Scabies.

Scabies is one of the most common and highest-burden skin diseases globally. Estimates suggest that >200 million people worldwide have scabies at any one time, with an annual prevalence of 455 million people, with children in impoverished and overcrowded settings being the most affected. Scabies infection is highly contagious and leads to considerable morbidity. Secondary bacterial infections are common and can cause severe health complications, including sepsis or necrotizing soft-tissue infection, renal damage and rheumatic heart disease. There is no vaccine or preventive treatment against scabies and, for the past 30 years, only few broad-spectrum antiparasitic drugs (mainly topical permethrin and oral ivermectin) have been widely available. Treatment failure is common because drugs have short half-lives and do not kill all developmental stages of the scabies parasite. At least two consecutive treatments are needed, which is difficult to achieve in resource-poor and itinerant populations. Another key issue is the lack of a practical, rapid, cheap and accurate diagnostic tool for the timely detection of scabies, which could prevent the cycle of exacerbation and disease persistence in communities. Scabies control will require a multifaceted approach, aided by improved diagnostics and surveillance, new treatments, and increased public awareness.

The association between knockdown resistance and treatment outcome of 1% permethrin lotion in head lice infestations in Nonthaburi province, Thailand.

Head lice infestations significantly impact schoolchildren, with permethrin being the primary treatment. The escalation in the prevalence of the knockdown resistance (kdr) mutation, potentially affecting treatment efficacy, is highly concerning. This study examined head lice infestation prevalence, the efficacy of 1% permethrin lotion, kdr mutation frequency, and the association between kdr genotype and permethrin treatment outcomes in schoolchildren in Nonthaburi province, Thailand. Participants and lice samples were collected from six primary schools using cluster sampling. Clinical outcomes and adverse events were assessed on days 7 and 14 post-treatment. Kdr mutations (T917I) in head lice samples were analyzed using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. Head lice infestation prevalence was 6.1%, with a kdr mutation frequency of 63.2% and a permethrin cure rate of approximately 50%. Multivariate regression analysis revealed the association between kdr genotype and clinical response to permethrin treatment (Odds Ratio (OR) = 13.15, p = 0.005). The presence of resistance genes hinders the cure rate (presence 35.9% versus absence 85.7%). These findings highlight the importance of the kdr genotype in predicting permethrin treatment responses in head lice infestations. Furthermore, in regions with documented reduced permethrin efficacy and a high prevalence of kdr mutations, alternative non-pyrethroid-based pediculicides should be considered. This research could help improve the control of head lice infestations, especially in problematic areas of Thailand.

Homogeneity of pharmacological prescription and control measures applied in cases of scabies detected amongst inmates in Catalonia.

OBJECTIVES: To review the homogeneity of pharmacological prescription and control measures applied in cases of scabies in prisons in Catalonia. MATERIAL AND METHOD: Observational, multicenter, and retrospective study. Cases of scabies from March 01, 2021 and March 01, 2022 were analyzed according to the International Alliance for the Control of Scabies (IACS) 2020 criteria: a) confirmed cases; b) clinically probable cases; and c) suspected cases.Epidemiological, clinical, therapeutic and regimental control variables were collected. We checked whether the interventions were homogeneous in each site. The mean and standard deviation were used as continuous variables and percentages and confidence interval (95%) for discrete variables. The Chi-square test was used to determine statistical association. RESULTS: 269 cases were detected (21.2% confirmed, 50.2% clinically probable and 28.6% suspected). 61.3% were treated with permethrin, 18.6% with ivermectin and 20.1% with both. 27.1% of the cases were withdrawn.There were no significant in-site differences in the study of contacts, isolation and treatment of clothing and belongings, but there were significant differences in the prescription of drugs (P <0.001), duration of treatment (P <0.001) and disinfection of the cell (P <0.001). DISCUSSION: The number of detected cases is estimated to be high, and the majority (71.4%) confirmed or clinically probable. Control measures are homogeneous, except for cell disinfection, which was conventional in 59.1%. Pharmacological treatment and its duration varied between prisons. It would be advisable to establish a protocol to standardize control measures applied to new cases in the centers of Catalonia and subsequently evaluate their efficacy.

Crusted Scabies in a Pediatric Liver Transplant Recipient on Immunosuppression.

BACKGROUND Crusted scabies is a severe skin infection resulting from hyper-infestation with the obligate parasite Sarcoptes scabiei var. hominis. In contrast to classic scabies, crusted scabies may involve as many as hundreds to millions of mites. Importantly, this condition is associated with a mortality rate of 60% in 5 years, and is more likely to develop in immunosuppressed hosts, presumably due to an impaired T-cell response against the mite. CASE REPORT We present a case of crusted scabies in a 13-year-old girl during her early post-liver transplant period receiving immunosuppression successfully treated with topical 5% permethrin. She had pruritic erythematous papules, confirmed as scabies through skin scraping. The challenge of misdiagnosis during the initial presentation is noteworthy, given atypical manifestations and more common differentials. To our knowledge, only 2 cases of crusted scabies in pediatric solid-organ transplant recipients have been reported. Despite the absence of guidelines for pediatric solid-organ transplant recipients, urgent treatment is required due to the high associated mortality rates. In our case, early treatment proved successful without any secondary bacterial infections or clinical evidence of relapse during a 6-month follow-up. CONCLUSIONS We report a case of scabies in a pediatric liver transplant recipient that was successfully treated. It is crucial to consider the diagnosis of scabies given the associated morbidity and the risk of secondary bacterial infections among other more common differentials. Notably, the response to standard anti-scabies treatment may lead to resolution without relapse in pediatric solid-organ transplant recipients.

Scabies in infants and children - a narrative review.

Scabies is a human ectoparasitosis caused by Sarcoptes scabei var. hominis. World-wide around 300 million patients are affected. Infants and children have the highest incidence rates. Poverty and overcrowding are social factors contributing to a higher risk of transmission and treatment failure. The leading symptom of the infestation is itch. Complications are bacterial infections that are responsible for mortality. Diagnosis is clinical. Non-invasive imaging technologies like dermoscopy can be used. Polymerase chain reaction (PCR) is less sensitive and specific than microscopy of skin scrapings. Treatment of choice is topical permethrin 5%. Ivermectin is the only oral drug FDA-approved for scabies. It should be used in cases non-responsive to topical therapy and in case of high number of infested patients in addition to topical therapy. Pseudo-resistance to treatment is not uncommon. New drugs are on the horizon. What is Known: • Pruritus is the leading symptom causing sleep disturbances and scratching with the risk of secondary bacterial infections. • Treatment failure is related to inappropriate application of topical drugs and asymptomatic family members. What is New: • COVID-19 pandemic and migration are contributing to an increased incidence of scabies. • New compounds to treat scabies are on the horizon.

Scratching beneath the surface: An evaluation of the management of scabies 2017-2023.

INTRODUCTION: Possible resistance to recommended treatments for scabies has emerged recently. In response to anecdotal reports of a recent increase in treatment failure with permethrin, the British Association for Sexual Health and HIV (BASHH) released a statement alerting members to this. AIMS: To examine attendances and the treatment pathways for scabies cases seen at local sexual health clinics. METHODOLOGY: A case note review of scabies attendances between January 2017 and December 2023 was conducted. Data collected included patient demographics, clinical information, and scabies treatment histories. Statistical analysis was performed. RESULTS: 143 patients attended with scabies. The number of scabies cases did not appear to increase significantly from 2017 to 2023 (p = .09). There was significant increase in median number of treatments per case per year over time (p = .013). The number of individuals needing second-line treatments increased significantly over time (p-trend < 0.001). DISCUSSION: Individuals with scabies are requiring more treatments to clear infection. Use of ivermectin has risen in the last year suggesting that second-line treatment is increasingly needed for eradication. Whilst treatment failure may be due to non-compliance with treatment and decontamination efforts for both index and contacts, the more recent change in findings could be attributed to a fall in permethrin efficacy.

The effect of educational intervention on efficacy of 1% permethrin shampoo and 4% dimeticone lotion to treat head lice infestation using propensity score matching (PSM).

BACKGROUND: Head lice are a main public health problem and the most important human ectoparasites and the use of pediculicides is the most common way to control it. One of the possible causes of treatment failure is the lack of improper application of pediculicide. The aim of this study was to assess the effect of education on efficacy of 1% permethrin or 4% dimeticone lotion to treat head lice infestation. METHODS: This quasi-experimental study included 100 individuals with head lice infestation from comprehensive urban health centers in Ardabil as the intervention group, and 400 individuals from East Azerbaijan and West Azerbaijan provinces as the control group, from April to March 2019. The data collection tools included a demographic questionnaire and an examination recording sheet, which documented the presence of adult lice or nits. Due to the inability to perform random assignment and control for numerous observed covariates, propensity score matching (PSM) was used. RESULTS: The outcome of treatment included elimination of head lice infestation on is 7, and in the case of recurrence, it was considered on days 14 and 30 after treatment. The results showed that the educational intervention program had a significant positive effect on the efficacy of both treatments. The likelihood of improvement was approximately three times greater in the intervention group compared to the control group. CONCLUSION: Participants who received the training intervention (OR = 3.29; CI 95%: 2.21-4.88) were more likely to have a successful treatment than control group. In the case of providing proper training on the use of pediculicides and observing hygiene tips to patients with pediculosis, could help to successful treatment of pediculosis.

Failure of scabies treatment: a systematic review and meta-analysis.

BACKGROUND: Treatment failure is considered to be an important factor in relation to the increase in scabies incidence over the last decade. However, the regional and temporal differences, in addition to the predictors of therapy failure, are unclear. OBJECTIVES: We aimed to conduct a systematic review of the prevalence of treatment failure in patients with scabies and investigation of associated factors. METHODS: We searched MEDLINE, EMBASE, CINAHL, Web of Science, Scopus, Global Health and the Cochrane Central Register of Controlled Trials from inception to August 2021 for randomized and quasi-randomized trials, in addition to observational studies that enrolled children or adults diagnosed with confirmed or clinical scabies treated with permethrin, ivermectin, crotamiton, benzyl benzoate, malathion, sulfur or lindane, and measured treatment failure or factors associated with treatment failure. We performed a random effects meta-analysis for all outcomes reported by at least two studies. RESULTS: A total of 147 studies were eligible for inclusion in the systematic review. The overall prevalence of treatment failure was 15.2% [95% confidence interval (CI) 12.9-17.6; I2 = 95.3%, moderate-certainty evidence] with regional differences between World Health Organization regions (P = 0.003) being highest in the Western Pacific region (26.9%, 95% CI 14.5-41.2). Oral ivermectin (11.8%, 95% CI 8.4-15.4), topical ivermectin (9.3%, 95% CI 5.1-14.3) and permethrin (10.8%, 95% CI 7.5-14.5) had relatively lower failure prevalence compared with the overall prevalence. Failure prevalence was lower in patients treated with two doses of oral ivermectin (7.1%, 95% CI 3.1-12.3) compared with those treated with one dose (15.2%, 95% CI 10.8-20.2; P = 0.021). Overall and permethrin treatment failure prevalence in the included studies (1983-2021) increased by 0.27% and 0.58% per year, respectively. Only three studies conducted a multivariable risk factor analysis; no studies assessed resistance. CONCLUSIONS: A second dose of ivermectin showed lower failure prevalence than single-dose ivermectin, which should be considered in all guidelines. The increase in treatment failure over time hints at decreasing mite susceptibility for several drugs, but reasons for failure are rarely assessed. Ideally, scabicide susceptibility testing should be implemented in future studies.

Comparison of topical permethrin 5% vs. benzyl benzoate 25% treatment in scabies: a double-blinded randomized controlled trial.

BACKGROUND: Scabies is a pruritic parasitic infestation of the skin. High-income countries have reported an increasing incidence over the last few years. Studies have indicated a reduction in the sensitivity of scabies mites to the standard treatment of choice, topical permethrin 5%. OBJECTIVES: To evaluate in a head-to-head manner the efficacy of two topical scabicides [permethrin 5% and benzyl benzoate 25% (BB)] in the treatment of scabies using the same administration modality; and to address potential confounding factors such as incorrectly performed treatment and hygiene measures. METHODS: In total, 110 patients with dermoscopy-verified scabies infestation were enrolled and randomized into two equally sized groups in a double-blinded manner. Fifty-five received topical permethrin 5% and 55 received topical BB 25%, both for daily use over a period of three consecutive days. Treatment outcome was evaluated by dermoscopy at a 3-week follow-up visit. RESULTS: Treatment resulted in a dermoscopy-verified cure rate of 27% in the permethrin group and 87% in the BB group. The tolerability and safety profile of permethrin 5% cream was excellent, while the BB emulsion produced a burning sensation in 43% of patients. CONCLUSIONS: Topical permethrin demonstrated a lack of efficacy in the majority of scabies cases, whereas BB demonstrated an excellent cure rate and reasonable tolerability. Considering the reduced sensitivity of scabies mites to permethrin 5%, our results suggest that BB is an appropriate first-line therapy in the treatment of scabies.

What's Eating You? Tropical Rat Mite (Ornithonyssus bacoti).

The tropical rat mite (Ornithonyssus bacoti) commonly infests wild and pet rodents, but they are not host specific. Bodily contact with wild or domesticated rodents is the most common source of infestation. Mites can live off many mammal hosts for a long period of time; therefore, living in quarters infested by mice can lead to mite exposure. Human infestation presents as urticarial, pruritic, cutaneous lesions that may be misdiagnosed as an arthropod bite, an infection, or contact dermatitis. Symptomatic relief of pruritus can be provided with a topical corticosteroid or antihistamine. The most effective treatment is an antiparasitic, such as permethrin cream, as well as extermination of rodents, mites, and any other pests in the patient's living space.

Detection of a knockdown mutation in the voltage-sensitive sodium channel associated with permethrin tolerance in Sarcoptes scabiei var. hominis mites.

BACKGROUND: Increasing evidence has sparked a debate on the loss of sensitivity of scabies mites to conventional permethrin therapy. Mutations in the voltage-sensitive sodium channels (VSSC) were associated with knockdown resistance (kdr) in many arthropods, but have never been identified in Sarcoptes scabiei variatio (var.) hominis mites. OBJECTIVES: To identify factors contributing to therapy failure. METHODS: Sixty-seven mites were collected from 64 scabies-infested patients in Vienna, Austria, of whom 85.9% were refractory to prior permethrin-based treatments, and genotyped for the presence of nucleotide polymorphisms in Domain II of the VSSC, known to be associated with kdr. Information regarding previous antiscabietic therapies, decontamination procedures and possible re-infestations by contacts as well as the response to re-imposed therapies were obtained. RESULTS: Sequence alignment comparisons revealed previously unidentified mutations in the coding region of Domain II of the VSSC. A novel A1663T transversion was detected in 97.0% of the mites, resulting in a non-synonymous substitution from methionine to leucine, M918L, a mutation known to confer kdr in other arthropods. In addition, a synonymous G1659A transition was identified in one mite, which otherwise showed a nucleotide sequence identical to the wild-type reference. No major inconsistencies were observed within the previous therapeutic and decontamination procedures, which could have accounted for the observed non-responsiveness to permethrin-based therapies. Subsequent cure of infestation was achieved in 65.6% of the participants, predominantly by combination therapies with topical permethrin and systemic ivermectin. However, in 14.6% of the cured cases, permethrin monotherapy sufficed for eradication of scabies, albeit in some cases prolonged exposure was necessary. CONCLUSIONS: The kdr-associated M918L mutation in the VSSC gene has now emerged in S. scabiei var. hominis mites. Hence, loss of sensitivity to permethrin due to kdr-type resistance may be more prevalent than anticipated and may be decisive for the therapy responsiveness of scabies-infested patients.

Comparative efficacy of chemical and botanical pediculicides in Thailand and 4% dimeticone against head louse, Pediculus humanus capitis.

Head louse infestations remain a global public-health concern due to increased resistance of lice to artificial pediculicides. In Thailand, there is a lack of comparative data on the current efficacy of pediculicides for treating head lice. In this study, we explored the status of botanical and toxic synthetic pediculicides with that of 4% dimeticone liquid gel for treating head lice in Thailand. The ex-vivo pediculicidal activity of various pediculicidal shampoos available at drugstores in Thailand was assessed and compared with that of 4% dimeticone liquid gel. The shampoos chosen were based on active ingredients toxic to lice (1% permethrin, 0.6% carbaryl, 0.15% Stemona root crude extract, or mixed plant extracts), whereas dimeticone acts physically on lice. We found that exposure to 4% dimeticone liquid gel following the manufacturer's instructions completely killed 100% of head lice in 15 min, whereas other pediculicide products failed to kill the great majority of head lice, whether treatment was for 10 min (resulting in 0% to 50.0% mortality) or 30 min (resulting in 17.0% to 60.0% mortality). We also extended a clinical assessment to confirm the efficacy of 1% permethrin for treating head lice in infested schoolchildren. In this clinical assessment, none of the 26 children treated with 1% permethrin shampoo achieved a cure after two applications. These results highlight that 4% dimeticone demonstrated a higher ex-vivo pediculicidal efficacy compared to both chemical and botanical pediculicides in Thailand. Conversely, 1% permethrin showed low efficacy in both laboratory and clinical assessments. Given its physical mode of action, 4% dimeticone merits consideration as an alternative treatment option for lice in Thailand, particularly in cases where treatment with toxic pediculicides has proven ineffective.

Pseudoresistance to permethrin in scabies.

Reports of permethrin resistance of Sarcoptes scabiei var. hominis are emerging. We propose that this may be pseudoresistance. The resistance is due to inadequate counselling by physicians, incorrect treatment (insufficient quantity of permethrin; too short length of treatment), and poor adherence and compliance by patients. Other reasons include single application of permethrin, suggestion to apply the drug for 6-8 hours, failed application on subungual folds, irritant contact dermatitis, in particular on genitals, for which some patients stop the treatment, and unexplainable use of permethrin in post-scabies prurigo. Thus, we believe that several cases of resistance to permethrin are actually cases of pseudoresistance.

Permethrin-treated baby wraps for the prevention of malaria in children: Protocol for a double-blind, randomized placebo-controlled controlled trial in western Uganda.

This article details the study protocol for a double-blind, randomized placebo-controlled trial to determine the effectiveness of permethrin-treated baby wraps to prevent Plasmodium falciparum malaria infection in children 6-24 months of age. Participating mother-infant dyads will be randomized to receive either a permethrin-treated or a sham-treated wrap, known locally as a "lesu." After a baseline home visit, during which time all participants will receive new long-lasting insecticidal nets, participants will attend scheduled clinic visits every two weeks for a period of 24 weeks. In the event of an acute febrile illness or other symptoms that may be consistent with malaria (e.g., poor feeding, headache, malaise), participants will be instructed to present to their respective study clinic for evaluation. The primary outcome of interest is the incidence of laboratory-confirmed, symptomatic malaria in participating children. Secondary outcomes of interest include: (1) change in children's hemoglobin levels; (2) change in children's growth parameters; (3) prevalence of asymptomatic parasitemia in children; (4) hospitalization for malaria in children; (5) change in the mother's hemoglobin level; and (6) clinical malaria in the mother. Analyses will be conducted using a modified intent-to-treat approach, with woman-infant dyads who attend one or more clinic visits analyzed according to the arm to which they were randomly assigned. This is the first use of an insecticide-treated baby wrap for prevention of malaria in children. The study began recruitment in June 2022 and is ongoing. ClinicalTrials.gov Identifier: NCT05391230, Registered 25 May 2022.

Topical permethrin may increase blacklegged tick (Ixodes scapularis) repellency but is associated with cutaneous irritation in horses.

OBJECTIVE: To evaluate the safety of repeated applications of permethrin concentrations (0% control, 1.5%, 5%, and 10%) to the necks and faces of horses and assess the efficacy and longevity of permethrin as an equine tick repellent. ANIMALS: 5 healthy adult Quarter Horses. PROCEDURES: Each treatment was applied to the neck of each horse (0.01 m2) 4 times a day, for up to 10 days. An 8-mm biopsy was taken to evaluate postexposure dermal responses. Any treatments that were not withdrawn were applied to a quadrant of the horse's face 4 times a day, for up to 5 days. For tick bioassays, a treatment was applied to 1 leg of a horse and 5 female blacklegged ticks (Ixodes scapularis) were evaluated as "repelled" or "not repelled" by the treatment. The bioassays were repeated up to 5 days, but treatment application took place only on the first day of the experiment. RESULTS: Histological results of neck biopsies indicated that more repeated exposures or higher concentrations resulted in more dermal damage. Tick bioassays showed that 5% and 10% permethrin had the greatest efficacy and longevity as a tick repellent, but the differences in tick repellency were not significant overall. CLINICAL RELEVANCE: While there was a nonsignificant trend of higher permethrin concentrations repelling more ticks with longer-lasting residual repellent effects, higher concentrations also produced greater skin damage after repeated exposures. These opposing findings emphasize the need for better tick prevention and control methods that balance safety and efficacy for the equine community.