Maternal chronic wasting disease infection restricts fetal head size in white-tailed deer ( <i>Odocoileus virginianus</i> )

Chronic wasting disease (CWD) is a fatal neurodegenerative prion disease of cervids that can be transmitted through direct physical contact, indirect contact with a contaminated environment, or vertical transmission. CWD is characterized by a long incubation period followed by symptoms like loss of appetite resulting from the destruction of brain tissue. While the consequences for infected animals are clear, a previous study from our laboratory showing lower body weights in the foetuses of CWD-positive female deer suggests those consequences may be intergenerational. In this study, we addressed the impact of maternal CWD infection on foetal head development (as a proxy for brain growth) in wild white-tailed deer using data from CWD management efforts in northern Illinois, U.S.A. Multivariate, multilevel, Bayesian Gamma regression found that maternal CWD infection reduced foetal head nose-occipital length and crown-jaw circumference by 6.76% and frontal-occipital length by 11.31%. These findings suggest impeded brain development in the offspring of CWD-infected female deer, which could reduce fawns' survival and success after birth and lead to a decline in population fitness over time. This study is the first to demonstrate the detrimental effects of a prion disease on foetal brain development in any animal species regardless of whether vertical transmission has occurred.