Scabies Infection While Expressing Human Milk for Critically Ill Infants: Is It Safe?

Background: Scabies infections of the breast in lactating individuals are not well described, especially how maternal infection can impact human milk feeding of hospitalized infants in the intensive care setting. Methods: This case report presents a critically ill female infant with a complex surgical history whose mother had an active scabies infection around the breast postpartum and wished to provide expressed human milk. Results: In this case report, human milk was recommended despite maternal scabies infection. Conclusion: Given the limited information that is known about the risk of scabies transmission in human milk for critically ill infants, this case adds to the knowledge base and supports the call for further research.

First report of interspecific transmission of sarcoptic mange from Iberian ibex to wild boar.

BACKGROUND: Sarcoptic mange is a globally distributed parasitic disease caused by the burrowing mite Sarcoptes scabiei. This mite has a certain degree of host specificity, although interspecific transmission can occur among phylogenetically related species or through prey-predator mediated exposure. In 2018, a wild boar (Sus scrofa) with lesions compatible with sarcoptic mange was hunted in Ports de Tortosa i Beseit Natural Park (PTB, north-eastern Spain), where an active epizootic outbreak of sarcoptic mange is affecting Iberian ibexes (Capra pyrenaica) since 2014. METHODS: A complete necropsy, skin scrapings and skin digestions with hydroxide potassium were performed to confirm the diagnosis. Routine histopathological analysis, toluidine blue staining and immunohistochemistry were used to characterize the lesions and the inflammatory infiltrate. Finally, 10 specific S. scabiei microsatellites were molecularly genotyped through polymerase chain reactions in mites obtained from the affected wild boar. For phylogenetic comparison, mites obtained from sympatric Iberian ibexes and allopatric wild boars and Iberian ibexes from southern Spain were analysed. RESULTS: Sarcoptes scabiei was visually and molecularly identified in the infested wild boar from PTB, causing skin lesions with dermal inflammatory infiltrate rich in T and B cells, which indicate an adaptive immune response. Three S. scabiei genetic clusters were identified: one included mites from southern Iberian ibexes, another included mites from southern wild boars, and a third one distinctively grouped the wild boar from PTB with the sympatric ibexes. CONCLUSIONS: To the authors' knowledge, this is the first reported case of sarcoptic mange in wild boar in Spain and the first documented case of S. scabiei cross-transmission from a wild ruminant host to a wild boar. The wild boar presented an ordinary scabies type reaction, which is typical of the self-limiting infestations reported in other cases of interspecific transmission.

A metapopulation model of social group dynamics and disease applied to Yellowstone wolves.

The population structure of social species has important consequences for both their demography and transmission of their pathogens. We develop a metapopulation model that tracks two key components of a species' social system: average group size and number of groups within a population. While the model is general, we parameterize it to mimic the dynamics of the Yellowstone wolf population and two associated pathogens: sarcoptic mange and canine distemper. In the initial absence of disease, we show that group size is mainly determined by the birth and death rates and the rates at which groups fission to form new groups. The total number of groups is determined by rates of fission and fusion, as well as environmental resources and rates of intergroup aggression. Incorporating pathogens into the models reduces the size of the host population, predominantly by reducing the number of social groups. Average group size responds in more subtle ways: infected groups decrease in size, but uninfected groups may increase when disease reduces the number of groups and thereby reduces intraspecific aggression. Our modeling approach allows for easy calculation of prevalence at multiple scales (within group, across groups, and population level), illustrating that aggregate population-level prevalence can be misleading for group-living species. The model structure is general, can be applied to other social species, and allows for a dynamic assessment of how pathogens can affect social structure and vice versa.

Scabies: Diagnostic and Therapeutic Update.

BACKGROUND: Scabies is globally ubiquitous and is a significant health issue for institutions, the economically disenfranchised, resource-poor areas, and for those with weakened immune systems. Topicals are usually effective, but are cumbersome and expensive to use in large populations and for those nonadherent to topicals. Oral ivermectin became available in Canada for the off-label treatment of scabies in the fall 2018. OBJECTIVES: To review the diagnosis and management of scabies. Dose schedules and concomitant management measures are outlined for scabies simplex and for crusted scabies. Ivermectin use is outlined. METHODS: Medline, colleague discussions, practice review, and experience from managing scabies in institutions. RESULTS: Oral ivermectin is safe, easier to use, cheaper, more effective, and more economical than topicals in widespread institutional scabies, for those nonadherent to topicals, and in crusted scabies. CONCLUSIONS: Oral ivermectin is the treatment of choice in large populations, the nonadherent, and for crusted scabies. Oral ivermectin is produced by Merck Canada as Stromectol 3 mg. The treatment dose for noncrusted scabies is 200 µg/kg, taken in a single dose with food. For example, 15 mg (5 tablets) for a 70 kg person. Retreat in 10-14 days to enhance effectiveness, and perhaps to reduce scabicide resistance.

Kenneth Mellanby Commander of the Order of the British Empire (CBE) (1908-1993). The facts about scabies.

Kenneth Mellanby was a distinguished biologist specialising in entomology. He helped to establish the first university in Nigeria and undertook pioneering work on the use of insecticides in agriculture. However, he will best be remembered for a series of experiments which he undertook on human volunteers during the Second World War. These experiments established the mechanism of transmission of scabies and allowed its effective control at a time when the condition had reached epidemic proportions, causing a significant adverse effect on public morale and military effectiveness. Mellanby's wartime monograph on scabies remains to this day the definitive work on the disease and is still studied by dermatologists. His subsequent book Human Guinea Pigs is a remarkable account of the privations to which wartime volunteers willingly submitted themselves in a way that would have never passed any current medical ethics committee.

Susceptibility of patients receiving chemotherapy for haematological malignancies to scabies.

BACKGROUND: Scabies is a contagious dermatosis. The risk factors for its transmission remain unclear. A scabies outbreak, involving patients who were receiving chemotherapy for haematological malignancies, occurred at our hospital. METHODS: The outbreak population was analysed to determine whether the incidence of scabies was higher among contact patients receiving chemotherapy for haematological malignancies. RESULTS: A patient with crusted scabies was the index case, and 18 of 78 contact healthcare workers (HCWs) and 22 of 135 contact patients were diagnosed with classical scabies. Ten of 17 contact patients with haematological malignancies and 12 of 118 contact patients with other diseases were infected with scabies. The incidence rate was significantly higher among the patients with haematological malignancies (P<0.001). The patients with haematological malignancies had a significantly lower mean minimum neutrophil count than those with other diseases (1159/µL vs 3761/µL, P=0.0012). Most haematological patients did not require special nursing assistance, suggesting that the higher incidence of scabies among these patients resulted from their immunodeficiency rather than greater skin-to-skin contact with infected HCWs. CONCLUSION: Our study suggests that patients receiving chemotherapy for haematological malignancies are more susceptible to scabies than patients with other diseases, and require stricter protection.

Molecular epidemiology of a fatal sarcoptic mange epidemic in endangered San Joaquin kit foxes (Vulpes macrotis mutica).

BACKGROUND: In 2013, sarcoptic mange, caused by Sarcoptes scabiei mites, precipitated a catastrophic decline of the formerly stable urban population of endangered San Joaquin kit foxes (Vulpes macrotis mutica) in Bakersfield, California, USA. In 2019, a smaller sarcoptic mange outbreak affected kit foxes 58 km southwest of Bakersfield in the town of Taft, California. To determine whether the Taft outbreak could have occurred as spillover from the Bakersfield outbreak and whether epidemic control efforts must involve not only kit foxes but also sympatric dogs (Canis lupus familiaris), coyotes (Canis latrans), and red foxes (Vulpes vulpes), we evaluated genotypes and gene flow among mites collected from each host species. METHODS: We used 10 Sarcoptes microsatellite markers (SARM) to perform molecular typing of 445 S. scabiei mites collected from skin scrapings from twenty-two infested kit foxes, two dogs, five coyotes, and five red foxes from Bakersfield, Taft, and other nearby cities. RESULTS: We identified 60 alleles across all SARM loci; kit fox- and red fox-derived mites were relatively monomorphic, while genetic variability was greatest in Bakersfield coyote- and dog-derived mites. AMOVA analysis documented distinct mite populations unique to hosts, with an overall FST of 0.467. The lowest FST (i.e. closest genetic relationship, FST = 0.038) was between Bakersfield and Taft kit fox-derived mites while the largest genetic difference was between Ventura coyote- and Taft kit fox-derived mites (FST = 0.843). CONCLUSIONS: These results confirm the close relationship between the Taft and Bakersfield outbreaks. Although a spillover event likely initiated the kit fox mange outbreak, mite transmission is now primarily kit fox-to-kit fox. Therefore, any large-scale population level intervention should focus on treating kit foxes within the city.

High levels of scabies and malnutrition amongst orphans referred to a hospital in Addis Ababa, Ethiopia.

INTRODUCTION: Orphans are at high risk for neglected tropical diseases (NTDs) and other comorbidities such as malnutrition. We investigated how many orphans suffered from scabies, other NTDs and malnutrition. METHODOLOGY: A descriptive study using medical records of orphans referred to a teaching hospital in Addis Ababa, Ethiopia from December 2014 to December 2018 was done. Files documenting NTDs were reviewed in detail for age, referral diagnosis, and nutritional status. Nutritional assessment was done using the WHO Standard growth curve, classifying children as stunted (height for age Z score < -2SD or wasted (weight for length Z score < -2SD). RESULTS: Of the 852 orphans referred, 23.1% (196/852) was diagnosed with scabies, amongst which 28.1% (55/196) had multiple episodes. The median age (interquartile range) of the children with scabies was 3 (2-5) months. 85.2% (169/196) of the orphans with scabies were stunted and /or wasted. No other NTDs were reported. All of the scabies cases identified were not documented in the referral letter of the orphanage. CONCLUSIONS: There is ongoing transmission of scabies among children in the orphanage. Amongst orphans with scabies, an alarmingly high percentage was malnourished. Referrals from orphanages may provide an opportunity to detect NTDs and this is being missed.

A nosocomial scabies outbreak originating from immunocompromised transplant patients in Turkey: Upholstery as a possible cause.

BACKGROUND: Inpatients with crusted scabies represent an important source of nosocomial transmission with consequent outbreaks among patients and healthcare workers. This study aimed to report the course of an institutional scabies outbreak, which progressed with infestation of immunosuppressed transplant patients, health care workers, and caregivers. METHODS: Patients diagnosed with scabies in a nosocomial outbreak in a 200-bed, tertiary hospital were included. Following a diagnosis of scabies in the index patient, strict contact isolation measures were implemented. During the outbreak, a root cause analysis (RCA) was carried out by an infection prevention and control team. RESULTS: Forty-two individuals were affected (7 patients, 25 health care workers, and 10 family members of the patients) during the outbreak consisting of three attacks. Index case was a multiple myeloma patient who received hematopoietic stem cell transplantation and presented with crusted scabies. A RCA suggested that upholstery could serve as a means of reservoir. All upholstery of the sofa and armchairs in patient rooms as well as in lounge areas were replaced by wipeable leather material. After the 19-week course of the outbreak, no additional cases of scabies have been observed until now. CONCLUSION: A high index of suspicion should be maintained, particularly in immunocompromised patients, in order to achieve rapid diagnosis of scabies and to implement institutional infection control measures. It should also be borne in mind that the transmission may occur through direct contact as well as fomites, such as upholstery.

Possible transmission of Sarcoptes scabiei between herbivorous Japanese serows and omnivorous Caniformia in Japan: a cryptic transmission and persistence?

BACKGROUND: Two transmission patterns of Sarcoptes scabiei in host mammal communities have been reported based on microsatellite-level genetic studies in the last two decades. While one involves restrictions among different host taxa, the other is associated with predator-prey interactions between different host taxa. In contrast to these observations, the present study reports a possible irregular case of transmission of S. scabiei between herbivorous Japanese serow and omnivorous Caniformia mammals in Japan, though under very weak predator-prey relationships. METHODS: DNA from 93 Sarcoptes mites isolated from omnivorous Caniformia (such as the domestic dog, raccoon dog, raccoon and Japanese marten), omnivorous Cetartiodactyla (wild boar) and herbivorous Cetartiodactyla (Japanese serow) in Japan were analyzed by amplifying nine microsatellite markers. Principal components analyses (PCA), Bayesian clustering analyses using STRUCTURE software, and phylogenetic analyses by constructing a NeighborNet network were applied to determine the genetic relationships among mites associated with host populations. RESULTS: In all the analyses, the genetic differentiation of Sarcoptes mites from wild boars and Japanese serows was observed. Conversely, considerably close genetic relationships were detected between Caniformia-derived and Japanese serow-derived mites. Because the predator-prey interactions between the omnivorous Caniformia and herbivorous Japanese serow are quite limited and epidemiological history shows at least a 10-year lag between the emergence of sarcoptic mange in Japanese serow and that in Caniformia, the transmission of S. scabiei from Caniformia to Japanese serow is highly suspected. CONCLUSIONS: The close genetic relationships among mites beyond Host-taxon relationships and without obvious predator-prey interactions in Caniformia and Japanese serow deviate from previously reported S. scabiei transmission patterns. This type of cryptic relationship of S. scabiei populations may exist in local mammalian communities worldwide and become a risk factor for the conservation of the remnant and fragmented populations of wild mammals.

Sarcoptic Mange of Fox Origin in Multiple Farm Animals and Scabies in Humans, Switzerland, 2018.

Fox-derived Sarcoptes scabiei mites caused an outbreak of mange on a farm in Switzerland in 2018. Pruritic skin lesions suggestive of S. scabiei mite infestation developed in 4 humans who had direct contact with affected farm animals but not foxes. Sarcoptic mange is continuously spreading; such outbreaks affecting humans could start occurring more frequently.

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.

Assessing the role of dens in the spread, establishment and persistence of sarcoptic mange in an endangered canid.

Sarcoptic mange is a skin disease caused by the mite Sarcoptes scabiei that can devastate populations of wild species. S. scabiei can survive off-host and remain infective for specific periods. In den-dwelling species, dislodged mites could be protected from the environmental conditions that impair their survival thus supporting pathogen transmission. To assess the potential role of dens in the spread, establishment, and persistence of sarcoptic mange in a population of hosts, we constructed an agent-based model of the endangered San Joaquin kit fox (SJKF; Vulpes macrotis mutica) population in Bakersfield, California, that explicitly considered the denning ecology and behavior of this species. We focused on this SJKF urban population because of their vulnerability and because a sarcoptic mange epizootic is currently ongoing. Further, SJKF is a social species that lives in family groups year-round and contact between individuals from different family groups is rare, but they will occupy the same dens intermittently. If mites remain infective in dens, they could support intra-family disease transmission via direct (den sharing) and indirect (contaminated den) contact, but also inter-family transmission if susceptible individuals from different families occupy contaminated dens. Simulations showed that den-associated transmission significantly increases the chances for the mite to spread, to establish and to persist. These findings hold for different within-den S. scabiei off-host survival periods assessed. Managers dealing with S. scabiei in this species as well as in other den-dwelling species should consider den-associated transmission as they could be targeted as part of the control strategies against this mite.

A biological model of scabies infection dynamics and treatment informs mass drug administration strategies to increase the likelihood of elimination.

Infections with Sarcoptes scabiei, or scabies, remain common in many disadvantaged populations. Mass drug administration (MDA) has been used in such settings to achieve a rapid reduction in infection and transmission, with the goal of eliminating the public health burden of scabies. While prevalence has been observed to fall substantially following such an intervention, in some instances resurgence of infection to baseline levels has occurred over several years. To explore the biology underpinning this phenomenon, we have developed a theoretical model of scabies life-cycle and transmission dynamics in a homogeneously mixing population, and simulate the impact of mass drug treatment strategies acting on egg and mite life cycle stages (ovicidal) or mites alone (non-ovicidal). In order to investigate the dynamics of the system, we first define and calculate the optimal interval between treatment doses. We calculate the probability of eradication as a function of the number of optimally-timed successive treatment doses and the number of years over which a program is run. For the non-ovicidal intervention, we first show that at least two optimally-timed doses are required to achieve eradication. We then demonstrate that while more doses over a small number of years provides the highest chance of eradication, a similar outcome can be achieved with fewer doses delivered annually over a longer period of time. For the ovicidal intervention, we find that doses should be delivered as close together as possible. This work provides a platform for further research into optimal treatment strategies which may incorporate heterogeneity of transmission, and the interplay between MDA and enhancement of continuing scabies surveillance and treatment strategies.

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.

Calculation of the age of the first infection for skin sores and scabies in five remote communities in northern Australia.

Prevalence of skin sores and scabies in remote Australian Aboriginal communities remains unacceptably high, with Group A Streptococcus (GAS) the dominant pathogen. We aim to better understand the drivers of GAS transmission using mathematical models. To estimate the force of infection, we quantified the age of first skin sores and scabies infection by pooling historical data from three studies conducted across five remote Aboriginal communities for children born between 2001 and 2005. We estimated the age of the first infection using the Kaplan-Meier estimator; parametric exponential mixture model; and Cox proportional hazards. For skin sores, the mean age of the first infection was approximately 10 months and the median was 7 months, with some heterogeneity in median observed by the community. For scabies, the mean age of the first infection was approximately 9 months and the median was 8 months, with significant heterogeneity by the community and an enhanced risk for children born between October and December. The young age of the first infection with skin sores and scabies reflects the high disease burden in these communities.