A Weighted Surveillance Approach for Detecting Chronic Wasting Disease Foci

A key component of wildlife disease surveillance is detennining the spread and geographic extent ofpatbogems by nionitoring for infected individnals in regions where cases have not been previonsly ch.,,tected. A pracitical Challenge if such Surveillance is developing refiable, yet cost-effe ctive, approaches that reinain sustainable when nionitoring needs are prolonged or continuous, or wheni resources to stipport-these efforts are finited. In order to finprove the efficiency of chronic wasting disease (CWD) Surveillance in Colorado, United States, we developed a weighted surveillance systent exploiting observed differences in CWD prevalence across deniographic strata within infected naile deer (Odocoileus heinionus) populations. NVe nsed field data to est-finate sarnpling weights for individuals froin eight deniographic strata distinguished bv differences in apparent health. sex, zinc age. In this systeni, individuals froin a sample source with high prevalence and low inclusion probability (e.g., clinical OVE) stispects) received >= 10.3 tinies inore Nveight than those froin a source with low prevalence and high inclusion probability (e.g., apparently healthy, hunter-barvested individuals). We sinnilated use of this alternatiive surveillance SvS ern foi- a deer wanagenient unit in Colorado and evaluated the potential effects of using biased weights on lie probability offailing to detect OVID and on relative SUrveillance costs. We formed that his svstent shotild he transpareiit, cost-effective, and reasonably robost to the inadvertent use of biased weights. By inipleinenting this, or a shnilar, weighted stirveillance system, wildlife agencies should be able to inaintain or- iniprove current surve illance standards while, perhaps, collecting and exannning fewer- sainples, thereby increasing the efficiency and cost effectiveness of ongoing CWD surveillance programs.