Chronic wasting disease (CWD) has been recognized as an important prion disease in native North American deer and Rocky Mountain elk. The disease is a unique member of the transmissible spongiform encephalopathies (TSEs), which naturally affects only a few species. CWD had been limited to USA and Canada until 2000.
On 28 Dec 2000, information from the Canadian government showed that a total of 95 elk had been exported from farms with CWD to Korea. These consisted of 23 elk in 1994 originating from the so-called “source farm” in Canada and 72 elk in 1997 which had been held in pre-export quarantine at the source farm.
Based on export information of CWD-suspected elk from Canada to Korea, a CWD surveillance program was initiated by the Ministry of Agriculture and Forestry (MAF) in 2001. All elk imported in 1997 were traced back; however, elk imported in 1994 were impossible to identify.
CWD control measures included stamping out of all animals in the affected farm and thorough cleaning and disinfection of the premises. In addition, nationwide clinical surveillance of Korean native cervids and improved measures to ensure reporting of CWD suspect cases were implemented.
A total of 9 elk were found to be affected. CWD was designated as a notifiable disease under the Act for Prevention of Livestock Epidemics in 2002. Additional CWD cases — 12 elk and 2 elk — were diagnosed in 2004 and 2005. Since February 2005, when slaughtered elk were found to be positive, all slaughtered cervids for human consumption at abattoirs were designated as targets of the CWD surveillance program.
Currently, CWD laboratory testing is only conducted by the National Reference Laboratory on CWD, which is the Foreign Animal Disease Division (FADD) of the National Veterinary Research and Quarantine Service (NVRQS).
In July 2010, one out of 3 elk from Farm 1 slaughtered for human consumption were confirmed as positive. Consequently, all cervids — 54 elk, 41 Sika deer and 5 Albino deer — were culled, and one elk was found to be positive. Epidemiological investigation was conducted by the Veterinary Epidemiology Division (VED) of NVRQS in collaboration with provincial veterinary services.
Epidemiologically-related farms were searched for: 3 farms were found, and all cervids at these farms were culled and subjected to CWD diagnostic [testing]. Three elk and 5 crossbreeds (Red deer and Sika deer) were confirmed as positive at farm 2. All cervids at Farm 3 and Farm 4 — 15 elk and 47 elk — were culled and confirmed negative. Further epidemiological investigation showed that these CWD outbreaks were linked to the importation of elk from Canada in 1994 based on circumstantial evidence.
In December 2010, one elk was confirmed positive at Farm 5. Consequently, all cervids — 3 elk, 11 Manchurian Sita deer and 20 Sika deer — were culled, and one Manchurian Sika deer and 7 Sika deer were found to be positive. This is the 1st report of CWD in these sub-species of deer.
Epidemiological investigation found that the owner of Farm 2 in the CWD outbreaks of July 2010 had co-owned Farm 5. In addition, it was newly revealed that one positive elk was introduced from Farm 6 of Jinju-si Gyeongsang Namdo. All cervids — 19 elk, 15 crossbreeds (species unknown) and 64 Sika deer — of Farm 6 were culled, but all were confirmed negative.