Diseases / Miscellaneous / Multi-factorial / Metabolic Diseases / Chronic Wasting Disease of Deer and Elk / Detailed Disease Description:

< > Literature Reports of POPULATION CONTROL MEASURES for CWD of Deer and Elk:

Population Control Measures

Editorial Summary (Editorial Overview Text Replicated on Overall Disease page - CWD of Deer and Elk)
  • In captive cervids all individuals on affected premises may be killed as part of CWD control.
  • In free-ranging cervids a variety of population control strategies may be used:
    • Culling of clinical suspects may be used to remove potential sources of infection.
    • Targeted removal of yearling males in infected areas may be used to reduce the risk of such animals moving the disease into a new area when they naturally disperse.
    • Aggressive depopulation may be used to decrease the risk of animals transporting the disease out of the affected area during seasonal migration or in areas in which the disease has been detected only recently, and in which the prevalence of disease within the population is relatively low, as a strategy to reduce the population, limit disease transmission and eliminate the disease from the area.
    • Population reduction may be undertaken in an area not yet affected by the disease, with the aim of reducing the risk that it will be introduced into the area. 
  • Restrictions on baiting and feeding of free-ranging cervids may be used to reduce unnatural close contact between individuals. Such contact is likely to increase the risk of transmission of CWD and other diseases.
Detailed Reports In captive cervids:
  • In one captive breeding facility: depopulation, removal of soil to a depth of one foot (30 cm), plowing of the ground, spraying of hypochlorite (Clorox) over the whole area and leaving the facility empty for one year. The disease reappeared following repopulation of the facility with deer and elk. The source is unclear. (J237.43.w1). 
  • The Kremmling Research Facility and the Foothills Wildlife Research Station were depopulated, sprayed at an application rate of 1,000 ppm with a 65% active chloride solution by mobile sprayer and by helicopter and an external fence, eight feet (2.44 m) high, was constructed before reintroduction of big game cervids was begun with 12 elk calves for hand rearing. Materials for the construction of the elk rearing units were acquired from dismantled pens from the Fort Collins Research Center [what if any disinfection was employed on these pens prior to their use was not stated]. (N9.1985.w1, N9.1986.w1)
  • Depopulation alone (Wyoming facility). Killing all elk and deer in the parts of the facility where cases had occurred and repopulating, using animals sourced from areas not recognised to have CWD, after a year. This was unsuccessful; cases recurred five years later. Potential sources of infection may have been contaminated premises or possibly shedding of the agent by other species (bighorn sheep, moose and pronghorn) which, although showing no clinical signs, had been in contact with the previous infected animals. (J64.11.w3)
  • Depopulation and disinfection (Fort Collins facility, Colorado). All deer and elk were killed and buried on site, the soil was turned, the structures and pastures were sprayed repeatedly with calcium hydrochloride and the area kept cervid-free for a year before restocking with elk calves hand-reared using evaporated milk but no other sources of animal protein. Two of 12 animals developed CWD at three to four-and-a-half years old. The source of infection was unknown; it is possible that the calves were already latently infected on arrival as they had been collected from a region in which cases of CWD were recognised subsequently.(J64.11.w3)
  • In Saskatchewan, Canada, a herd of elk on a game farm was depopulated in response to a single case of CWD. (B294.10.w10)
  • In Montana, USA all animals in the herd of elk in Philipsburg were euthanased following detection of CWD in one animal. (W27.08Nov99.cwd1, W27.12Jan2000.cwd1, W415.26Mar03.CWD3)
  • Infected farmed populations may be depopulated. (J40.66.w1)
  • Depopulation is one control option for captive cervids (the other being quarantine). (P10.67.w1)
  • In Canada as part of the national control program implemented in 2000, if a case of CWD is diagnosed on a premises, all animals which may have been in contact with the CWD-positive animal within the last 36 months are destroyed, including not only animals on the premises but also animals which left the premises within the previous 36 months. (W43.10Apr03.CWD4)

In wild cervids:

  • Modelling suggests that low selective culling rates, removing less than 20% of the affected population, could effectively eliminate CWD in an area if initiated while the prevalence of the disease was low (<1%), but that as prevalence increased the likelihood of control by culling decreased, with a dramatic decline in effectiveness of a selective culling strategy if the prevalence was 5% rather than 1% at the time when the programme was initiated. (J40.65.w1)
  • In Routt County, Colorado, where CWD-deer were detected in the area around an infected elk facility, hundreds of deer and elk were killed within a five mile radius of the infected facility, aiming to kill as many wild deer and elk as possible in this area before their seasonal migration out of the area. (N8.18.w10)
  • The Plan for Assisting States, Federal Agencies, and Tribes in Managing Chronic Wasting Disease in Wild and Captive Cervids recognises that:
    • Depopulation can be used for free-ranging cervids in limited geographical areas. (D110.w3)
    • Reduction in population density can be used as a disease control measure either where CWD is already present or as a preventative measure.(D110.w3)
    • Targeted removal may be used to reduce a specific subset of an affected population, such as yearling males which may naturally be dispersing from an area with CWD. (D110.w3)

  • Unnatural concentration of wild cervids, for example at sites where artificial feed is provided (whether as bait by hunters or feeding for watching wildlife), is likely to increase the risk of transmission of CWD (and other diseases) between individuals. (D113)

    • It has been suggested that baiting and feeding of deer and elk should be restricted or banned in areas where CWD is present in free-ranging deer and elk. (D109.w3, D109.w7, D113)

    • In Wisconsin regulations which came into effect on 11th September 2003 banned baiting and feeding in 23 southern counties of the state. In other counties, while baiting (within regulations) and feeding is not prohibited, it has been recommended that individuals restrain from feeding deer, due to the disease risks associated with concentrating deer at feed sites. (W400.Jan04.CWD2)

  • In Wisconsin, following the detection of CWD, a programme of depopulation was started in the area around where the disease had been found, with the aim of preventing transmission both within and out of the infected area and preventing shedding of the agent into the environment. An area around the proposed depopulation zone was designated for herd reduction, aiming to lower deer density to stow or prevent spread of CWD outside the area recognised as being affected. (D109.w5, D109.w5)
Technique Descriptions, if available

To Top of Page
Go to general Chronic Wasting Disease of Deer and Elk page

Authors & Referees

Authors Dr Debra Bourne MA VetMB PhD MRCVS (V.w5)
Referee Suzanne I Boardman BVMS MRCVS (V.w6)

To Top of Page
Go to general Chronic Wasting Disease of Deer and Elk page