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Risk of imported malaria infections in Zanzibar: a cross-sectional study

Fakih, B. S. and Holzschuh, A. and Ross, A. and Stuck, L. and Abdul, R. and Al-Mafazy, A. H. and Irema, I. and Mbena, A. and Thawer, S. G. and Shija, S. J. and Aliy, S. M. and Ali, A. and Fink, G. and Yukich, J. and Hetzel, M. W.. (2023) Risk of imported malaria infections in Zanzibar: a cross-sectional study. Infect Dis Poverty, 12. p. 80.

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Abstract

BACKGROUND: Zanzibar has made substantial progress in malaria control with vector control, improved diagnosis, and artemisinin-based combination therapy. Parasite prevalence in the population has remained around 1% but imported infections from mainland Tanzania contribute to sustained local transmission. Understanding travel patterns between mainland Tanzania and Zanzibar, and the risk of malaria infection, may help to control malaria importation to Zanzibar. METHODS: A rolling cross-sectional survey linked to routine reactive case detection of malaria was carried out in Zanzibar between May 2017 and October 2018. Households of patients diagnosed with malaria at health facilities were surveyed and household members were tested for malaria using rapid diagnostic tests and a sub-sample by quantitative PCR (qPCR). Interviews elicited a detailed travel history of all household members who had travelled within the past two months, including trips within and outside of Zanzibar. We estimated the association of malaria infection with travel destinations in pre-defined malaria endemicity categories, trip duration, and other co-variates using logistic regression. RESULTS: Of 17,891 survey participants, 1177 (7%) reported a recent trip, of which 769 (65%) visited mainland Tanzania. Among travellers to mainland Tanzania with travel destination details and a qPCR result available, 241/378 (64%) reported traveling to districts with a 'high' malaria endemicity and for 12% the highest endemicity category was 'moderate'. Travelers to the mainland were more likely to be infected with malaria parasites (29%, 108/378) than those traveling within Zanzibar (8%, 16/206) or to other countries (6%, 2/17). Among travellers to mainland Tanzania, those visiting highly endemic districts had a higher odds of being qPCR-positive than those who travelled only to districts where malaria-endemicity was classified as low or very low (adjusted odd ratio = 7.0, 95% confidence interval: 1.9-25.5). Among travellers to the mainland, 110/378 (29%) never or only sometimes used a mosquito net during their travel. CONCLUSIONS: Strategies to reduce malaria importation to Zanzibar may benefit from identifying population groups traveling to highly endemic areas in mainland Tanzania. Targeted interventions to prevent and clear infections in these groups may be more feasible than attempting to screen and treat all travellers upon arrival in Zanzibar.
Faculties and Departments:09 Associated Institutions > Swiss Tropical and Public Health Institute (Swiss TPH)
09 Associated Institutions > Swiss Tropical and Public Health Institute (Swiss TPH) > Department of Epidemiology and Public Health (EPH) > Biostatistics > Biostatistics Frequentist Modelling (Kwiatkowski)
09 Associated Institutions > Swiss Tropical and Public Health Institute (Swiss TPH) > Department of Epidemiology and Public Health (EPH) > Health Interventions
09 Associated Institutions > Swiss Tropical and Public Health Institute (Swiss TPH) > Department of Epidemiology and Public Health (EPH) > Health Interventions > Intervention Effectiveness and Impact (Hetzel)
09 Associated Institutions > Swiss Tropical and Public Health Institute (Swiss TPH) > Department of Epidemiology and Public Health (EPH) > Household Economics and Health Systems Research > Epidemiology and Household Economics (Fink)
06 Faculty of Business and Economics > Departement Wirtschaftswissenschaften > Professuren Wirtschaftswissenschaften > Epidemiology and Household Economics (Fink)
03 Faculty of Medicine > Departement Public Health > Sozial- und Präventivmedizin > Medicines Development (Paris)
09 Associated Institutions > Swiss Tropical and Public Health Institute (Swiss TPH) > Department of Medicine (MED) > Medicines Development (Paris)
UniBasel Contributors:Fakih, Bakar and Holzschuh, Aurel and Ross, Amanda and Thawer, Sumaiyya and Fink, G√ľnther
Item Type:Article, refereed
Article Subtype:Research Article
ISSN:2049-9957 (Electronic)2095-5162 (Print)2049-9957
Note:Publication type according to Uni Basel Research Database: Journal article
Language:English
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Last Modified:24 Oct 2023 07:14
Deposited On:24 Oct 2023 07:14

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