Erythema

We undertook a cross-sectional population-based study in the Western Province of the Solomon Islands during November 2014. This was undertaken in ten villages within three distinct geographical regions within the Western Province (Vona Vona Lagoon, Roviana Lagoon and Rendova, Fig 1). Dwellings in this region are typically made of local wood. Although variable in size and structure, most comprise one to two sleeping quarters for all house inhabitants.
For logistical reasons data collection was integrated with an existing project investigating clinical and serological markers of yaws [15 ], with selected villages having participating in a mass drug administration for trachoma using azithromycin, a drug that is also active against yaws.
Ethics approval for the study was obtained from the London School of Hygiene and Tropical Medicine (LSHTM Ref 6358) and the National Health Research and Ethics Committee of the Solomon Islands Ministry of Health and Medical Services (HRC14/27). Both of these committee’s approved the research study protocols and methodology.
Following permission from community leaders, a public meeting was arranged for all village members where the study procedures and objectives were explained. Written consent was obtained for all participants. Guardians provided consent for participants aged below 18 years. All community members were eligible for this study, which took place at a pre-arranged public place.
All participants were interviewed and examined by a doctor. Assessments were conducted in the local medical clinic where one existed, or an appropriate community space. The doctor was a paediatric trainee registrar who had received specific training on the diagnosis of scabies and impetigo prior to the study, in addition to 18 months of clinical experience in tropical regions of northern Australia. Clinical history was taken in a combination of English and Solomon Island Pijin. Local nursing staff assisted with translation to local dialects (Roviana and Touo) when required. Demographic information including gender, age, and number of household and bedroom inhabitants was recorded.
Examination of the skin focused on bodily regions most commonly affected by scabies and impetigo. For infants and young children, the whole body was fully examined. For older children and adults, examination of sensitive areas such as the groin, buttocks, breasts and torso was only undertaken if there was adequate privacy. All participants who had scabies clinically on history and/or physical examination were asked whether they had similar lesions in these regions. The clinical diagnosis of scabies was based on features including morphology (burrows, papules, nodules, vesicles) and body distribution of rash; presence of pruritus on history or clinical examination evidence of excoriation; contact history with individuals with a similar rash and itch; and consideration of differential diagnoses [1 (link)]. The distribution of scabies lesions was noted using nine pre-defined body regions. Following other studies in the Pacific, scabies severity was classified by the number of lesion present as mild (≤10 lesions), moderate (11–49 lesions) or severe (≥ 50 lesions or crusted scabies) [3 (link)].
Active impetigo was diagnosed on the basis of discrete papular, pustular or ulcerative lesions with associated erythema, crusting, bullae or frank pus. Inactive impetigo was diagnosed by the presence of discrete, non-confluent healed superficial skin lesions. Severity of active impetigo was classified as very mild (≤ 5 lesions), mild (6–10 lesions), moderate (11–49 lesions) or severe (≥ 50 lesions) [3 (link)]. Participants diagnosed with any condition were counselled regarding the diagnosis and provided with an information sheet and referral letter to the nearest medical clinic for treatment according to standard local protocols [16 ].

Superficial infections were defined by erythema, wound drainage, suture abscesses, and excessive warmth at the surgical site. Superficial wound dehiscence without any clinical signs of infection were not counted as infected, and if antibiotics were given, these patients were categorized as prophylactic antibiotics. Deep infections were delineated as those who required a return to the operating room for irrigation and débridement.

For the psoriasis mouse model, the dorsal skin of mice was shaved 2 days prior to the application of the topical treatment. Mice were initially anesthetised with 4% isoflurane until movement arrest was observed, then maintained with a continuous flow of 1% isoflurane in an isoflurane chamber. IMQ cream (5%) (Mingxin Pharmaceuticals, Sichuan, China), 62.5 mg, was topically applied to the shaved 2 cm × 3 cm skin portion for six consecutive days. Control mice were treated with 62.5 mg of Vaseline (Vas) as vehicle control under the same conditions. The first day of IMQ or Vas application was defined as Day 0, and mice were euthanised on Day 4 and Day 6.
For the exogenous IL-33 administration, 1 μg of recombinant murine IL-33 (PeproTech, USA, cat: 210–33) or phosphate-buffered saline (PBS; control) in a final volume of 100 μL were administered daily through intraperitoneal injection, 1 h prior to IMQ treatment.
The severity of skin inflammation was evaluated daily by two independent researchers, using the scoring system of the psoriasis severity index (PSI). This score rated erythema, scaling, and skin thickness on a scale from 0 to 4: 0—none; 1—slight; 2—moderate; 3—marked; and 4—very marked, according to previous studies [16 (link)]. A cumulative score was generated from these parameters (scale 0–12). Mice were euthanised and samples harvested for further analyses at the respective time points.