  Infectious disease can reduce labor productivity and incomes, trapping
subpopulations in a vicious cycle of ill health and poverty. Efforts to boost
African farmers' agricultural production through fertilizer use can
inadvertently promote the growth of aquatic vegetation that hosts disease
vectors. Recent trials established that removing aquatic vegetation habitat for
snail intermediate hosts reduces schistosomiasis infection rates in children,
while converting the harvested vegetation into compost boosts agricultural
productivity and incomes. Our model illustrates how this ecological
intervention changes the feedback between the human and natural systems,
potentially freeing rural households from poverty-disease traps. We develop a
bioeconomic model that interacts an analytical microeconomic model of
agricultural households' behavior, health status and incomes over time with a
dynamic model of schistosomiasis disease ecology. We calibrate the model with
field data from northern Senegal. We show analytically and via simulation that
local conversion of invasive aquatic vegetation to compost changes the
feedbacks among interlinked disease, aquatic and agricultural systems, reducing
schistosomiasis infection and increasing incomes relative to the current status
quo, in which villagers rarely remove vegetation. Aquatic vegetation removal
disrupts the poverty-disease trap by reducing habitat for snails that vector
the infectious helminth and by promoting production of compost that returns to
agricultural soils nutrients that currently leach into surface water from
on-farm fertilizer applications. The result is healthier people, more
productive labor, cleaner water, more productive agriculture, and higher
incomes.
