Clinical morbidity of single or mixed schistosome species infection in two communities of southern Malawi

As part of a larger community-based epidemiological study entitled Hybridisation in Uro-Genital Schistosomiasis (HUGS), a parasite infection and clinical morbidity sub-study, implementing portable ultrasonography annually, was undertaken upon 701 participants from two communities in Mangochi and Nsanje Districts, southern Malawi. Our aim was to document the clinical morbidity a year after praziquantel treatment in those with previously proven human and/or zoonotic schistosomiasis, repeated a calendar year later after biannual praziquantel treatment. The median participant age was 12.0 years, with 293 (41.8%) having urinary Schistosoma haematobium egg-patent infections. Upon molecular analyses, these participants were co-infected with S. mansoni (29, 9.9%), S. mattheei (38, 13.0%), and six were infected with all three schistosome species occurring concurrently. A total of 166 participants (23.7%) had abnormal bladder wall thickness, 72 severely abnormal thickened bladder walls and 7 had bladder wall masses, among other abnormalities by ultrasonography. On the second annual follow-up, 203 participants were available (median age: 22.0 years), and of these, 27 (13.3%) presented with urinary S. haematobium egg-patent infections, with 2 (1.0%) having Schistosoma mansoni, 8 (3.9%) having Schistosoma mattheei and 2 with all species concurrently. Of these, only six participants (3.0%) had severely abnormal thickened bladder walls and other abnormalities. Overall, greater morbidity was observed in those with S. haematobium alone than in those with mixed species infections. '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'.