Reactive Case Detection for Malaria Elimination: Real-Life Experience from an Ongoing Program in Swaziland

Hugh J W Sturrock,Zulisile Zulu,Joe M Novotny,Bryan Greenhouse,Michelle S Hsiang,Sabelo Dlamini,Justin M Cohen,Simon Kunene,Roly D Gosling,Thomas Eisele

doi:10.1371/journal.pone.0063830

Abstract

As countries move towards malaria elimination, methods to identify infections among populations who do not seek treatment are required. Reactive case detection, whereby individuals living in close proximity to passively detected cases are screened and treated, is one approach being used by a number of countries including Swaziland. An outstanding issue is establishing the epidemiologically and operationally optimal screening radius around each passively detected index case. Using data collected between December 2009 and June 2012 from reactive case detection (RACD) activities in Swaziland, we evaluated the effect of screening radius and other risk factors on the probability of detecting cases by reactive case detection. Using satellite imagery, we also evaluated the household coverage achieved during reactive case detection. Over the study period, 250 cases triggered RACD, which identified a further 74 cases, showing the value of RACD over passive surveillance alone. Results suggest that the odds of detecting a case within the household of the index case were significantly higher than in neighbouring households (odds ratio (OR) 13, 95% CI 3.1–54.4). Furthermore, cases were more likely to be detected when RACD was conducted within a week of the index presenting at a health facility (OR 8.7, 95% CI 1.1–66.4) and if the index household had not been sprayed with insecticide (OR sprayed vs not sprayed 0.11, 95% CI 0.03–0.46). The large number of households missed during RACD indicates that a 1 km screening radius may be impractical in such resource limited settings such as Swaziland. Future RACD in Swaziland could be made more effective by achieving high coverage amongst individuals located near to index cases and in areas where spraying has not been conducted. As well as allowing the programme to implement RACD more rapidly, this would help to more precisely define the optimal screening radius.

Highlights

As countries move towards malaria elimination, methods to identify and treat infections among populations who do not seek treatment are required [1,2,3,4]
Using active surveillance data since the inception of reactive case detection (RACD) in Swaziland, this study examines the effect of screening radius, and other potential risk factors, on the probability of detecting rapid diagnostic test (RDT) positive individuals during RACD, in an effort to help inform the scales at which future RACD and other interventions are targeted
Reactive case detection is an important component of Swaziland’s malaria elimination campaign that allows detection of cases that would otherwise be missed by passive surveillance

Summary

Introduction

As countries move towards malaria elimination, methods to identify and treat infections among populations who do not seek treatment are required [1,2,3,4]. One form of ACD is reactive case detection (RACD), whereby ACD is restricted to individuals living in close proximity to passively detected cases [4,8]. This type of ACD takes advantage of the fact that infections are clustered spatially and temporally within transmission ‘‘hotspots’’ [9,10,11] and is being implemented widely in a number of eliminating countries including South Africa, Swaziland, Brazil and several countries in the Asia Pacific. In Peru, it was shown that the addition of RACD within a 100 m radius around households with previous history of infection yielded an incidence of confirmed malaria cases 4.3 times higher than passive case detection alone [12]

Methods

Results

Conclusion