Fig. 1a, b

Model structure diagrams. a Diagrams of the model framework illustrating the complete transmission cycle, the human infection status with variable Schistosoma mansoni worm burden, and the age-stratified snail population. S Susceptible class, E exposed class, I infected class, I_C infected and castrated snails; I_L infected humans with a low S. mansoni burden, I_M infected humans with a moderate S. mansoni burden, I_H infected humans with a heavy S. mansoni burden. b The completely stratified model for the snail population includes neonatal (N), juvenile (J), small (S) and large (L) adult age classes; this is simplified in various combinations in later model structures. The colors represent the way in which the age classes are combined in each model structure. The missing age groups in all models, excluding the completely stratified model, are subsumed into the larger age class. For example, in the neonatal and juvenile and large (N+J+L) model, small adults are subsumed into the large adult age class. In the small and large (S+L) model, neonatal and juvenile snails are subsumed into the small adult snail class. In every version of the model the snails can still be assigned to any of the infection statuses