Response attached.
Nice example Michelle.
Regarding your question: "reverse causality between SES and malaria cannot be ignored. However, I wonder if they measured SES at baseline, and investigated incidence of malaria—is this a strong possibility? I mean I could understand that malaria may cause persistence of poverty but would that be a different variable? "
In theory baseline SES and persistence of poverty are different variables, however, if malaria across the lifecourse is correlated, for example if the factors that increased risk of past malaria also increase risk of future incidence then past malaria history may influence baseline SES and this could be informally considered reverse causation, even though it is past malaria not onset of malaria (which is technically the outcome of the study).