Vector-borne diseases (VBD) affect animals, plants and humans often resulting in an enormous burden on human health and economies. Mathematical models play an important role in our theoretical understanding of these diseases owing to their ability to summarize complex spatio-temporal dynamics with a limited number of parameters and variables. The classical theoretical models of VBDs make multiple simplifying assumptions such as spatial homogeneity and homogeneous biting to describe the interaction between vectors and hosts. While this theory was instrumental in the identification of the key driving factors of malaria transmission, our understanding of VBD in realistic spatial settings remains incomplete. To address this issue, recent theoretical frameworks are beginning to emphasize the importance of spatial complexities. Moreover, recent syntheses of the theory suggest that understanding the consequences of heterogeneities in (1) spatial transmission intensity, (2) individual risk of infection, and (3) host movement remain the most important gaps in our knowledge. Though these all occur in tandem in reality, few studies have explicitly addressed the interaction of these independent effects. Here we ask how individual heterogeneity in risk, host movement and spatial variation in transmission intensity influence malaria long-term persistence and prevalence. To address these questions we studied a multi-patch adaptation of the Ross-Macdonald modeling framework for malaria dynamics.
Results/Conclusions
Simulations from our multi-patch modeling framework showed that (1) spatial heterogeneity in transmission increased prevalence and persistence (R0). Spatial homogeneity in transmission intensity resulted in the lowest prevalence and persistence of all landscape configurations. (2) Disease prevalence decreased with increasing heterogeneity in individual risk of infection. In contrast, R0 increased with increasing individual heterogeneity. (3) Prevalence remains relatively unchanged with increasing rates of host movements from high to low transmission patches. In contrast, R0 increases with increasing rates of movements. All in all, our results show how prevalence and persistence—two important measures of VBD transmission—display a complex non-monotonic relationship as a result of spatial complexities.