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'.