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  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 S.
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). Conclusion: 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.