skin disease led progressively to high mortality and dramatic drop of milk yield. The lesions of the affected goats were typical of a chronic and generalized-diffuse sarcoptic mange. Diagnosis was confirmed by skin scrapings and histopathology in which many mites were demonstrated. All surviving goats were treated with injectable moxidectin solution 1% (CYDECTIN-Fort Dodge) at the dose of 0.2 mg/kg, applied every 15 days for four times, subcutaneously. Although pruritus had decreased soon after the first treatment, a satisfactory healing of cutaneous lesions was witnessed 6 weeks after the beginning of moxidectin trial. Parasitological cure was achieved in all affected animals by the end of the trial. In the four monthly followups, no evidence of sarcoptic mange could be found.

Usefulness of estimated surface area of damaged skin as a proxy of mite load in the monitoring of sarcoptic mange in free-ranging populations of Iberian wild goat, Capra pyrenaica

In this study we examined the influence of several factors, like the surface of skin with lesions attributable to Sarcoptes scabiei, the time of year and host sex and age on variations of mite load in Iberian wild goats, Capra pyrenaica, from the Sierra Nevada Natural Space, southern Spain. As well, the surface area of skin with scabietic lesions estimated during field surveys were compared with measurements taken in the laboratory and the potential for using categories based on surface areas estimated during monitoring and management programs was analyzed. The surface area of the skin lesions measured in the laboratory and the time of year were the main factors affecting mite load. Results also revealed discrepancies between the surface area of lesions estimated in the field and those measured in the laboratory. The highest error percentages were associated with lesions ranging between 25 and 75% of host skin surface area. By reducing the number of categories of mange infestation (from 5 to 3) the proportion of cases correctly classified using data from field surveys increases. Our analyses suggest that the estimated surface areas of scabietic lesions is a useful relative index of mite abundance and/or intensity of parasitation in Iberian wild goat. Therefore, we conclude that revised classifications should be used in the monitoring of sarcoptic mange in wild populations, since data can be obtained in an inexpensive, fast and non-invasive fashion.

Sarcoptic mange of gazelle (Gazella subguttarosa) and its medical importance in Iran

Sarcoptes scabiei infestation was diagnosed in four freshly dead and three net-captured gazelle while ranging freely. The captured animals presented with an alopecic pruritic skin disease with signs of crusted skin lesions, numerous small nodules which first appeared on the lips or nostrils and then it also extended towards the eyelids, around the ears, and, in some cases, over entire face, neck, trunk, and legs. Skin over the affected area gradually became bald, thick and hard, being dry and doughy to the touch, and serous fluid or sometimes blood oozes from the lesions which had a severe malodor. Skin scrapings confirmed the presence of the mite S. scabiei. Histopathology of lesions demonstrated marked acanthosis, hyperkeratosis, and parakeratosis. Microscopical examination also revealed all stages of S. scabiei, which were located mainly in the stratum corneum and also in the stratum granulosum. During the capture and sampling of the animals, four persons ranging in age from 25 to 62 years were exposed to scabies. Two relatives of one of them have been also affected by familiar contact. Clinical signs appeared within 9 days of exposure. They developed several pruretic erythematous papules with intense itching.

Ectoparasite control in small ruminants

Ectoparasites are a common problem in small ruminants of North America. Management of ectoparasites in small ruminants can be challenging for producers and veterinarians. It is important for the veterinarian to make an accurate diagnosis of the type of ectoparasite that is infesting the animal, then to develop a plan that most effectively and economically controls the ectoparasite. Effective and economic control of an ectoparasite infestation begins with an understanding of the ectoparasite's life cycle and how that life cycle affects the animal. It should be noted that climate and geographical area can affect the life cycle of specific ectoparasites, so it is important for veterinarians to educate themselves about their specific environment. Once the life cycle has been addressed, then the veterinarian should decide which intervention will provide the best control. Intervention possibilities may range from insecticides to environmental management or a combination of several methods. The veterinarian should provide the producer with realistic goals that define specific limitations of ectoparasite control.

Experimental infection of chamois (Rupicapra pyrenaica parva) with Sarcoptes scabiei derived from naturally infected goats

Two chamois (Rupicapra pyrenaica parva) out of a group of three were experimentally infected with Sarcoptes scabiei derived from a naturally infected domestic goat. One of the chamois presented the first clinical manifestations (papules and desquamation) at 7 days post-infection, after 22 days crusts and alopecia appeared and after 41 days pruritus. The other chamois presented desquamation after 15 days and papules after 21 days and crusts and alopecia after 31 days. All these clinical manifestations continued to spread and when the animals were treated at 84 days post-infection, pruritus, papules and crusts were first to disappear, there being no evidence of their presence at 99 days post-infection, when the second treatment dose was applied. The desquamation and alopecia disappeared at 114 days post-infection, by which stage both animals were considered to have been cured. The results of the skin scraping was negative in both chamois until 54 days post-infection and it became negative again after 84 days, when the first treatment dose was applied. Biopsies showed different levels of hyperkeratosis and a marked epidermic hyperplasia with formation of small crusts. Superficial epidermis presented marked vasodilatation and also infiltrated inflammation. None of the biopsies carried out showed the presence of parasites. The non-infected chamois, which was kept in the same compound as the other two, did not present any clinical manifestations compatible with infection by S. scabiei throughout the entire period of the experiment.

Efficacy of moxidectin against sarcoptic mange and effects on milk yield of ewes and growth of lambs

Forty-eight dairy ewes and 45 lambs naturally infested with sarcoptic mange, were divided into three equal groups and treated with moxidectin 1% inj. sol. at a dose rate of 0.2 mg moxidectin kg(-1) bodyweight once or twice ten days apart. During the study, the skin lesions were scored and the number of mites recovered in facial skin scrapings from the animals were recorded. Moxidectin was found to be effective against ovine sarcoptic mange, when given twice; the percentage reduction of mites was 100% (p < 0.0001) and the skin lesions disappeared completely (p = 0.0001). In sheep treated once only, the percentage reduction of mites varied from 75% to 92%. Treated ewes produced up to 22.4% more milk than the infested ones (p = 0.0001). Treated lambs had up to 15% greater final weight and up to 23.7% more growth than infested controls (p = 0.0001). It is concluded that two injections of moxidectin 1% inj. sol. at a dose rate of 0.2 mg kg(-1) bodyweight, given ten days apart, were effective against ovine sarcoptic mange. Furthermore, it is considered that sarcoptic mange adversely affects the production of the infested animals.