Increase in prevalence of leprosy caused by dapsone-resistant Mycobacterium leprae.

The prevalence o f secondary resistance o f Mycobacterium leprae to dapsone (among leprom atous leprosy patients treated fo r a m inim um o f 5 years) has been estimated, from sur­ veys conducted before 1976 , to be 2 .5 /1 0 0 patients at risk in Malaysia, 3 /1 0 0 in Israel, 7 /1 0 0 in Costa Rica, and at least 1 0 /1 0 0 in Ethiopia. Apparent prim ary resistance to dapsone (among patients not known to have had treatm ent) was firs t observed in the mid-1 9 7 0 s in 1 6 o f 24 patients studied in Ethiopia. Because some o f these estim ates may have been biased and because treatm ent practices in Ethiopia may not have been representative, the THELEP Program (Chem otherapy o f Leprosy com ponent o f UNDP/W orld Bank/WHO Special Program fo r Research and Training in Tropical Diseases) decided, at its inception in 1 97 6 , to sponsor in various countries carefully conducted surveys o f the prevalence o f primary and secondary dapsone-resistant leprom atous leprosy. In Novem ber 1981 , at a Scientific Meeting on Leprosy in Rangoon, Burma (sponsored by W HO W estern Pacific and Southeast Asia Regional O ffices and the THELEP and IMMLEP [Im ­ m unology o f Leprosy] Programs), estim ates o f the prevalence o f secondary dapsone resis­ tance were reported as 6 .4 /1 0 0 in Gudiyatham Taluk, South India, 4 .1 /1 0 0 in Trivellore Taluk, South India, and 3 .6 /1 0 0 in Shanghai M unicipality, China. The surveys are still in p rog­ ress, and these estim ates are though t to be minimal. Estimates o f the prevalence o f prim ary resistance to dapsone showed a marked change: 2 /6 2 (3%) in Cebu, Philippines, 7 /4 0 (18%) in Chingleput, South India, and 1 2 /3 0 (40%) in Bamako, Mali. Cases o f prim ary resistance were also reported from Gudiyatham Taluk and Jakarta, Indonesia. This high prevalence o f prim ary dapsone resistance probably results from transmission o f M. leprae by patients whose relapses due to secondary drug resistance were not recognized and w ho therefore had not been treated w ith e ffective drugs. Because o f th is prevalence o f primary and secondary dapsone resistance, it is now neces­ sary to give com bined therapy to all new leprosy pa tien ts— both leprom atous and tuberculoid. Leprom atous patients w ho have thus far been treated only w ith dapsone should probably also be given com bined therapy. Dapsone, w h ich has been the standard drug fo r contro l o f leprosy, may eventually be o f little use, even in com bination w ith more expensive and lesswell-to le rated drugs. Earlier recom m endations fo r com bined chem otherapy have not been im ­ plemented in many countries because o f expense and feasib ility problems. The W HO Study Group on Chem otherapy o f Leprosy fo r Control Programmes has recently studied relevant problem s and has recom mended com bined-drug regimens based prim arily on the in term ittent adm inistration o f rifampin. Reported by L Levy, MD, PhD, Chairman, SK Noordeen, MD, MPH, Secretary, THELEP Steering Commit­ tee, H Sansarricq, MD, WHO Leprosy Unit, Geneva.