B) WORKSHOP REPORTS
New Tools for Diagnosis and Epidemiology
Chair： Dr. T. Gillis
Our aim for the workshop was to review the state of the art of new tools for diagnosis and epidemiology studies of leprosy and to assess their potential impact on control programs should they be implemented. We also identified those tools needing further development and testing prior to evaluating as a tool for leprosy control.
Serology to identify at-risk contacts
After several years of extensive investigation it has become apparent that serology with PGL-1 has been found useful in identifying household contacts at high risk of developing multibacillary (MB) disease. Since MB disease is potentially the most significant reservoir of M. leprae with potential for spreading the infection, workshop participants felt that control programs should begin to explore this application. A 15-minute dipstick assay for PGL-1 antibody is now available and could be used in field conditions, for example, in small-scale LEC or SAPEL programs. Important limitations of this test require that it not be applied as a mass screening tool among community contacts but as a specific test applied to "close" contacts of MB index cases. This application ensures that the test is applied economically to a small group of contacts most likely to develop disease and who potentially represent a major link in the transmission of M. leprae among the community.
Preliminary evidence suggests that aggressive antileprosy chemotherapy of PGL-1-positive household contacts can reduce the PGL-1 antibody titer while a single dose of ROM has little or no effect. Thus, aggressive prophylactic therapy of PGL-1 positive contacts has the potential to greatly reduce the force of infection in the community. The next step in this area is to define appropriate treatment interventions for this group of at-risk contacts.
Molecular test for rifampin resistance
Tests for drug susceptibility have long been needed in leprosy. We now have one such test capable of detecting mutations associated with rifampin resistance in M. leprae.
The test is based on DNA sequences found in the rpoB gene and is being tested as a survey tool in Nepal. This survey will establish the current level of rifampin resistance in the area which can be monitored in the future to determine trends in drug-resistance. Molecular studies to define the site for DDS resistance are underway but have not yet revealed the mechanism (s) of resistance. Should it turn out to be associated with mutations in the folate pathway as suspected then a molecular test could be developed obviating the need for mouse foot pad testing for drug resistance. Other antibiotic gene targets, such as gyr A and B, are being investigated as sites for resistance to the fluoroquinolones in anticipation of their use in shortening therapy for leprosy.
