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Epidemiology of leprosy identified through active case detection in six districts of Nepal

Background Nepal has achieved and sustained elimination of leprosy as a public health problem since 2009, but 17 districts and 3 provinces have yet to eliminate the disease. Pediatric cases and grade-2 disabilities (G2D) indicate recent transmission and late diagnosis respectively, which necessitate active and early case detection. This operational research was performed to identify approaches best suited for early case detection, determine community-based leprosy epidemiology, and identify hidden leprosy cases early and respond with prompt treatment. Methods Active case detection was performed by: house-to-house visits among vulnerable populations ( n= 26,469), contact examination and tracing ( n= 7,608) and screening prison populations ( n= 4,428) in Siraha, Bardiya, Rautahat, Banke, Lalitpur and Kathmandu districts of Nepal. Results New case detection rates were highest for contact tracing (250), followed by house-to-house visits (102) and prison screening (45) per 100,000 population screened. However, cost per case identified was cheapest for house-to-house visits (Nepalese rupee (NPR) 76,500/case), then contact tracing (NPR90,286/case) and prison screening (NPR298,300/case). House-to-house and contact tracing case paucibacillary/multibacillary (PB:MB) ratios were 59:41 and 68:32; female/male ratios 63:37 and 57:43; pediatric cases 11% in both approaches; and G2D 11% and 5% respectively. Developing leprosy was similar among household and neighbor contacts (Odds ratios (OR)=1.4, 95% confidence interval (CI), 0.24-5.85) and for contacts of MB versus PB cases ( OR= 0.7, 0.26-2.0). Attack rates were similar among household contacts of MB cases (0.32%, 0.07-0.94%) and PB cases (0.13%, 0.03-0.73) and neighbor contacts of MB cases (0.23%, 0.1-0.46) and PB cases (0.48%, 0.19-0.98). BCG vaccination with scar presence had a significant protective effect against leprosy ( OR= 0.42, 0.22-0.81). Conclusions The most effective case identification approach here is contact tracing, followed by house-to-house visits in vulnerable populations and screening in prisons. The findings suggest hidden cases, recent transmission, and late diagnosis in the community exist and highlight the importance of early case detection.