Background: Blood transfusion saves life of patients with severe anaemia. However, blood transfusion can transmit blood-borne parasites. Despite malaria being endemic in Tanzania, there is limited information on asymptomatic malaria among blood donors. This study determined the prevalence and associated factors of asymptomatic malaria among blood donors at the Lake Zone Victoria Blood Transfusion Centre in Mwanza, Tanzania.

Methods: A cross-sectional study was conducted between March and April 2016 among blood donors without any symptoms of malaria. During blood donation, samples were collected from each participant. Malaria parasites were detected microscopically from Giemsa stained thin and thick smears and by the use of malaria rapid diagnostic test (MRDT).

Results: A total of 150 blood donors participated in this study. The median age of participants was 20 (IQR: 18-27) years. Malaria prevalence by microscopy was 5.3% (95% CI: 1.7-8.8) while by MRDT was 8% (95% CI: 3.6-12.3). Malaria mean parasite density was 12mps/200WBC. Only individuals who reported using mosquito nets were found to be protected from getting asymptomatic malaria on multivariate logistic regression analysis (OR: 0.04, 95% CI: 0.01-0.25, P<0.001).

Conclusion: A considerable proportion of blood donors in Mwanza, Tanzania are infected with P. falciparum which poses a risk for transmission to blood recipients including malaria vulnerable groups like pregnancy woman and children. Screening donated blood for malaria parasites is recommended in malaria endemic areas to prevent possible fatal consequences.