Sub-clinical infection with Mycobacterium leprae in household contacts of leprosy.

870 household contacts of leprosy patients were examined for sub-clinical infection with M. leprae by smear (skin and nasal), lepromin and FLA-ABS tests. 0.6%, 3.3%, 71.5% and 14.4% of the contacts were found to be positive for skin smear, nasal smear, lepromin and FLA-ABS tests respectively. An analysis of the results revealed that 4% of the lepromin positive contacts and 3.6% of the lepromin negative contacts were positive to both FLA-ABS and skin or nasal smear.