Use of spatial clusters by red deer (Cervus elaphus) to identify transmission hot spots in a Chronic Wasting Disease context

• Main Author: Skjelbostad, Isa Nergård
• Format: Master Thesis
• Language: English
• Published: 2020
• Subjects: CWD; cluster; spatial clusters; cervus elaphus; chronic wasting disease; prion; aggregation; red deer; disease transmission; Nordfjella; Norway; Rangifer tarandus
• Online Access: http://hdl.handle.net/10852/79616; http://urn.nb.no/URN:NBN:no-82802

Abstract In 2016 Chronic Wasting Disease was discovered in Nordfjella, Norway for the first time in a female reindeer (Rangifer tarandus). Since then Norwegian nature management have implemented several measures in the affected area in Nordfjella and its surrounding municipalities to stop the spread of the prion disease. The prions’ long viability in soil outside of a host body increases the risk of spillover to other cervid species. The risk is especially high for the red deer (Cervus elaphus) population of Lærdal being the densest population in the Nordfjella region, and with its overlapping summer ranges with the affected reindeer herd. Norwegian red deer have been studied for a long time and a lot is known about their broad scale habitat selection and seasonal migration patterns. However, little is known about when and why the red deer repeatedly use the same locations on a fine scale, which has become a more relevant topic now as it may facilitate disease transmission. With location data from 14 red deer in Lærdal from 2017 to 2019, and through field work in Lærdal, I have quantified the proportion of spatial clusters containing natural forage, supplemental forage aimed for cervids and supplemental forage not aimed for cervids. I have also been able to quantify the seasonal pattern of number of spatial clusters. I found that non-intentional feeding caused as much as 31% of the clustering in infield habitats, and that most of this was in the form of leftover silage dumped in fields. I found that non-intentional feeding facilitates the contact between cervid species, and that it therefore can facilitate the spillover of Chronic Wasting Disease from reindeer, through red deer, and to roe deer (Capreolus capreolus) or other cervid species that do not have overlapping ranges with reindeer. Aggregation in infield habitat and around non-intentional feeding was more frequent during periods with more snow. Lastly, I discovered during the field work that even though there is a requirement of fencing in hay bales to help minimize aggregation of cervids in Lærdal, there were several cases of lack of compliance to this. To reduce the amount of contact within red deer and between cervid species additional measures to limit the amount of silage dumped in fields may need to be installed. In addition, it may be necessary to enforce the requirement of fencing around hay bales to ensure compliance.