Elimination of leprosy as a public health problem: progress and prospects.

Update /Le point Elimination of leprosy as a public health problem: progress and prospects* S.K. Noordeen1 Leprosy is still an important problem in about 80 countries of Asia, Africa and Latin America, some 2.4 million persons being estimated to have the disease in 1994. The WHO-recommended standard multidrug therapy (MDT) was introduced in the 1980s and has been shown to be effective in combating the disease. Experiences based on many thousands of patients treated with MDT over the past decade indicate extremely low relapse rates (cumulative relapse rates around 1%). By the end of 1993, some 5.6 million patients had been cured, and the global cumulative MDT coverage of registered patients had reached 89%. The number of registered cases fell from 5.4 million in 1985 to 1.7 million in 1994. The significant progress made in leprosy control enabled the World Health Assembly in 1991 to set a goal for eliminating leprosy as a public health problem by the year 2000. One important epidemiologi- cal factor is that leprosy is very unevenly distributed: 80% of the problem is confined to only five coun- tries and 92% to just 25 countries. The elimination strategy envisages identifying and treating with MDT a total of about 5 million cases from 1994 to the year 2000. The cost of dealing with these cases has been estimated at US$ 420 million, including US$ 150 million for the drugs. For ages leprosy remained a disease without hope, and leprosy control was a series of frustrations. The situation has now changed dramatically after the introduction of multidrug therapy (MDT) in the 1980s and the subsequent drastic reductions in prev- alence. It was this success with MDT that led WHO in 1991 to set the goal for eliminating leprosy as a public health problem by the year 2000, elimination being defined as a level of prevalence <1 case per 10 000 population. The disease burden Leprosy occurs in significant numbers in about 80 countries or territories of Asia, Africa, and Latin America. Estimates for December 1993 indicate a global total of 2.4 million cases as against 10 to 12 million in the 1970s. Approximately 1.7 million were on treatment registers by mid-1993 as against * A French translation of this article will appear in a later issue of the Bulletin. I Chief, Leprosy Unit, World Health Organization, 1211 Geneva 27, Switzerland. Requests for reprints should be sent to this address. Reprint No. 5559 5.4 million in 1985. About 600 000 new cases are being detected annually and about 2400 million people live in countries with a leprosy prevalence of >1 per 10 000. In all, between two and three million individuals are visibly disabled as a result of leprosy. Of all the communicable diseases, leprosy is most important for its potential to cause permanent and progressive physical disability. The disease, par- ticularly the visible disability, contributes to intense social stigma and social discrimination of patients. It is estimated that the expected healthy years of life lost is about 3.4 years per patient (1). Leprosy is a very unevenly distributed disease between and within countries. Five countries contrib- ute to 80% of the global burden and 25 countries contribute to 92%. Table 1 and Fig. 1 show the dis- tribution, by regions and countries. Multidrug therapy Until 1980, domiciliary treatment of patients with dapsone was, to a limited degree, successful in lepro- sy control in well-organized programmes. However, owing to the widespread resistance of Mycobacteri- um leprae to dapsone, treatment became increasing- ly ineffective. In addition, the long-term and often life-long treatment that was required with this drug Bulletin of the World Health Organization, 1995, 73 (1): 1-6 © World Health Organization 1995 1 S.K. Noordeen Table 1: Prevalence of registered cases and coverage with multidrug therapy, by WHO region Registered Prevalence MDT Cured Cumulative WHO Region cases per 10 000 coverage (%) with MDT coverage (%) Africa 149 212 2.78 67.22 262 859 88.13 Americas 267 196 3.55 39.15 55 251 49.58 South-East Asia 1 170 763 8.47 53.95 5 137 485 91.45 Europe 4 927 0.06 47.49 2 134 63.36 Eastern Mediterannean 22 575 0.53 90.43 29 907 95.88 Western Pacific 56 824 0.35 92.34 171 354 98.09 Total 1 671 497 3.01 54.55 5 658 990 89.64 led to poor patient compliance and ineffective dis- ease control in general. This period of failure and frustration, however, changed dramatically with the introduction of a greatly improved treatment strategy through the combination of drugs or MDT, the stan- dard regimens of which were first recommended by a WHO Study Group in 1981 (2). MDT was very well accepted by the national health services and leprosy patients themselves and this was due to: (a) the absence of treatment failures attributable to drug resistance; (b) the very low Fig. 1. Distribution and prevalence of leprosy in the world. relapse rates following completion of treatment (mean cumulative risk of 1% over 9 years of follow- up); (c) the fixed and relatively short duration of treatment; and (d) the very low frequencies of side- effects which contributed to better treatment compli- ance. The introduction of MDT has also contributed to other improvements in the organization of leprosy control. For instance, reviewing leprosy registers and deleting inactive cases have contributed considerably to case-load reductions in certain countries. In sever- 0_@°-0 a 0 0 * 0 a 0 0 0CC The designations employed and the presentation of material on this mfsp do not imply the expression of any opinion whataoever on the part of the World Health Organization concening the lgal status of any country territory. city or area or of its authoribes, or concerning the delimitation of its frontiers or boundares. Dotted lines represent approximate border lines for which there may not yet be full agreement. WHO Bulletin OMS. Vol 73 19952 Elimination of leprosy al others it was possible to implement MDT, even where the basic health services were not very well organized. Although MDT does not have any direct impact on deformities in those patients who are already deformed, it has contributed substantially to the pre- vention of deformities through early self-reporting and early cure. With the increasing application of MDT and the large number of patients being dis- charged from registers, some programmes are increasing their focus on deformed patients, whether under treatment or already cured. Following widespread introduction of MDT in the 1980s, leprosy prevalence has been greatly reduced. By the end of 1993 (10 years after its intro- duction) about 5.6 million patients had been cured and the global prevalence had been reduced by about 68%. Table 2 gives details of MDT implementation in the top 25 endemic countries. Elimination of leprosy as a public health problem The WHO recommendation on MDT is recognized today as a major technological improvement in leprosy control. In the absence of any primary pre- ventive approach such as an effective vaccine, MDT remains the mainstay for leprosy control. Because the leprosy patient is the only epidemiologically significant reservoir of infection, there is every hope that through early diagnosis and effective treatment, the transmission of the disease could virtually be stopped over a period of time. Experience in many countries in the past 10 years has demonstrated convincingly that a well-organized leprosy control programme can reduce the prevalence of registered cases up to tenfold within a period of five years. In several countries MDT has provided govern- ments with the opportunity to increase the priority Table 2: Magnitude of the leprosy problem in the top 25 endemic countriesa Countries Registered Prevalence Patients MDT Completed Cumulative MDT and areas cases per 10 0oOb on MDT coverage (%) MDT coverage (%) India Brazil Bangladesh Indonesia Myanmar Nigeria Philippines Nepal Sudan Zaire Ethiopia Mozambique Guinea Colombia C6te d'lvoire Viet Nam Mali Madagascar Chad Mexico Cambodia Niger Thailand Egypt Iran Total 995 285 223 539 22 334 70 961 56 410 33 196 15 441 17 756 4 579 8 190 15 673 12 838 4 811 6 628 3 762 8 018 8 000 5 369 7 468 8 938 2 038 6 563 5 917 3 338 2 627 11.34 14.30 1.83 3.71 12.98 3.75 2.32 8.42 1.71 2.16 3.00 7.77 7.63 1.95 2.90 1.13 8.15 4.19 12.43 0.97 2.27 7.96 1.04 0.61 0.46 516 413 72 694 15 079 45 831 31 646 20 887 15 441 14 700 4 579 5 460 12 059 5 413 4 811 6 628 3 602 6 979 4 800 5 369 3 967 6 187 2 038 1 690 5 905 3 338 2 627 51.20 32.52 67.52 64.59 56.10 62.92 100.00 82.79 100.00 66.67 76.94 42.16 100.00 100.00 95.75 87.04 60.00 100.00 53.12 69.22 100.00 25.75 99.80 100.00 100.00 4 557 126 23 008 43 046 77 933 101 998 2 251 66 941 26 370 2 478 41 957 50 578 533 22 510 1 668 16 163 23 284 3 279 9 118 3 405 4 417 3 686 1 662 38 696 16 024 1 549 679 7.15 818 143 52.79 5 404 101 91.77 38.82 88.90 83.12 84.37 65.27 100.00 93.07 100.00 94.56 94.54 44.47 100.00 100.00 99.20 96.68 71.63 100.00 67.80 79.40 100.00 40.75 99.97 100.00 89.48 a Ranking of countries is based on the number of estimated cases. b Using the 1993 mid-year population data from Demographic data for health situation assessment and pro- jections (unpublished document WHO/HST/GSP/93.2, 1993). WHO Bulletin OMS. Vol 73 1995 3 S.K. Noordeen given to leprosy control and to strengthen their polit- ical commitment for leprosy. MDT has also made possible the strengthening of health services for lep- rosy control in many countries. Its cost-effectiveness and the results obtained have contributed to increas- ed resources, including those from bilateral and international agencies as well as NGOs, both nation- al and international, in a number of leprosy-endemic countries. Because of the optimism that developed as a result of MDT, the Forty-fourth World Health Assembly in May 1991 adopted a resolution to elim- inate leprosy as a public health problem by the year 2000; elimination was defined as attaining a preva- lence level of <1 case per 10 000 population. This resolution declared WHO's commitment to global elimination, and urged the countries to increase their political commitment to this goal. By establishing a target for the year 2000, the World Health Assem- bly (WHA) drew attention to the effectiveness of the available treatment technology, the need for leprosy-endemic countries and donor agencies to stop regarding leprosy as a permanent problem and to re- double their efforts towards controlling the disease, and to accept leprosy as simply another health prob- lem with a clear solution. It is obvious that elimination is not total eradica- tion of the disease. We are willing to accept a small residual problem in the hope that, when such low lev- els are reached, the transmission of infection will be so minimal that the disease will eventually die out. Although the WHA resolution refers to global elimi- nation, it is implicit that it should also occur at regional and national levels. Strategy for global elimination Following the adoption of the WHA resolution, stra- tegies to attain elimination have been discussed at national and regional levels, and based on these WHO has developed a global strategy for elimina- ting leprosy as a public health problem. A global strategy is essential if the envisaged goal is to be achieved. The time-limited nature of the goal war- rants constant review of the progress being made and the application of flexible approaches, particularly in areas where special problems are faced. A global plan of action to implement the strategy has also been developed by WHO. Since leprosy is very unevenly distributed be- tween and within countries, the ability of the health services to implement disease control vary widely in the different endemic countries. The elimination stra- tegy will have to take into account such variations and be adaptable to suit specific needs. Stratification, target-setting, and working towards the targets are essential aspects of the elimination strategy. Capacity-building, preparation of action plans, and resource mobilization are other important elements of the strategy. If the intensification of leprosy control activities through MDT continues as planned, the figures for estimated prevalence, registered prevalence, estimat- ed incidence and case-detection will converge at low levels as we near the year 2000 (Fig. 2). In terms of stratification, the following will be the most important factors to be considered: A. Size and intensity of the problem: Registered prevalence: absolute number and rate Estimated prevalence: absolute number and rate Annual case-detection: absolute number and rate Estimated incidence: absolute number and rate. B. Delivety of leprosy control services: MDT coverage: current and cumulative rates - Accessibility and type of health services Social factors, including community awareness, for early detection of cases. Allocation of resources and setting priorities at regional and global levels, and the development of strategies and target-setting at country level could be based on the above considerations. A stratification based on the most significant epidemiological and operational indicators is a help for setting priorities. The elimination strategy also calls for the set- ting-up of intermediate targets and their constant monitoring. Short-term target-setting will relate mainly to disease reduction through cure of patients with MDT and the consequent reduction in preva- lence, while target-setting for the latter phases of Fig. 2. Global elimination of leprosy: targets and expec- tations, 1993-2000. 3.5 3 C2.5 0 *g 2 0 1.5 cn 1 0.5 v 1993 1994 1995 1996 1997 1998 1999 2000 Year WHO Bulletin OMS. Vol 73 1995 Estimated - Registered - Incidence .* Detection .......... - 4 Elimination of leprosy MDT implementation will, in addition, be aimed at disease reduction through the occurrence of fewer new cases owing to reduced transmission of infec- tion. For the elimination strategy to be effective it needs to be simple enough to be widely implemented and flexible enough to be adapted to the rapidly changing needs of the disease and disease control. The basic strategy of stratification and targeting apply to all levels-global, regional, national and subnational. At the global level, the top 25 countries contributing to 92% of all cases will be the major target. Even among these, certain countries with very large case-loads and high incidence will need inten- sive efforts if elimination is to be achieved. While reducing the prevalence will be directly proportional to MDT efforts, reducing the incidence will depend on other additional factors. Thus, countries which have an annual incidence rate of <1 case per 10 000 population and a prevalence rate of several times that figure will, by administering MDT to all the existing leprosy cases, achieve the elimination goal much earlier and more easily than countries which have annual incidence rates considerably >1 per 10 000 population. The elimination strategy envisages substantial additional resources up to the year 2000. Major costs will revolve around MDT and other activities includ- ing case-detection, training, supervision, referral, and monitoring and evaluation; these costs vary greatly according to the prevalence and health service devel- opment in the country. Assuming that between 1994 and 2000 about five million patients will have to be treated with MDT, the estimated additional costs would amount to about US$ 420 million, of which about US$ 150 million will be needed for drugs. Future challenges It is clear that the treatment of leprosy through MDT is working very well with very high cure rates and very low rates of relapse. So far, there has been no significant problem with drug resistance. However, with increasing use of MDT by different sectors, some of them employing injudicious drug combina- tions, drug resistance may emerge as a problem in the future, and better and newer MDTs may become necessary. Currently, more than one new combina- tion of drugs is under clinical trial, providing opti- mism that better MDT regimens capable of dealing with drug resistance problems and of reducing the period of treatment will become available in the future. Although MDT has contributed to a rapid reduc- tion in prevalence, its positive impact on case detec- tion and incidence has been limited and in many areas not easily visible, at least during the first five years of its implementation. This appears to be due largely to the long incubation period of leprosy as well as operational factors such as vigorous case- finding activities. However, it is expected that over a period of 5-10 years of implementation, MDT will have an impact on incidence rates. This is already seen in a number of countries, e.g., Thailand (Fig. 3). However, it is not yet clear how soon such an impact will be seen in areas where the current intensity of the disease is very high. As the goal nears, tools and methods for moni- toring and evaluating very low prevalence situations will be important in order to certify whether or not elimination levels have been achieved. Furthermore, since elimination is not eradication, different strate- gies will have to be developed to deal with the very small number of incident cases and the backlog of already deformed individuals. Maintaining skills and facilities for diagnosing and treating leprosy will be particularly important. While any resurgence after reaching very low levels is not expected to be a sig- nificant problem, it is important to maintain epidemi- ological surveillance. Conclusions Eliminating leprosy as a public health problem calls for coordinated efforts by all interested parties, keep- ing in mind the specific mandates of the vari- ous agencies interested in leprosy control with their relative advantages and special interests, and the amount and nature of the resources available to them. Ongoing coordination efforts should be further strengthened so that the available resources are util- ized optimally. Given the available and anticipated technologies and strategies for leprosy control, and more recently Fig. 3. Leprosy: trends in Thailand, 1974-94. 25 1984 1989 1994 Year WHO 94807 WHO Bulletin OMS. Vol 73 1995 5 S.K. Noordeen the political will and the opportunities to raise resources through various mechanisms, the elimina- tion of leprosy as a public health problem by the year 2000 - in spite of some difficulties in a small num- ber of countries - has become a real possibility. The attainment of this goal will not come easily and requires intensified efforts by all concemed, in terms of both action and mobilization of adequate resourc- es. Such intensification is important, particularly dur- ing the next few years. For the leprosy-endemic countries, it is an important opportunity to solve a major public health problem, which should not be missed. References 1. Jamison DT et al. Disease control priorities in developing countries. New York, Oxford University Press (for World Bank), 1993. 2. Chemotherapy of leprosy for control programmes. Report of a WHO Study Group. Geneva, World Health Organization, 1982 (WHO Technical Report Series, No. 675). 6 WHO Bulletin OMS. Vol 73 1995