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.

Malaria risk factor assessment using active and passive surveillance data from Aceh Besar, Indonesia, a low endemic, malaria elimination setting with Plasmodium knowlesi, Plasmodium vivax, and Plasmodium falciparum

Background

As malaria transmission declines, it becomes more geographically focused and more likely due to asymptomatic and non-falciparum infections. To inform malaria elimination planning in the context of this changing epidemiology, local assessments on the risk factors for malaria infection are necessary, yet challenging due to the low number of malaria cases.

Methods

A population-based, cross-sectional study was performed using passive and active surveillance data collected in Aceh Besar District, Indonesia from 2014 to 2015. Malaria infection was defined as symptomatic polymerase chain reaction (PCR)-confirmed infection in index cases reported from health facilities, and asymptomatic or symptomatic PCR-confirmed infection identified in reactive case detection (RACD). Potential risk factors for any infection, species-specific infection, or secondary-case detection in RACD were assessed through questionnaires and evaluated for associations.

Results

Nineteen Plasmodium knowlesi, 12 Plasmodium vivax and six Plasmodium falciparum cases were identified passively, and 1495 community members screened in RACD, of which six secondary cases were detected (one P. knowlesi, three P. vivax, and two P. falciparum, with four being asymptomatic). Compared to non-infected subjects screened in RACD, cases identified through passive or active surveillance were more likely to be male (AOR 12.5, 95 % CI 3.0–52.1), adult (AOR 14.0, 95 % CI 2.2–89.6 for age 16–45 years compared to <15 years), have visited the forest in the previous month for any reason (AOR 5.6, 95 % CI 1.3–24.2), and have a workplace near or in the forest and requiring overnight stays (AOR 7.9, 95 % CI 1.6–39.7 compared to workplace not near or in the forest). Comparing subjects with infections of different species, differences were observed in sub-district of residence and other demographic and behavioural factors. Among subjects screened in RACD, cases compared to non-cases were more likely to be febrile and reside within 100 m of the index case.

Conclusion

In this setting, risk of malaria infection in index and RACD identified cases was associated with forest exposure, particularly overnights in the forest for work. In low-transmission settings, utilization of data available through routine passive and active surveillance can support efforts to target individuals at high risk.