Malaria incidence and prevalence on Pemba Island before the onset of the successful control intervention on the Zanzibar Archipelago

• Published in: Malaria Journal
• Main Authors: Othman Mashavu K, Ramsan Mahdi, Deb Saikat, Dutta Arup, Sullivan David J, Jaenisch Thomas, Gaczkowski Roger, Tielsch James, Sazawal Sunil
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2010
• Subjects: Arctic medicine. Tropical medicine; RC955-962; Infectious and parasitic diseases; RC109-216; Arctic; Holo
• Online Access: https://doi.org/10.1186/1475-2875-9-32; https://doaj.org/article/e22bdafd58254e05b04ccc2a8717447c

Abstract Background Malaria incidence has been reported to decrease substantially in parts of sub-Saharan Africa, including the Zanzibar Archipelago in East Africa. A cohort study with an intensive follow-up on Pemba Island just before the onset of the highly successful malaria control intervention was conducted. The reported estimates of parasite prevalence and incidence can serve as a robust baseline to evaluate the effect size of the successful interventions and the potential contribution of quality controls and other factors associated with research studies in the decreased estimate of transmission. Methods In a rural clinic, two successive cohorts of 537 children total aged 2-23 months were followed for six months each with an intensive visitation schedule of bi-weekly follow-up. Robust estimates of incidence and prevalence according to four different malaria definitions were obtained. Results Malaria incidence and prevalence placed Pemba Island in a hyperendemic rather than holoendemic setting for the years 2003-2005. Overall parasite prevalence was estimated to be 39% - with monthly estimates varying between 30% and 50%. Incidence of malaria varied between 2.3 and 3.8 malaria episodes per year based on a diagnosis of fever and various microscopy-based parasite thresholds and between 4.8 and 5.7 based on a diagnosis of fever and 100 parasites/microliter analogous to detection by rapid diagnostic tests. Both parasite densities and malaria incidence increased with age and rainy season. Malaria incidence also varied substantially between the individual villages within the study area. Conclusions Pemba Island was previously considered holo-endemic for Malaria. The data suggest that the transmission situation on Pemba Island was significantly lower in 2003-2005 suggesting a hyper-endemic or meso-endemic transmission environment. The figures were obtained just before the onset of the highly successful malaria control intervention by impregnated bed nets and IRS on the Zanzibar Archipelago and provide robust ...