Preventing leprosy with retrospective active case finding combined with single-dose rifampicin for contacts in a low endemic setting: results of the Leprosy Post-Exposure Prophylaxis program in Cambodia.

Post-exposure prophylaxis (PEP) with single-dose rifampicin (SDR) reduces the risk of developing leprosy among contacts of leprosy patients. Most evidence for the feasibility of the intervention is from highly endemic settings while low-endemic areas present unique challenges including reduced awareness of the disease among the population and in the health system, and the only sporadic occurrence of cases which together make defining any type of routine process challenging. We complemented the retrospective active case finding (RACF) approach with SDR administration to eligible contacts, and piloted the intervention across 31 operational districts in Cambodia. The aim was to demonstrate the feasibility of improving early case detection and administering SDR in a low endemic setting. The intervention focused on leprosy patients diagnosed since 2011 and was implemented between October 2016 - September 2019. The "drives" approach was employed to trace contacts: a trained team systematically contacted all eligible cases in a district, traced and screened contacts, and administered SDR. A total of 555 index patients were traced by the drive team, and 10,410 contacts in their household and 5 immediate neighbor houses listed. Among these contacts, 72.0% could be screened while most others were absent on the screening day. A total of 33 new leprosy cases were diagnosed and 6189 contacts received SDR (82.6% of the screened contacts). Sixty-one contacts refused SDR administration. We conclude that integrating PEP with SDR in RACF campaigns is feasible, and that this approach is appropriate in low resource and low endemic settings. Over time, evidence on whether or not the approach reduced leprosy transmission in Cambodia, may become clear.

Retrospective active case finding in Cambodia: An innovative approach to leprosy control in a low-endemic country.

Currently, leprosy control relies on the clinical diagnosis of leprosy and the subsequent administration of multidrug therapy (MDT). However, many health workers are not familiar with the cardinal signs of leprosy, particularly in low-endemic settings including Cambodia. In response, a new approach to early diagnosis was developed in the country, namely retrospective active case finding (RACF) through small mobile teams. In the frame of RACF, previously diagnosed leprosy patients are traced and their contacts screened through "drives". According to the available records, 984 of the 1,463 (67.3%) index patients diagnosed between 2001 and 2010 and registered in the national leprosy database were successfully traced in the period 2012-2015. Migration (8.4%), death (6.7%), operational issues (1.6%) and unidentified other issues (16.0%) were the main reasons for non-traceability. A total of 17,134 contacts of traced index patients (average: 2.2 household members and 15.2 neighbors) and another 7,469 contacts of the untraced index patients could be screened. Among them, 264 new leprosy patients were diagnosed. In the same period, 1,097 patients were diagnosed through the routine passive case detection system. No change was observed in the relation between the rate at which new patients were identified and the number of years since the diagnosis of the index patient. Similar to leprosy patients diagnosed through passive case detection, the leprosy patients detected through RACF were predominantly adult males. However, the fraction of PB leprosy patients was higher among the patients diagnosed through RACF, suggesting relatively earlier diagnosis. It appears that RACF is a feasible option and effective in detecting new leprosy patients among contacts of previously registered patients. However, a well-maintained national leprosy database is essential for successful contact tracing. Hence, passive case detection in the frame of routine leprosy surveillance is a precondition for efficient RACF as the two systems are mutually enhancing. Together, the two approaches may offer an interesting option for countries with low numbers of leprosy patients but evidence of ongoing transmission. The impact on leprosy transmission could be further increased by the administration of single dose rifampicin as post-exposure prophylaxis to eligible contacts.