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.

First detection of Sarcoptes scabiei from domesticated pig (Sus scrofa) and genetic characterization of S. scabiei from pet, farm and wild hosts in Israel.

In this report we describe for the first time the detection of Sarcoptes scabiei type suis mites on domestic pigs in Israel and examine its genetic variation compared with S. sabiei from other hosts. Microscopic examination of skin samples from S. scabiei-infested pigs (Sus scrofa domesticus) revealed all developmental stages of S. scabiei. To detect genetic differences between S. scabiei from different hosts, samples obtained from pig, rabbits (Orictolagus cuniculus), fox (Vulpes vulpes), jackal (Canis aureus) and hedgehog (Erinaceus concolor) were compared with GenBank-annotated sequences of three genetic markers. Segments from the following genes were examined: cytochrome C oxidase subunit 1 (COX1), glutathione-S-transferase 1 (GST1), and voltage-sensitive sodium channel (VSSC). COX1 analysis did not show correlation between host preference and genetic identity. However, GST1 and VSSC had a higher percentage of identical sites within S. scabiei type suis sequences, compared with samples from other hosts. Taking into account the limited numbers of GST1 and VSSC sequences available for comparison, this high similarity between sequences of geographically-distant, but host-related populations, may suggest that different host preference is at least partially correlated with genetic differences. This finding may help in future studies of the factors that drive host preferences in this parasite.

Scabies: a review of diagnosis and management based on mite biology.

Scabies is a contagious parasitic dermatitis that is a significant cause of morbidity, especially outside of the United States. Scabies is diagnosed most often by correlating clinical suspicion with the identification of a burrow. Although scabies should be on the differential for any patient who presents with a pruritic dermatosis, clinicians must consider a wide range of diagnostic possibilities. This approach will help make scabies simultaneously less over- and underdiagnosed by clinicians in the community. Atypical or otherwise complex presentations may necessitate the use of more definitive diagnostic modalities, such as microscopic examination of KOH prepared skin scrapings, high-resolution digital photography, dermoscopy, or biopsy. Scabies therapy involves making the correct diagnosis, recognizing the correct clinical context to guide treatment of contacts and fomites, choosing the most effective medication, understanding how to use the agent properly, and following a rational basis for when to use and reuse that agent. Although the development of new therapeutic agents is always welcome, tried and true treatments are still effective today. Permethrin is the gold standard therapy, with malathion being an excellent topical alternative. Ivermectin is an effective oral alternative that is especially useful in crusted scabies, patients who are bed ridden, and in institutional outbreaks. Despite the availability of effective therapeutics, treatment failures still occur, mostly secondary to application error (ie, failure to treat the face and scalp or close contacts, failure to reapply medication) or failure to decontaminate fomites. Because increasing resistance to scabies treatments may be on the horizon, we propose that standard of care for scabies treatment should involve routine treatment of the scalp and face and re-treating patients at day 4 on the basis of the scabies life cycle to ensure more efficient mite eradication. Practitioners should attempt to treat all close contacts simultaneously with the source patient. To eradicate mites, all fomites should be placed in a dryer for 10 minutes on a high setting, furniture and carpets vacuumed, and nonlaunderables isolated for a minimum of 2 days, or, for those who wish to be rigorous, 3 weeks.

The immunology of susceptibility and resistance to scabies.

The transmission of scabies occurs with the burrowing of Sarcoptes scabiei var. hominis mites into the skin. Infestation invariably leads to the development of localized cutaneous inflammation, pruritus and skin lesions. Classical transmission studies document an initial increase in S. scabiei numbers subsequent to primary infestation with a gradual reduction as host immunity develops. However, certain individuals fail to control infection and develop severe crusting of the skin, accompanied with extremely high mite burdens, elevated antibody levels and eosinophilia. These individuals have the nonhealing form of the human disease known as crusted scabies. The genetic predisposition for susceptibility or resistance to S. scabiei infection in humans is hypothesized to correlate with the dominance of an IgE-driven Th2 response in severe disease or an interferon-gamma-dominated Th1 response that promotes parasite control. However, recent data reveals complexities in cytokine regulation in the skin and the mechanisms of acquired resistance and immune escape. In this review, we consider the recent immunological and biomolecular advances in understanding the human host immune response to S. scabiei infestations in the context of earlier studies and attempt to reconcile apparent differences and emphasize those aspects of the Th1/Th2 model that are supported or refined.

A case of hyperkeratotic crusted scabies.

Patients who are immunocompromised or have cognitive or physical disabilities are at a higher risk of being affected with infections such as crusted scabies. This is a rare skin hyperinfestation by Sarcoptes scabiei var. hominis. The main characteristic of this dermatosis is a thick crust due to the high concentration of mites; in addition, other manifestations such as papules, excoriations, and burrows may be absent. In severe cases, thick yellow-brown crusts and plaques with deep fissures are present. Diagnosis can be made by observing mites, ova, or feces from skin scrapings. Multiple therapies can be used in patients with this condition. Management with patient isolation is important to prevent institutional outbreaks. This disease can have high mortality, primarily due to sepsis. Awareness of this condition and its serious consequences is important to reduce its mortality and morbidity.

Comparative analysis of host resistance to Sarcoptes scabiei var. cuniculi in two different rabbit breeds.

BACKGROUND: Scabies, caused by infestation of the mite Sarcoptes scabiei, is one of the most severe ectoparasitic diseases in rabbits. Scabies seriously affects the commercial rabbit breeding, causing severe economic losses. Host resistance to S. scabiei is an important factor in further development of the rabbit industry. In the present study, we compared the host resistance to S. scabiei var. cuniculi of a new breed of domestic rabbit propagated by the Sichuan Animal Sciences Academy (QiXing rabbit, QX) compared with that of a traditional rabbit breed in the domestic rabbit industry (IRA rabbit, IRA). METHODS: Both QX and IRA rabbits were experimentally infested with live S. scabiei var. cuniculi mites for 48 h. Then, during the course of four-week experimental infestation period, the body weight of rabbits was recorded every two weeks for calculating body-weight variations in comparison to the non-infested control rabbits. Skin lesions in the foot area were assessed on weekly basis and serum samples were tested weekly for the estimation of changes in the total antibody levels (IgG, IgE and IgM). Moreover, DNA extracted from the blood samples was amplified for analysis of the genetic diversity in the major histocompatibility complex, class II, DQ Alpha (MHC-DQA) gene. RESULTS: Compared to the IRA rabbits, the QX rabbits showed a significantly higher (P < 0.05) relative body weight gain compared to the non-infested control rabbits and significantly lower (P < 0.05) scores for foot skin lesions and higher levels of IgG, IgE and IgM at weeks 1 to 4, week 2 and week 1 post-infestation, respectively. Furthermore, a polymorphism site at position 103 bp of exon two of MHC-DQA gene and a different gene frequency were found between two rabbit breeds, suggesting the genetic basis for the differential host resistance to the S. scabiei var. cuniculi between two rabbit breeds. CONCLUSIONS: The QX rabbits showed higher host resistance to S. scabiei var. cuniculi compared to the IRA rabbits at the clinical, immunological and genetic levels. These results provide a reference for the breeding of rabbits with adequately improved and sustained host resistance to scabies in the domestic rabbit industry.

A systematic review of scabies transmission models and data to evaluate the cost-effectiveness of scabies interventions.

BACKGROUND: Scabies is a common dermatological condition, affecting more than 130 million people at any time. To evaluate and/or predict the effectiveness and cost-effectiveness of scabies interventions, disease transmission modelling can be used. OBJECTIVE: To review published scabies models and data to inform the design of a comprehensive scabies transmission modelling framework to evaluate the cost-effectiveness of scabies interventions. METHODS: Systematic literature search in PubMed, Medline, Embase, CINAHL, and the Cochrane Library identified scabies studies published since the year 2000. Selected papers included modelling studies and studies on the life cycle of scabies mites, patient quality of life and resource use. Reference lists of reviews were used to identify any papers missed through the search strategy. Strengths and limitations of identified scabies models were evaluated and used to design a modelling framework. Potential model inputs were identified and discussed. FINDINGS: Four scabies models were published: a Markov decision tree, two compartmental models, and an agent-based, network-dependent Monte Carlo model. None of the models specifically addressed crusted scabies, which is associated with high morbidity, mortality, and increased transmission. There is a lack of reliable, comprehensive information about scabies biology and the impact this disease has on patients and society. DISCUSSION: Clinicians and health economists working in the field of scabies are encouraged to use the current review to inform disease transmission modelling and economic evaluations on interventions against scabies.

Sarcoptic mange in wild raccoon dogs (Nyctereutes procyonoides) in Korea.

Infestation with Sarcoptes scabiei was diagnosed from four wild raccoon dogs (Nyctereutes procyonoides) accidentally captured and presented to the Animal Health Center in Seoul Grand Park Zoo, Korea. Diagnosis was done by microscopic and histologic examination from skin lesions. Sarcoptes scabiei was the only species detected from the lesions and characterized by dorsoventrally flattened and round bodies, sucker-like pulvilli borne on long nonjointed pretarsi, triangular scales and spinelike setae on the dorsum, and three epimeres that are chitinous extensions of the coxae of the legs. In addition, infiltration of mast cells in the dermis was associated with infestation of the burrowing mite. This is the first report of sarcoptic mange in raccoon dogs in Korea. Because heavy infestation with S. scabiei was found in all of the captured wild raccoon dogs, further work is necessary to develop prophylactic interventions to prevent the spread of sarcoptic mange in free-living raccoon dogs in Korea.

Sarcoptic mange and Pelodera dermatitis in an American black bear (Ursus americanus).

An adult female free-ranging American black bear (Ursus americanus) was presented in poor body condition, with advanced skin disease. Skin changes included hair loss, lichenification, crusting, and focal erosions. Skin scrapings and histopathology identified two distinct parasitic conditions that were contributing to this animal's dermatitis. Large numbers of larvae, nymphs, and adults of Sarcoptes scabiei were present in the superficial epidermis, and nematodes consistent with Pelodera strongyloides were abundant within the hair follicles. This appears to be the first reported case of Pelodera dermatitis in a bear species, adding a new differential agent to the list for dermatitis in bears. The sarcoptic mange and poor body condition of this bear may have been contributing factors to the development of the opportunistic Pelodera infestation.

Molecular characterization and allergenicity potential of triosephosphate isomerase from Sarcoptes scabiei.

Scabies is an allergic skin disease that affects millions of mammals worldwide, including humans. It is a neglected tropical disease that represents a significant public health threat, particularly in economically disadvantaged populations. An effective vaccine is not currently available, and the exact mode of pathogenesis remains unclear. Herein, we identified, cloned and recombinantly expressed triosephosphate isomerase from Sarcoptes scabiei (S. scabiei). Immunohistochemical analyses showed that S. scabiei triosephosphate isomerase (Ss-TIM) is localized in the legs and chewing mouthparts of mites, and in infected rabbit skin (keratinized skin and embedded mites). Intradermal skin tests of rabbits injected with recombinant S. scabiei triosephosphate isomerase (rSs-TIM) revealed a flare, erythema and wheal reaction. These findings suggest that Ss-TIM may contribute to host invasion and induce an allergic response in the host.

Scabies.

Scabies is a neglected parasitic disease that is a major public health problem in many resource-poor regions. It causes substantial morbidity from secondary infections and post-infective complications such as acute post-streptococcal glomerulonephritis. Disease control requires treatment of the affected individual and all people they have been in contact with, but is often hampered by inappropriate or delayed diagnosis, poor treatment compliance, and improper use of topical compounds such as permethrin, lindane, or benzyl benzoate. In addition to concerns over toxicity with such compounds, parasite resistance seems to be increasing. Oral ivermectin is an alternative that has been used successfully in community control programmes. Plant derivatives such as turmeric, neem, and tea tree oil are also promising future treatments. The disease is strongly associated with poverty and overcrowding, and the associated stigma can ostracise affected individuals. Treatment of scabies in poor countries needs to integrate drug treatment programmes with efforts to improve the socioeconomic conditions and education programmes to reduce stigma. We expect the future to bring more sensitive and specific clinical and laboratory-based diagnostic methods, as well as new therapeutic strategies.

Comparison of ivermectin and benzyl benzoate lotion for scabies in Nigerian patients.

Few studies have compared ivermectin directly with topical agents in developing countries. We compared the effectiveness of oral ivermectin (200 microg/kg) with topical 25% benzyl benzoate and monosulfiram soap in 210 subjects of age 5 to 65 years with scabies. Subjects with persistent lesions after 2 weeks received a second course of treatment. All lesions had resolved after 2 weeks in 77 of 98 (79%) subjects treated with ivermectin and in 60 of 102 (59%) subjects treated topically (P = 0.003). The improvement in severity score was greater in the ivermectin group than in the topical treatment group (P < 0.001). The overall cure rate after 4 weeks was 95% in the ivermectin group and 86% in the topical treatment group (P = 0.04). Compared with topical benzyl benzoate and monosulfiram in the treatment of scabies, ivermectin was at least as effective and led to more rapid improvement.

Epidemiological study of scabies in different environmental conditions in central poland.

PURPOSE: The goal of the research was to determine the spreading of Sarcoptes scabiei and the incidence of scabies in the residents of particular districts of the Swietokrzyskie Voivodeship (Central Europe) from 1990 to 1998. METHODS: An epidemiological analysis of scabies incidents was performed, with a focus on the age and sex patterns of the population, seasonal incidence, and environmental conditions. In the entire area covered in the period studied, a total of 2064 cases of scabies were reported. The incidence of scabies was typically higher in rural areas than in cities. The most cases of scabies were noted in children and teenagers between 6 and 15 years of age. RESULTS: The research indicated that prevalence of the disease within a family is an important factor in scabies epidemiology in the Swietokrzyskie Voivodeship. The incidence of scabies is seasonal in its nature, as the majority of cases occurred in the autumn and winter months. CONCLUSION: The incidence of the disease can be reduced by improving socioeconomic and hygienic conditions and by implementing a proper system of social education, as well as by promoting more efficient health service.

[A baby with an unexplained skin rash]. / Een zuigeling met een onbegrepen huiduitslag.

A 2-month-old infant presented with papules and pustules. Since the patient's mother and brother also had an unexplained--itchy--skin rash, it was thought that the skin rash was due to scabies. This diagnosis was confirmed by dermatoscopy and direct microscopic examination.

Efficacy of afoxolaner in a clinical field study in dogs naturally infested with Sarcoptes scabiei.

The acaricidal efficacy of afoxolaner (NexGard(®), Merial) was evaluated against Sarcoptes scabiei var. canis in a field efficacy study, when administered orally at a minimum dose of 2.5 mg/kg to dogs naturally infested with the mites. Twenty mixed-breed dogs of either sex (6 males and 14 females), aged over 6 months and weighing 4-18 kg, were studied in this randomised controlled field efficacy trial. Dogs, naturally infested with Sarcoptes scabiei var. canis confirmed by skin scrapings collected prior to allocation, were randomly divided into two equal groups. Dogs in Group 1 were not treated. Dogs in Group 2 were treated on Days 0 and 28. On Days 0 (pre-treatment), 28 (pre-treatment) and 56, five skin scrapings of similar size were taken from different sites with lesions suggestive of sarcoptic mange. The extent of lesions was also recorded on Days 0, 28 and 56, and photographs were taken. Dogs treated orally with afoxolaner had significantly (p < 0.001) lower mite counts than untreated control animals at Days 28 and 56 with no mites recovered from treated dogs at these times (100% efficacy based on mite counts). In addition, dogs treated with NexGard had significantly (p < 0.05) better lesion resolution at Day 56 than Day 0; no treated dog showed pruritus compared to 7/10 dogs in the control group, 1/9 treated dogs had crusts compared to 5/10 controls and 8/9 dogs recovered 90% of hairs on lesions compared to 0/10 control dogs.

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.