Malaria Elimination in Unguja Island Zanzibar: Individual Risk Factors for Continued Transmission.

Abstract Introduction: To achieve malaria elimination, understanding of the individual risk factors for malaria infection is critical to inform strategic planning and implementation. To address this, a community-based individual risk-factor study was conducted in Unguja Island Zanzibar.Methods: A matched case control study with a sample size of 103 cases and 309 controls was conducted in Unguja Island. Malaria cases from health facilities were reported via Unstructured Supplementary Service Data (USSD) mobile phones to a central database, after which an SMS alert was sent to the District Malaria Surveillance Officer’s (DMSO) mobile phone. DMSO followed up index cases up to household level and performed malaria test on all household members using rapid diagnostic tests (mRDT). Family members tested negative were considered as controls. Both cases and controls were interviewed with the same questionnaire. Data were analyzed using Epi-info version 3.5.1 using conditional logistic regression model. Results: The findings revealed that chance of malaria infection was higher among individuals who travelled outside Zanzibar [AOR = 60.47, 95% CI 15.73 - 232.44], who spend their time in outdoor activities during the night [AOR = 8.53, 95% CI 1.96 - 37.11], whose rooms were not sprayed with indoor residual spray (IRS) [AOR= 29.60, 95% CI 2.68 - 326.49] and those who did not have a bed net [AOR=16.25, 95% CI 3.32 - 79.50].Conclusion: Travel outside Zanzibar, outdoors activities during the night, lack of access to malaria interventions (IRS or bed nets) were the risk factors for malaria infection in Unguja. Ministry of Health should set a mechanism of encouraging people who travel to malaria endemic areas to attend the nearby health facility for malaria screening. Sensitizing people on using protective gear during the night and ensuring good coverage of malaria interventions would reduce the risk of malaria in Unguja Zanzibar.