Fine-scale spatial mapping of anaemia within two sentinel study communities associated with urogenital schistosomiasis in Malawi

While a causal link between urogenital schistosomiasis  ( Schistosoma haematobium ) and anaemia is well  established, quantitative associations between infection  intensity and haemoglobin levels across endemic communities,  at fine spatial scales, remain insufficiently characterized.  As part of the broader Hybridisation in Urogenital  Schistosomiasis (HUGS) investigation, we studied the  micro-epidemiology of anaemia within two study communities  in southern Malawi where S. haematobium remains endemic. Urine samples were examined by microscopy to quantify  S. haematobium infection intensity, categorised as  low (0–9 eggs/10 mL), moderate (10–49 eggs/10 mL), and  heavy (≥50 eggs/10 mL). Individual haemoglobin concentrations  were measured using a HemoCue photometer in 1,149 participants  from Samama village (Mangochi District) and 977 participants  from Mthawira village (Nsanje District). Linear geostatistical  models incorporating individual-level characteristics and  spatial covariates were used to estimate anaemia prevalence  at fine geographical scales. Moderate anaemia (Hb 80–109 g/L) was most prevalent among  children aged 6–12 years (45.30% in Samama and 39.54% in  Mthawira), while severe anaemia was more frequent among  adults aged ≥19 years in both villages. Increasing  S. haematobium infection intensity was associated  with lower haemoglobin levels, with individuals harbouring  heavy infections being at greater risk of moderate-to-severe  anaemia. Spatial modelling revealed longer-range spatial  correlation in Nsanje (ϕ = 66.7 km) than in Mangochi  (ϕ = 25.5 km), indicating more spatially persistent risk  in Nsanje and more localised heterogeneity in Mangochi.  Predicted anaemia prevalence among female children aged  6–12 years with moderate infection intensity ranged from  25–65% in Mangochi and 64–76% in Nsanje. At the micro-epidemiological level, S. haematobium   infection intensity was associated with the severity of  anaemia, with substantial spatial heterogeneity within and  between villages. Identification of high-risk clusters  supports targeted interventions, including stepped-up  preventive chemotherapy, improved water and sanitation,  and iron supplementation.