Aim is to ensure the effectiveness of MDT for years to come.
Multidrug therapy (MDT) is the cornerstone of leprosy treatment. Thanks to MDT, the global burden of leprosy has been substantially reduced over the past two decades. Disease prevalence has declined significantly, especially in countries where leprosy has been highly endemic for decades, and along with the decline in prevalence, annual new case detection has also started to fall in some countries.
To ensure that the achievements made as a result of MDT are sustained and that it continues to be an effective treatment for many years to come, the WHO is setting up a system to monitor drug resistance in leprosy.
"Although the problem of drug resistance is presently not acute, it is important that we collect data more systematically and monitor the trend carefully so that effective measures to combat this problem can be developed," writes Dr. V. Pannikar in the Foreword to the recently published Guidelines for Global Surveillance of Drug Resistance in Leprosy.
The emergence of drug resistance poses a threat to any infectious disease intervention. Leprosy control has already experienced this in the form of dapsone resistance, dating back to the time when the drug was used as a monotherapy treatment for leprosy.
This is what led the WHO to develop multidrug therapy in 1981, working on the assumption that a combination of three drugs, taken regularly, would prevent drug resistance.
MDT uses rifampicin, clofazimine and dapsone for treatment of multibacilliary (MB) leprosy. Recent reports have indicated instances of rifampicin resistance in several endemic areas. Resistance to dapsone has been known since the late 1960s, but so far no convincing data on clofazimine resistance has been reported.
"The establishment of a network of global surveillance for drug resistance in leprosy is primarily to keep a close vigil on the drug resistance scenario at many vulnerable settings," writes Dr. Pannikar, who is the team leader of WHO's Global Leprosy Program.
In order to address the threat, the WHO has planned the following two-pronged strategy:
1. To closely monitor trends in the occurrence of relapses* among patients after completing a full course of treatment with MDT due to drug resistance, particularly to rifampicin, which is the most important component of leprosy control, and
2. To promote research on developing new drug regimens to treat patients who harbor M. leprae strains that are resistant to standard MDT drugs or patients who cannot be treated by the standard MDT regimens due to contraindications or other reasons.
To put in place the global surveillance system, health facilities will be identified as sentinel sites in selected endemic countries that have the necessary clinical, field and laboratory support systems.
"It is important that we collect data more systematically and monitor the trend carefully."
Tissue samples will be systematically collected at these sites before being transported to designated referral laboratories where tests for drug resistance will be carried out.
Surveillance will be coordinated by the WHO's Global Leprosy Program with the support and collaboration of national programs and major research institutes around the world.
The institutes have agreed to provide free-ofcost testing of samples sent to them from the sentinel sites in the endemic countries. The initiative is expected to be conducted on a routine basis and the results will be published annually in the WHO's Weekly Epidemiological Record.
Underlining the importance of containing drug resistance, the guidelines conclude: "The global burden of leprosy in many endemic countries has declined and many patients are leading normal and productive lives as a result of MDT treatment. It is important that the achievements made with MDT over the past two decades be sustained so that the disease burden is further reduced and leprosy ceases to be a dreaded disease in the community."
* A relapse is defined as the recurrence of the disease at any time after the completion of a full course of treatment with WHOrecommended MDT.