Investigating the impact of Schistosoma haematobium infection on immunity to Plasmodium falciparum malaria in populations from Burkina Faso.

INTRODUCTION. Several studies indicate that infection with helminths might modulate the immune response towards intracellular pathogens including Plasmodium. We recently reported that in rural villages of Burkina Faso the seroprevalence of Strongyloides stercoralis, Wuchereria bancrofti and Schistosoma haematobium was 5%, 16% and 63% respectively, in line with estimates of infection prevalence in the region for the three parasites. The aim of the present investigation was to assess the impact of serological markers of S. hematobium infection on the prospective risk of Plasmodium falciparum parasitaemia among study populations, using a repeated cross-sectional surveys design. MATERIALS AND METHODS. IgM and IgG against S. haematobium Soluble Worm Antigen Protein (SWAP) and Soluble Egg Antigen (SEA) were measured by an in-house ELISA protocol in plasma samples collected from N=452 subjects. Statistical analysis was performed using STATAv13. Association analysis between the presence of S. haematobium-specific antibodies at baseline and the number of P. falciparum infections over 5 surveys was conducted using Poisson regression adjusting for age, sex, ethnicity and haemoglobin genotype. RESULTS AND CONCLUSIONS. Association analysis showed a significant increase in the incidence of P. falciparum infections among anti-S.haematobium seropositive subjects (IRR=1.30, 95%CI= 1.09-1.57, p-value= 0.004). These observations are in line with those of a systematic review and meta-analysis indicating an association between S. haematobium infection and increased prevalence of P. falciparum asymptomatic/uncomplicated malaria.