Back ground: Household contacts (HHCs) of untreated multi-bacillary (MB) leprosy patients are not only a population at high risk of developing leprosy (Hansen’s disease) but also act as carriers and used as sources for transmission. Evaluation of HHCs of newly diagnosed leprosy patients is suggested for early diagnosis of leprosy and thus decreasing disease severity and reducing its transmission. However, reports on the magnitude of leprosy from contact tracing are limited in Ethiopia. Therefore, this study aimed to determine the magnitude of leprosy and M. leprae nasal colonization among HHCs of newly diagnosed patients.

Methods: A comparative cross-sectional study was conducted from July to October 2019. In this study all HHCs of previously undiagnosed leprosy patients and randomly selected healthy endemic controls were enrolled. All study subjects underwent standard physical examination. For leprosy suspected HHCs a bacteriological examination was done. Nasal colonization was evaluated for the presence of M. leprae-specific 500bp repetitive element (RLEP). A structured questionnaire was used to obtain demographic and laboratory and leprosy related clinical history. Comparisons amongst groups were carried out by Kruskal-Wallis and Chi-square tests. Statistical significance was considered at p < 0.05 in all tests.

Results: In this study, 48 HHCs of previously undiagnosed leprosy patients were evaluated for leprosy. Four new leprosy cases (co-prevalent) were confirmed, giving a detection rate of 8.3% (95%, CI = 2%, 19%); they were excluded from the HHCs study group. On PCR analysis, 5/44 (11.4%) (95% CI: 3%, 24%) HHCs and 3/15 (20%) (95% CI: 4%, 48%) untreated leprosy cases tested positive. Nasal secretion samples from all 44 healthy endemic controls tested negative by PCR. The positivity rate was significantly different among the study groups (P = 0.022) and disability grade is associated with PCR positivity (P = 0.003). However, nasal PCR positivity was not associated with the demographic characteristics of the study groups (p > 0.05).

Conclusion: This study provides evidence that HHCs of untreated leprosy patients have clinical infections and are involved in carriage of bacilli. Therefore, HHCs tracing is important to improve early diagnosis and decipher the transmission chain.