Tracking the spatial and longitudinal dynamics of mixed infections of urogenital and intestinal schistosomiasis, inclusive of Schistosoma mattheei, in two sentinel rural communities from southern Malawi

The World Health Organization's 2030 neglected tropical disease roadmap aims to eliminate schistosomiasis as a public health problem with preventive chemotherapy (PC) as a foundational stratergy; however, mixed infections of Schistosoma haematobium with zoonotic species, inclusive of putative hybrids, present a potential challenge. We sought to address the importance of mixed species infections through a 2-year, longitudinal epidemiological investigation at two villages in southern Malawi (Samama and Mthawira). Participants (approx. 2000) were sampled at baseline (BL), a 12-month follow-up (FU1) and a 24-month follow-up (FU2). PC was provided annually (BL-FU1) and biannually (FU1-FU2). Urine samples underwent microscopical examination and circulating cathodic antigen (CCA) rapid-diagnostic testing, with egg-patent urine filters undergoing additional molecular screening for five non-S. haematobium species using real-time polymerase chain reaction (rtPCR). Prevalence of schistosomiasis by microscopy was statistically higher in Samama than Mthawira (±0.0563, p-value = 1.3 × 10 -11), as was mixed infections with Schistosoma mattheei, by rtPCR (± 0.17, p-value = 3.84 × 10 -10). By FU2, PC reduced the prevalence of S. haematobium and Schistosoma mansoni, but that of S. mattheei remained relatively stable, rising by 0.98% at Samama (± 0.19, p-value = 0.41) and decreasing by 0.43% at Mthawira (± 0.39, p-value = 0.33). We conclude that treatment alone will not be sufficient for control of zoonotic S. mattheei, but additional interventions will be required. This article is part of the Royal Society Science+ meeting issue 'Parasite evolution and impact in action: exploring the importance and control of hybrid schistosomes in Africa and beyond'.