Risk factors associated with malaria infection identified through reactive case detection in Zanzibar, 2012–2019

• Published in: Malaria Journal
• Main Authors: Humphrey R. Mkali, Erik J. Reaves, Shabbir M. Lalji, Abdul-Wahid Al-mafazy, Joseph J. Joseph, Abdullah S. Ali, Faiza B. Abbas, Mohamed H. Ali, Wahida S. Hassan, Chonge Kitojo, Naomi Serbantez, Bilali I. Kabula, Ssanyu S. Nyinondi, Donal Bisanzio, Mike McKay, Erin Eckert, Richard Reithinger, Jeremiah M. Ngondi
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2021
• Subjects: Malaria; Travel; Vector control; Elimination; Zanzibar; Arctic medicine. Tropical medicine; RC955-962; Infectious and parasitic diseases; RC109-216; Arctic
• Online Access: https://doi.org/10.1186/s12936-021-04025-1; https://doaj.org/article/b8dc5e29d58d47f39cfb5dd74bc4ec1d

Abstract Background Over the past two decades, Zanzibar substantially reduced malaria burden. As malaria decreases, sustainable improvements in control interventions may increasingly depend on accurate knowledge of malaria risk factors to further target interventions. This study aimed to investigate the risk factors associated with malaria infection in Zanzibar. Methods Surveillance data from Zanzibar’s Malaria Case Notification system from August 2012 and December 2019 were analyzed. This system collects data on malaria cases passively detected and reported by all health facilities (index cases), and household-based reactive case detection (RCD) activities linked to those primary cases. All members of households of the index cases were screened for malaria using a malaria rapid diagnostic test (RDT). Individuals with a positive RDT were treated with artemisinin-based combination therapy. Univariate and multivariate logistic regression analyses were done to investigate the association between RDT positivity among the household members and explanatory factors with adjustment for seasonality and clustering at Shehia level. Results A total of 30,647 cases were reported of whom household RCD was completed for 21,443 (63%) index case households and 85,318 household members tested for malaria. The findings show that younger age (p-value for trend [Ptrend] < 0.001), history of fever in the last 2 weeks (odds ratio [OR] = 35.7; 95% CI 32.3–39.5), travel outside Zanzibar in the last 30 days (OR = 2.5; 95% CI 2.3–2.8) and living in Unguja (OR = 1.2; 95% CI 1.0–1.5) were independently associated with increased odds of RDT positivity. In contrast, male gender (OR=0.8; 95% CI 0.7–0.9), sleeping under an LLIN the previous night (OR = 0.9; 95% CI 0.7–0.9), having higher household net access (Ptrend < 0.001), and living in a household that received IRS in the last 12 months (OR = 0.8; 95% CI 0.7–0.9) were independently associated with reduced odds of RDT positivity. A significant effect modification of combining IRS and ...