Targeting Asymptomatic Malaria Infections: Active Surveillance in Control and Elimination

Abstract

Hugh Sturrock and colleagues discuss the role of active case detection in low malaria transmission settings. They argue that the evidence for its effectiveness is sparse and that targeted mass drug administration should be evaluated as an alternative or addition to active case detection. Please see later in the article for the Editors' Summary

High Levels of Asymptomatic and Subpatent Plasmodium falciparum Parasite Carriage at Health Facilities in an Area of Heterogeneous Malaria Transmission Intensity in the Kenyan Highlands

“…1,2 Most malaria surveillance systems, including the system in Kenya, are predicated on passive detection of cases at health facilities using either clinical diagnosis alone or clinical diagnosis with parasitological confirmation by microscopy or rapid diagnostic tests (RDTs). [3][4][5][6] However, estimates of malaria burden from passive case detection data are subject to a number of potential biases that can vary considerably between health facilities, including the occurrence of nonmalarial fevers, variations in accessibility of health services, willingness to pay any ancillary costs, and diagnostic test used.…”

Towards the implementation of malaria elimination policy in South Africa: the stakeholders’ perspectives

“…While there is no denial that over the years malaria morbidity and mortality have been drastically reduced in South Africa [13,15] and elsewhere in the world [1,2], informants shared mixed views as to what led to these reductions. Some claimed that these achievements were as a result of effective malaria control interventions [5,13,35]. Others attributed the successes to changes in the climate, as implicated in other studies [1].…”

Capture and Ligation Probe-PCR (CLIP-PCR) for Molecular Screening, with Application to Active Malaria Surveillance for Elimination

“…To achieve elimination and prevent resurgence, surveillance systems must be able to effectively interrupt transmission by detecting all possible malaria infections in the area in a timely manner (2 ). In low-endemic areas, the most widely adopted approach of surveillance is a strategy of targeted active case detection, whereby either all high-risk individuals in a community ("hotpops"), or household members, neighbors, and other contacts of passively detected cases ("hotspots"), are screened for infection and treated with rapid-response measures, including radical treatment and targeted vector control (3,4 ).…”

“…Diagnostic methods implemented in most elimination programs include microscopy and rapid diagnostic tests (RDTs), 4 both recommended by WHO (5,6 ). Although the sensitivities of these methods are generally sufficient to diagnose acute malaria cases, they have important limitations in low-endemic settings, since a substantial proportion of infections might be asymptomatic and subpatent, i.e., a density lower than the threshold needed for detection by microscopy or RDT, and these have been estimated to result in 20%-50% of all trans-mission episodes (1 ).…”

“…Positive samples will be identified within 2-3 days, and an additional day may be used for species identification by use of standard qPCR. The results are quickly fed back to the local and state monitoring agencies via networked rapid communications, followed by rapid response measures such as targeted mass drug administration (3,4 ) to prevent any onward transmission. The targeted total turnaround time can be less than a week.…”