There are millions of missing leprosy cases. This is how we find those missing people in Bangladesh

Article by Dr Abu Sufian Chowdhury

There are millions of missing leprosy cases. This is how we find those missing people in Bangladesh

Dr Abu Sufian Chowdhury
Clinical Research Coordinator
The Leprosy Mission International Bangladesh

Hidden cases are a critical barrier to achieving zero leprosy transmission

Leprosy continues to pose significant public health challenges in Bangladesh. The slow and subtle onset of symptoms, combined with the long, up to 20-year incubation period, makes it difficult to prevent its spread. Delayed diagnosis, often driven by poor healthcare access and lack of awareness, results in many leprosy cases remaining hidden, thereby exacerbating the cycle of transmission and disability.

The SIMLEP modeling study warned of millions of undiagnosed individuals with leprosy across the world, creating a significant barrier to achieving the global goal of zero leprosy transmission by 2030. Moreover, the gradual decline in specialised leprosy control activities, driven by a shift to integrated health systems and insufficient funding, has further slowed efforts to combat the disease.

Our current approach is not doing enough to find these hidden cases

In response to this challenge, several strategies have been introduced to promote early detection, which is key to reducing both the number of new cases and disability.

One crucial intervention recommended by the World Health Organization is conducting contact surveys and administering post-exposure prophylaxis (PEP) with a Single Dose of Rifampicin to at-risk individuals. However, this approach has been underused in many countries, including Bangladesh, where a lack of resources and infrastructure has hindered widespread implementation.

Additionally, there is no readily available point-of-care diagnostic test for leprosy, making early detection even more difficult (although there is hope on that horizon, as detailed in another article in this Research Magazine). As a result, active case-finding remains one of the most effective strategies for detecting hidden cases, preventing disabilities, and stopping the spread of leprosy.

If our active case finding were more effective, we would find more of the missing millions

In Bangladesh, the annual number of new cases has remained stubbornly high, with approximately 3,500 new cases, including 5 percent child cases, reported each year up to 2023. The country’s high population density, coupled with frequent internal migration, further complicates efforts to contain leprosy transmission. This underscores the need for active case-finding strategies that are integrated into the health system and which target specific high-risk populations to identify hidden cases and prevent further transmission.

In Bangladesh, four primary active case-finding methods are used (see right).

However, these efforts have been hindered by limited resources, and many of these active case finding activities are only implemented in areas where leprosy NGOs are active. Contact-based approaches, such as Household Contact and Extended Contact Surveys, are currently only conducted in areas where leprosy NGOs operate. Additionally, a cluster-based approach, targeting high-risk clusters (defined as areas with more than two leprosy cases within a 300-meter radius), is not yet in practice due to the lack of GIS data.

Moreover, special community cohorts — such as those in Madrasas/primary schools, orphanages, slums, ethnic minorities, prisons, industrial workers, riverbed communities, and enclave areas (parts of the country that are surrounded by another country) — are often overlooked in leprosy surveys. These communities are often hidden or difficult to reach, yet they present a significant opportunity for early detection.

To address this gap, the National Leprosy Program (NLP) is working to integrate individual, community, and health system-level factors into their leprosy control efforts. They will do this by conceptualising a novel, sustainable, and cost-effective early case-finding model.

A new case-finding model that has proved effective at finding missing cases

In March-May 2024, through NLP funding, TLMI-Bangladesh conducted an operational research study to assess the costs of current active case-finding methods in two endemic districts of Bangladesh.

The study evaluated targeted methods such as contact surveys, cluster-based surveys, and special community surveys for early leprosy detection. A total of 33,107 individuals were screened, uncovering 83 new leprosy cases. Notably, 65 percent of the new cases were identified through Extended Contact Surveys, which involved screening 28,480 individuals, or 86 percent of the total population screened. Special community surveys, which screened 3,528 individuals (10 percent of the total screened), detected 25 percent of the new cases.

The special community surveys proved particularly effective in identifying cases from high-risk and marginalised areas, with 71 percent of new cases found in slums, ethnic minority communities, riverbed areas, and enclaves. The remaining 29 percent were identified in institutional settings such as orphanages, prisons, and EPZs.

The highest new case detection rate was observed in special community surveys, with 871 cases per 100,000 population, followed by Household Contact surveys (621/100,000), cluster-based surveys (212/100,000), and Extended Contact Surveys (45/100,000). Child cases, a key indicator of ongoing transmission, were predominantly identified through Extended Contact Surveys (80 percent) and special community surveys (20 percent).

The special community survey was particularly cost-efficient, as it reached large, often overlooked groups in the community, thereby identifying hidden cases at a much lower cost.

The study revealed that special community surveys were the most cost-effective, with a cost per case detected of just $23, compared to $151 for Household Contact surveys, $84 for cluster-based surveys, and $64 for Extended Contact Surveys.

These new approaches are the way forward for Bangladesh

By integrating Extended Contact Surveys and special community surveys with routine Household Contact surveys in regular leprosy control programmes, Bangladesh can significantly improve case detection, enhance disease control, and make substantial progress toward elimination.

The key challenges for leprosy control remain the lack of a simple diagnostic test, effective chemoprophylaxis, and limited resources. While skin biopsies and other diagnostic methods can confirm leprosy, they are not always accessible, especially in resource-limited settings. Therefore, targeted active case-finding activities that are more cost-effective and efficiently reach at-risk populations are essential tools in the battle against leprosy. They are the way forward for leprosy control in Bangladesh.

Note: The National Leprosy Program funded the research (Project title: Cost-Effectiveness Analysis of Active, Targeted New Case Detection Methods: Early Leprosy Case Detection in Bangladesh).

Dr Abu Sufian Chowdhury served as the Principal Investigator. Dr Tanzina Islam, Deputy Program Manager of the National Leprosy Program, and Dr Rishad Choudhury Robin, National Lead for Research at The Leprosy Mission International Bangladesh, were Co-Investigators.