High rate of Mycobacterium leprae infection and nasal colonization among household contacts of previously undiagnosed leprosy patients

Objective This study examined the magnitude of M. leprae infection and nasal colonization among household contacts (HHCs) of newly diagnosed leprosy patients. Methods A community-based cross sectional study was conducted from July to October 2019 in Fedis district, eastern Ethiopia. This study involved all healthy HHCs of previously undiagnosed leprosy patients and equal numbers of randomly selected healthy endemic controls. All study participants underwent a standard physical examination. For leprosy-suspected HHCs a bacteriological examination was done. Nasal colonization among HHCs and endemic controls was evaluated for the presence of M. leprae-specific 500 bp repetitive elements (RLEP) using PCR. A structured questionnaire was used to obtain demographic, laboratory and leprosy-related clinical history. 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.