Abstract

Chronic wasting disease (CWD) has been endemic in northern Colorado for over 2 decades. We analyzed prevalence data from mule deer (Odocoileus hemionus) populations in Larimer County to discern the likely influences of temporal, spatial, and demographic factors on patterns observed in naturally infected populations and to look for evidence that recent management actions have affected temporal trends. We observed spatial heterogeneity among wintering mule deer subpopulations, marked difference in CWD prevalence by sex and age groups, and clear local trends of increasing prevalence over a 7-yr period that largely preceded management intervention. For both sexes, prevalence peaked in the 4–6-yr old age class, with the largest increase occurring between the 2–3-yr-old and 4–6-yr-old age classes. This differential was larger for males (5.9% among 2–3-yr-olds vs. 19.4% among 4–6-yr-olds; p=0.0002). Demographic, spatial, and temporal factors all appear to contribute to the marked heterogeneity in CWD prevalence in endemic portions of North Central Colorado. These factors likely combine in various ways to influence epidemic dynamics and responses to management on both local and broad geographic scales.