Global leprosy (Hansen disease) update 2023: Elimination of leprosy disease is possible – Time to act!

Commentary: Dr Paul Saunderson

The WHO Global Leprosy Programme has published the Global Leprosy Update for 2023, available on the WHO website. The report focuses on the new Leprosy Elimination Framework, published during 2023. The Framework consists of three distinct phases, which are easily described and understood, and appear to be scientifically robust.  As long as the data are available, it is not difficult to see where any particular area (be it a country or a sub-national region), sits in the Elimination Framework.  This Framework makes it easy to target our activities, so it is indeed time to act!

The first phase ends when the transmission of M leprae in that area has ceased – now defined as having registered no child cases of leprosy (under 15 years of age) for at least five years.  An Excel-based tool, known as the Leprosy Elimination Monitoring Tool (LEMT), allows data to be recorded for each sub-national area (for example, each district), each year. The LEMT automatically classifies the concerned areas into the appropriate, colour-coded elimination phases according to the Leprosy Elimination Framework. It thus displays progress towards the elimination targets over time, for each district, and in aggregate, for the country as a whole.

One of the numbers in the report that struck me as particularly significant was that of 184 countries reporting, 110 reported zero child cases (see p 505 of the report), and according to the tabulated data, another 38 countries reported fewer than 10 child cases.  This suggests that 148/184 (80%) of countries that reported are making good progress towards the end of this first phase of leprosy elimination.  Every country and every sub-national area is different and on a different trajectory, but once data-points are plotted over a number of years, any progress can be seen, and areas with slower progress can be identified and assisted.

A second number (on page 508) was much more worrying.  It is stated that of the 182,815 new leprosy cases reported, only 14,908 (8%) were detected through active case finding.  Clearly this is not necessarily a very accurate figure, as some programs do not report it, but it may help to remind us that active case-finding (at present contact examination is the favoured method, and skin camps have proven very effective in many communities in Africa) is the key activity in any effort to ‘end leprosy’.  It is also a common finding that when active case-finding is done rigorously in any particular endemic area, the number of new cases identified is usually higher than expected, suggesting a significant under-reporting of new cases globally.  If post-exposure prophylaxis (PEP) is to be given, as recommended by WHO, it is easily carried out in the context of contact examination or a skin camp.  It is unfortunate that the WHO update does not yet include more detailed statistics of active case finding and of PEP administration, as these are currently optional reporting fields.

Even people who do not favour PEP usually emphasize active case finding, which can be very successful over time, if carried out rigorously (for example, the decades long programme in Malawi reported by Prof Paul Fine and colleagues¹). Another important reason to emphasize contact examination is that, by identifying new cases early, a significant decrease in disability can be achieved.

In summary, the good news is that many countries and many sub-national regions are making good progress towards zero leprosy.  The main challenge, however, is to greatly expand active case-finding – particularly through contact tracing – in the remaining endemic areas, especially in the 23 WHO priority countries. This is a time-consuming and costly exercise, but it can be made much more efficient by carefully targeting hotspot areas. These can be identified by various mapping techniques and the LEMT is one of the best tools available, with its own built in mapping function (in preparation).  While the new WHO paradigm gives us a framework for action, active case finding should be the main focus of our activities, ideally supplemented with PEP.

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¹ LEP – KPS Team; The epidemiology of leprosy in Karonga District, northern Malawi 1973–2023: An analysis of leprosy’s distribution, risk factors, control and decline in rural Africa; Leprosy Review. 2024; 95; 1; 7-84; DOI: 10.47276/lr.95.1.7