Over-dispersion in malaria-schistosoma co-infection: insights from a meta-analytical approach and systematic review

Malaria and schistosomiasis are two major parasitic diseases that are co-endemic in many regions of sub-Saharan Africa. Despite their frequent geographical overlap, the potential epidemiological patterns and potential interactions associated with Plasmodium--Schistosoma co-infection remain poorly characterized. This study aimed to systematically assess the epidemiology of malaria-schistosomiasis co-infection and to quantify whether co-infections occur more frequently than expected under an assumption of independence between the two infections.

We conducted a systematic review and meta-analysis in accordance with the PRISMA 2020 guidelines. A total of 192 studies published between 1996 and 2023 were included in the qualitative synthesis, of which 59 studies involving 73,383 individuals were included in the meta-analysis. Pooled odds ratio (ORs) were estimated to compare observed and expected co-infection prevalence.

The pooled analysis showed that Plasmodium-Schistosoma co-infection occurs more frequently than expected by chance (overall OR = 1.20, 95% CI 1.02-1.40), despite substantial heterogeneity across studies (I² = 89%). Reported co-infection prevalence ranged from 1.1% in Benin to 36.6% in Mali. School-age children and pregnant women were disproportionately affected. Subgroup analyses revealed no consistent differences according to sex or parasite species.

These findings indicate a non-random distribution of malaria-schistosomiasis co-infection in sub-Saharan Africa, consistent with epidemiological over-dispersion. Although the underlying biological and immunological mechanisms remain uncertain, the widespread co-occurrence of these parasites highlights the importance of integrated surveillance and control strategies that account for polyparasitism in endemic settings.