Haematological responses in children under 5 years with malaria and soil-transmitted helminth coinfections in Delta State, Nigeria: a cross-sectional study

Background: Malaria and soil-transmitted helminth (STH) infections often co-occur in Nigerian children under 5 years of age, affecting haematological functions. However, local data on their combined effect are limited. Objectives: To determine the prevalence and impact of malaria, STH and malaria–STH co-infection on haematological parameters in children under five in the Delta South Senatorial District in Nigeria. Design: Hospital-based cross-sectional study. Methods: A total of 269 children under 5 years of age attending selected health centres were recruited across the Delta South Senatorial District. Malaria was diagnosed by microscopy, STH by stool analysis and haematological parameters were measured using automated techniques. Associations between infection status, demographics, clinical characteristics and haematological indices were examined with descriptive statistics, T -test, ANOVA and correlation analyses. Results: Co-infection was most common in toddlers aged 1–2 years (40.9%) and was more frequent in males. Normal haemoglobin genotype (Hb AA) predominated (57.3%), followed by sickle cell trait (Hb AS) (36.3%) and sickle cell disease (Hb SS) (6.3%). Children with Hb SS had lower haemoglobin, packed cell volume (PCV) and red blood cell (RBC) counts, but higher white blood cell levels ( p < 0.01). Children with malaria or STH, especially those with co-infection, showed a macrocytic hypochromic pattern with increased mean corpuscular volume and reduced mean corpuscular haemoglobin concentration ( p < 0.001), despite only mild, non-significant reductions in haemoglobin and RBC counts. Parasitaemia varied with age ( p = 0.033) but showed weak correlations with haemoglobin, RBC and PCV, suggesting that anaemia was influenced more by host factors than by parasite burden. Hb AS children had higher parasite loads but better red cell indices; Hb SS cases showed the greatest haematological derangement, particularly when coinfected. Conclusion: Malaria and STH infections remain a major cause of haematological abnormalities in children under five. Early red cell alterations, especially macrocytosis and hypochromia, preceded obvious anaemia and were more strongly influenced by host factors than by parasite density, underscoring the need for integrated control and careful haematological assessment in endemic settings.