Scabies is a common infectious disease and can cause severe outbreaks if not controlled quickly. Besides personal contact history, environmental factors are also important. This study analyzed the effects of environmental climate factors on the incidence of scabies in Taiwan. We conducted a 14-year nationwide population-based study: a total of 14,883 patients with scabies infestation were enrolled. Monthly climate data were collected from Taiwan’s Central Weather Bureau, including data on temperature, relative humidity, total rainfall, total rain days, and total sunshine hours. The linear relationships between these climate factors and scabies infestations or other risk factors were examined by Pearson’s correlation analysis. Overall, the incidence of scabies was negatively correlated with temperature (γ = −0.152, p < 0.001), while being positively correlated with humidity (γ = 0.192, p < 0.001). This useful information may provide evidence for lowering humidity at nursing facilities, hospitals, and military camps with scabies infestations, which may help to reduce its spread and prevent outbreaks.

Periodontitis (PD) is an inflammatory disease characterized by gingival inflammation and resorption of alveolar bone. Impaired receptor activator of nuclear factor-kappa B ligand/osteoprotegerin (RANKL/OPG) signaling caused by enhanced production of pro-inflammatory cytokines plays an essential role in the pathogenesis of PD. Considering melatonin possesses significant anti-inflammatory property, this study aimed to determine whether prophylactic treatment with melatonin would effectively normalize RANKL/OPG signaling, depress toll-like receptor 4/myeloid differentiation factor 88 (TLR4/MyD88)-mediated pro-inflammatory cytokine activation, and successfully suppress the pathogenesis of PD. PD was induced in adult rats by placing the ligature at molar subgingival regions. Fourteen days before PD induction, 10, 50, or 100 mg/kg of melatonin was intraperitoneally injected for consecutive 28 days. Biochemical and enzyme-linked immunosorbent assay were used to detect TLR4/MyD88 activity, RANKL, OPG, interleukin 1β, interleukin 6, and tumor necrosis factor-α levels, respectively. The extent of bone loss, bone mineral intensity, and calcium intensity was further evaluated by scanning electron microscopy, micro-computed tomography, and energy-dispersive X-ray spectroscopy. Results indicated that high RANKL/OPG ratio, TLR4/MyD88 activity, and pro-inflammatory cytokine levels were detected following PD. Impaired biochemical findings paralleled well with severe bone loss and reduced calcium intensity. However, in rats pretreated with melatonin, all above parameters were successfully returned to nearly normal levels with maximal change observed in rats receiving 100 mg/kg. As prophylactic treatment with melatonin effectively normalizes RANKL/OPG signaling by depressing TLR4/MyD88-mediated pro-inflammatory cytokine production, dietary supplement with melatonin may serve as an advanced strategy to strengthen oral health to counteract PD-induced destructive damage.