Determinants of schistosoma mansoni transmission in hotspots at the late stage of elimination in Egypt

Abstract Purpose To investigate the role of human practices and environmental factors in maintaining the transmission chain. Study Design a Cross-section study was conducted between July and November 2019 to determine the effect of malacological and environmental factors on the prevalence of Schistosoma mansoni (S.mansoni) in Kafr El-Sheikh (KES). Methods 2259 fecal samples were collected from 861recruitted children aged 6-15 years. Simultaneously, water and snail samples were collected from watercourses surrounding their houses. Results Prevalence of Schistosoma mansoni infection was significantly higher during summer than during fall (19.1% Vs 7.2%, respectively, p <0.01).The intensity of infection (light, moderate, and heavy) during summer versus fall was (93.55% vs 89.38%, 6.45% vs 8.85, and 0.00% vs 1.77%), P<0.05. Higher prevalence of human infection was identified among males than females (OR=1.63, CI: 1.10-2-40), children aged 11-15 years than among counterparts aged 6-10 years, (OR=2.96), and if mothers were of low educational level (OR=2.83, CI: 1.72-5.06). The main identified risk factors were contacting the main body of water-canal for either washing clothes, land irrigation, collecting waters, bathing, or garbage disposal (P<0.05). The count of collected Biomphalaria alexandrina (B. alexandrina) was statistically different across different seasons (p<0.01) in line with a similar significant difference in water temperature, salinity, turbidity, total coliforms (TC) concentration, depth, velocity, and water level (p<0.01). The presence of grasses and duckweeds had a significant association with snail infection (p = 0.00l). Water depth, pH, temperature, and total dissolved solids (TDS) significantly affected the snail count. Conclusions The persistence of the transmission cycle is mainly affected by the socioeconomic status, and the adopted risky behaviors of the local citizen. Over and above, environmental factors enhance snail survival and catching the cercarial infection.