A Laboratory-Based Surveillance System for Wuchereria bancrofti in Togo: A Practical Model for Resource-Poor Settings

Abstract

One goal of the Global Program to Eliminate Lymphatic Filariasis (GAELF) is interruption of disease transmission through annual mass drug administration (MDA) in areas where LF prevalence is greater than 1%. After MDAs are completed, the World Health Organization (WHO) recommends a period of passive surveillance before final certification of LF elimination is achieved. Guidelines for such a surveillance system have yet to be developed. This paper describes a surveillance system launched in Togo in 2006. The system uses existing laboratories with technicians on call at night who, among other activities, prepare nocturnal thick blood smears for malaria diagnosis that can also be used for LF diagnosis. During its first 2 years (2006–2007), the system provided geographically disperse sampling nationwide, and 1 of 750 people residing in Togo was tested. Over the same period, the system detected two cases of LF, both from areas previously considered non-endemic. This system could be a cost-effective, sustainable model for WHO-mandated passive surveillance after cessation of MDA.

Evidence for Stopping Mass Drug Administration for Lymphatic Filariasis in Some, But Not All Local Government Areas of Plateau and Nasarawa States, Nigeria

“…Several false ICT positives occurred among children in stop MDA surveys in Togo that were implemented around the same time as our surveys. 24 Those results conflict with historical performance of the filarial antigen-based diagnostics in adults. 19 In contrast to the methodology of our populationbased surveys, in the follow-up assessments in baseline sites, all adults who were ICT positive were checked for mf; no mf positives were found.…”

Ongoing Surveillance for Lymphatic Filariasis in Togo: Assessment of Alternatives and Nationwide Reassessment of Transmission Status

“…The geographic catchment area of the laboratory-based surveillance system was charted by plotting the village of residence for each patient tested in 2006 and 2007. 7 Coordinates for each village were obtained from a Ministry of Health (MOH) global positioning system (GPS) database and prior neglected tropical diseases (NTD) mapping studies (unpublished data). In addition, the *Address correspondence to Els Mathieu, Center for Global Health, Centers for Disease Control and Prevention.…”

“…The laboratory-based LF surveillance system in Togo has previously been described 7 and relies on detection of circulating microfilariae in thick blood smears drawn between 10:00 PM and 2:00 AM from patients being evaluated (usually to rule out malaria) at district hospitals (or their equivalent) throughout the country. Areas undersampled by the laboratory-based surveillance system were identified through review of the catchment area map (Figure 2A).…”

“…6 A nationwide laboratory-based LF surveillance system, developed in cooperation with the US Centers for Disease Control and Prevention (CDC), covering all 35 districts and designed to be sustainable in resource-poor settings was implemented in 2006 and has been described in detail in the work by Mathieu and others. 7 The technicians in this laboratory-based surveillance system review nocturnal malarial thick blood smears collected from patients at district hospitals (or equivalent inpatient facilities) throughout the country for the presence of microfilariae. During the first 2 years of surveillance, the system detected two cases of positive microfilaremia among 8,050 persons whose nocturnal thick blood smears were reported to the surveillance system.…”

“…During the first 2 years of surveillance, the system detected two cases of positive microfilaremia among 8,050 persons whose nocturnal thick blood smears were reported to the surveillance system. 7 At the request of the National Program to Eliminate LF in Togo (NPELF), the CDC provided an evaluation of the first 2 years of the surveillance system. This paper describes the evaluation, which included assessment of possible alternative ways to implement LF surveillance in Togo, and reports on the implementation of suggested improvements.…”