Land use impacts on parasitic infection: a cross-sectional epidemiological study on the role of irrigated agriculture in schistosome infection in a dammed landscape.

Background: Water resources development promotes agricultural expansion and food security. But are these benefits offset by increased infectious disease risk? Dam construction on the Senegal River in 1986 was followed by agricultural expansion and increased transmission of human schistosomes. Yet the mechanisms linking these two processes at the individual and household levels remain unclear. We investigated the association between household land use and schistosome infection in children.

Methods: We analyzed cross-sectional household survey data (n = 655) collected in 16 rural villages in August 2016  across demographic, socio-economic and land use dimensions, which were matched to Schistosoma haematobium (n = 1232) and S. mansoni (n = 1222) infection data collected from school-aged children. Mixed effects regression determined the relationship between irrigated area and schistosome infection presence and intensity.

Results: Controlling for socio-economic and demographic risk factors, irrigated area cultivated by a household was associated with an increase in the presence of S. haematobium infection (odds ratio [OR] = 1.14; 95% confidence interval [95% CI]: 1.03-1.28) but not S. mansoni infection (OR = 1.02; 95% CI: 0.93-1.11). Associations between infection intensity and irrigated area were positive but imprecise (S. haematobium: rate ratio [RR] = 1.05; 95% CI: 0.98-1.13, S. mansoni: RR = 1.09; 95% CI: 0.89-1.32).

Conclusions: Household engagement in irrigated agriculture increases individual risk of S. haematobium but not S. mansoni infection. Increased contact with irrigated landscapes likely drives exposure, with greater impacts on households relying on agricultural livelihoods.