The impact of reactive case detection on malaria transmission in Zanzibar in the presence of human mobility

Elsevier

Available online 20 October 2022, 100639

EpidemicsHighlights•

Imported infections are a key driver in the persistence of malaria in Zanzibar.

Elimination will be difficult to reach without targeting ongoing imported cases.

Presumptively treating household members of malaria cases reduces transmission.

Testing and treating neighbours of malaria cases has minimal impact on transmission.

Abstract

Malaria persists at low levels on Zanzibar despite the use of vector control and case management. We use a metapopulation model to investigate the role of human mobility in malaria persistence on Zanzibar, and the impact of reactive case detection. The model was parameterized using survey data on malaria prevalence, reactive case detection, and travel history. We find that in the absence of imported cases from mainland Tanzania, malaria would likely cease to persist on Zanzibar. We also investigate potential intervention scenarios that may lead to elimination, especially through changes to reactive case detection. While we find that some additional cases are removed by reactive case detection, a large proportion of cases are missed due to many infections having a low parasite density that go undetected by rapid diagnostic tests, a low rate of those infected with malaria seeking treatment, and a low rate of follow up at the household level of malaria cases detected at health facilities. While improvements in reactive case detection would lead to a reduction in malaria prevalence, none of the intervention scenarios tested here were sufficient to reach elimination. Imported cases need to be treated to have a substantial impact on prevalence.

Keywords

Malaria

Reactive case detection

Human mobility

Surveillance response systems

Ordinary differential equations

Data availability

The data and code will be made available at the time of publishing at https://github.com/SwissTPH/ZanzibarRCDmodel.

© 2022 The Author(s). Published by Elsevier B.V.

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