A comparative cohort study of the effect of rainfall and temperature on diarrhoeal disease in faecal sludge and non-faecal sludge applying communities, Northern Ghana

This study assesses the effect of temperature and rainfall on diarrhoea incidence in sludge and non-faecal sludge applying farming communities in Northern Ghana. Diarrhoea episode data were obtained through an open cohort survey involving 1,341 and 1,323 individuals from the sludge and non-faecal sludge communities, respectively. The effects of temperature and rainfall variables on diarrhoea incidence were assessed using autoregressive Poisson regression models. Maximum rainfall events in the same bi-week increased the risk of diarrhoea in the sludge (relative risk, RR: 1.034; confidence interval, CI: 1.02–1.05) and non-sludge (RR: 1.003; CI: 0.99–1.01) communities. However, this was not significant in the non-sludge communities (p > 0.05). Minimum rainfall occurring in the same bi-week decreased the risk of diarrhoea in both communities. Maximum temperature decreased the risk of diarrhoea in the sludge communities (RR: 0.50; CI: 0.38–0.65), but increased the risk in the non-sludge communities (RR: 1.19 CI: 1.02–1.40). Minimum temperature increased diarrhoea disease risk (RR: 3.50; CI: 2.10–5.80) in the sludge communities, but decreased the risk (RR: 0.70; CI: 0.54–0.84) in the non-sludge communities. The study stresses the need to account for weather variables when developing schemes for the land application of faecal sludge.