Polyparasitism in north-western Madagascar: prevalence, co-infection patterns and differences between conventional and molecular diagnostics

In co-endemic tropical settings, control strategies remain largely vertical despite concurrent exposure to multiple pathogens. In north-western Madagascar, intestinal parasitic infections (IPIs), urogenital schistosomiasis, and malaria overlap geographically, yet integrated epidemiological data combining microscopy and molecular diagnostics remain limited. The primary objective was to explore the observed prevalence and co-infection patterns of stool parasites, Schistosoma haematobium , and Plasmodium spp. among voluntarily recruited residents of three rural localities in north-western Madagascar; a secondary objective was to compare detection by conventional and molecular diagnostic methods. We conducted a cross-sectional community-based study (August 2025) in three rural localities in north-western Madagascar. Residents of all ages were eligible, and participants were enrolled on a voluntary basis without probability-based sampling. Stool samples were examined microscopically for intestinal parasites, while S. haematobium was assessed by urine microscopy and real-time PCR, and Plasmodium spp. by rapid diagnostic testing and real-time PCR of dried blood spots. Statistical analyses were performed in R to describe observed prevalence and co-infection patterns and to explore associations with demographic, environmental, and selected haematological variables. Among 340 participants (median age 8 years; 55% female), 198/340 (58.2%) harbored at least one stool parasite and 223/340 (65.6%) were infected with S. haematobium , whereas Plasmodium infection was detected in 23/340 participants (6.8%). However, pathogenic stool parasites( Giardia intestinalis , Hymenolepis nana , hookworm, Trichuris trichiura ) were identified in 86/340 (25.3%) of individuals. Real-time PCR identified 146 additional S. haematobium infections compared with urine microscopy and 22 additional Plasmodium infections compared with RDT. Co-infections were common (62.4% with S. haematobium plus ≥ 1 intestinal parasite), with age-dependent patterns. Haematological differences between infected and uninfected participants were generally modest, although some parameters differed significantly for pathogenic stool parasite and S. haematobium infections.Polyparasitism is highly prevalent, yet distinguishing between environmental exposure and clinically actionable infection substantially refines estimates of treatment need. Integrating molecular diagnostics into surveillance frameworks may improve resource allocation and supports a shift toward multi-pathogen, community-based screening strategies in co-endemic regions.