An approach to understanding the transmission of Mycobacterium leprae using molecular and immunological methods: results from the MILEP2 study.

Background: The current strategy for leprosy control using case detection and treatment has greatly reduced the prevalence of leprosy, but has had no demonstrable effect on interrupting transmission.

Methods: Three leprosy endemic communities in India were recruited, examined, and followed up sequentially over 2 yrs using nasal swabs and saliva collections. The nasal swabs were tested by polymerase chain reaction for the presence of M. leprae and the saliva was assayed for anti-M. leprae IgA.

Findings: Only 1.6% of 2552 nasal swabs were PCR positive, and 68% of saliva samples were positive for ML-IgA. BCG and household contact status was associated with the mucosal immune response, but not with PCR positivity. PCR positivity did not persist and most PCR positive results were in the wet season.

Interpretation: The findings contribute to our understanding of the epidemiology of M. leprae and the possible periods of greatest likelihood of exposure and transmission.