Impact of Asymptomatic Malaria on Some Hematological Parameters in the Iwo Community in Southwestern Nigeria

AbstractObjective: To determine the prevalence of asymptomatic malaria among prospective blood donors and its effect on some hematological parameters. Subjects and Methods: Six hundred sixty-eight seemingly healthy individuals (501 men and 167 women) ≧16 years of age and without clinical symptoms in Iwo, Southwestern Nigeria, were screened for this study. A sample of 5 ml of blood was drawn from each participant for examination of malaria parasites and a full blood count. Thick and thin Giemsa-stained blood smears were prepared for malaria parasite identification and quantification. Estimations of hematocrit, hemoglobin concentration, and platelet and leukocyte counts were made using an automated Coulter counter (STKS model). Results: Out of the 668 participants examined, 141 (21.1%) were positive for malarial parasitemia. The parasite rate was significantly higher in men (25.5%) than in women (7.8%) (χ 2 = 23.29, p < 0.001) and it was significantly associated with age (χ 2 = 33.69, p < 0.001). Parasitemic participants had significantly lower mean values of hematocrit, hemoglobin concentration, and total leukocyte and platelet counts compared to aparasitemic individuals (t = 3.5, p < 0.001; t = 2.0, p = 0.04; t = 4.4, p < 0.001, and t = 5.3, p < 0.001, respectively). A low platelet count (<150 × 10 9 /l) was significantly associated with malarial infection (OR 4.0; 95% CI 2.6–6.1). A person with a platelet count <150 × 10 9 /l was 4 times more likely to have asymptomatic malarial infection than one with a count ≧150 × 10 9 /l. Conclusion: Asymptomatic malaria is prevalent among blood donors in the study area and is associated with thrombocytopenia.