Leprosy elimination not yet in sight

Abstract

Setbacks in disease control and eradication programmes have been grabbing the headlines lately. The 2005 World malaria report provides grim reading (page 332), and the global polio eradication programme is again in jeopardy (page 337). Another disease scheduled for elimination is leprosy. Although not fatal, leprosy is a leading cause of disability. The chronic symptoms often afflict individuals in their most productive stage of life, and therefore impose a substantial social and economic burden. Now, half way through 2005, it is clear that the target of eliminating leprosy by the end of the year will not be met. A resolution passed at the 44th World Health Assembly in 1991 committed member states to eliminate leprosy as a public-health problem by the year 2000. Elimination was defined as a reduction in prevalence to less than one case per 10 000 population. The widespread implementation of multidrug therapy provided free of charge, shorter treatment courses, and improved access to leprosy diagnosis has meant that over the past two decades the global prevalence has fallen by almost 90%, and more than 14 million patients have been cured. 113 of the 122 countries endemic for leprosy in 1985 have reached the elimination target. But leprosy remains a major public-health problem in nine countries in Africa, Asia, and Latin America. Worryingly these countries show no decline in case-detection rate, and now countries such as Tanzania have crept back onto the endemic list, having reached their elimination target in 1997. So has elimination been the most useful target to go for? Having a target has increased leprosy awareness and political commitment in endemic countries. But the use of prevalence as the main indicator of progress has been criticised. The absence of an impact on case-detection rate in endemic countries indicates that transmission is poorly understood. One problem is that patients are infectious for some time before they are detected, so they are shedding Mycobacterium leprae into the environment for several months or longer. To eliminate a disease it needs to be diagnosed quickly and easily, but leprosy patients can often present very late in their illness. Another downside of the current strategy is misunderstanding of the elimination concept by decision-makers. Many countries on reaching elimination have substantially reduced leprosy-control activities, or, as is the case in Zambia, removed them altogether. But given that the incubation period is 7–10 years, the number of cases could shoot up again without ongoing control. It would therefore be more useful to look at case-detection as a target. Detecting cases early and treating them quickly would lower the deformity rate. Although case detection would present a much bigger challenge than the current approach, it would be a more clinically meaningful one. Relations between WHO and the non-governmental organisations in leprosy control have never run smoothly. The former has been concerned with the public-health control of leprosy, whereas the latter focus on rehabilitation of people with complications and disabilities. But there are signs now that both groups agree that providing quality, sustainable leprosy services is the way forward. Integrating leprosy services within the primary health-care system has begun already. But in countries such as Ethiopia integration has taken place faster than the capacity of the health system allowed. Staff have not been sufficiently trained and are sometimes over burdened, so quality of treatment and care of leprosy patients has been compromised. Therefore existing programmes should not be abandoned until proper support and training for integration are delivered. Leprosy research funding has also suffered as a result of the elimination notion. Questions regarding infectiousness, transmission, and how nerve damage occurs need resolving. New drugs to treat immune complications and an early diagnostic test would also be useful. Leprosy figures might fall in the next 4–5 years because of under-reporting and under diagnosis. But in another 10 years we could be faced with an increasing number of patients with deformities, which will, sadly, mean re-inventing leprosy programmes. One only needs to look at the parallels with malaria and tuberculosis, where once ridding the world of these diseases seemed a real possibility, only for them to re-emerge because control activities were not sustained. One thing is clear, leprosy cannot be judged as a disease of the past. Control measures will be required for at least another 15 years for the goals achieved by elimination to be maintained.