Cooperative Fish and Wildlife Research Units Program: Montana Cooperative Wildlife Research Unit
Education, Research and Technical Assistance for Managing Our Natural Resources

Spatiotemporal causal inference methods are needed to detect the eect of interventionson indirectly measured epidemiological outcomes that go beyond studying spatiotemporalcorrelations. Chronic wasting disease (CWD) causes neurological degeneration and even-tual death to white-tailed deer (Odocoileus virginianus) in Wisconsin. Targeted cullinginvolves removing deer after traditional hunting seasons in areas with high CWD preva-lence. The evaluation of the causal eects of targeted culling in the spread and growthof CWD is an important unresolved research and CWD management question that canguide surveillance eorts. Reaction-diusion partial dierential equations (PDEs) can beused to mechanistically model the underlying spatiotemporal dynamics of wildlife diseases,like CWD, allowing researchers to make inference about unobserved epidemiological quan-tities. These models indirectly regress spatiotemporal covariates on diusion and growthrates parameterizing such PDEs, obtaining associational conclusions. In this work we de-velop an innovative method to obtain causal estimators for the eect of targeted culling interventions on CWD epidemiological processes using an inverse-probability-of-treatment-weighted technique by means of marginal structural models embedded in the PDE ttingprocess. Additionally we establish a novel scheme for sensitivity analysis under unmea-sured confounder for testing the hypothesis of a signicant causal eect in the indirectlymeasured epidemiological outcomes. Our methods can be broadly used to study the impactof spatiotemporal interventions and treatment exposures in the epidemiological evolutionof infectious diseases that can help to inform future eorts to mitigate public health im-plications and wildlife disease burden.