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Introduction and General Information

Quarantine and disinfection are traditional techniques used in the management of disease in captive animals and in some circumstances may be appropriate for use in free-living animals.

To be effective, quarantine must effectively separate the animals under quarantine from other susceptible animals for a sufficiently long time that surveillance can demonstrate absence of the disease in the quarantined animals. In the case of CWD, due to the long incubation period, a prolonged period of quarantine, with active surveillance, would be required before it would be possible to certify a captive herd as free from the disease. See: Diagnosis and Surveillance (Chronic Wasting Disease Control) - Surveillance in farmed cervids

  • Quarantine of free-living cervids for control of CWD is unlikely to be practical, as these animals undertake migratory movements and may disperse considerable distances. However quarantine may be useful in the management of this disease in captive cervids.

Disinfection is problematic for the TSE diseases. The agent is extremely resistant to most standard means of chemical and physical disinfection. Additionally, the agent can survive in the environment for prolonged periods; exactly how long is not yet known. No techniques are known for measuring the level of CWD agent in the environment.

NOTE: At the time of writing the APHIS Project Plan for Captive Cervids (W30.23May02.CWD1) is still in draft form. The finalised plan may differ from the draft plan. 

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Captive herd Quarantine

  • Quarantine of affected herds is one option for management of CWD (the alternative being depopulation). (B209.17.w17, P10.67.w1)
  • Quarantine should be imposed on any herd in which CWD is diagnosed, prior to further actions being taken. (P41.18.w1)
  • Quarantine may be appropriate in situations where it is believed that only one or a small number of individuals on the premises are likely to be infected with CWD, for example in an elk farm where one or a small number of individuals have been acquired from a facility in which CWD has been diagnosed subsequently, or in a facility in which one case was diagnosed a considerable time ago and no cases have been diagnosed since that time. (P41.18.w1)
    • In such circumstances it may be appropriate to quarantine the herd, with all animals which die or are slaughtered being tested for CWD. If no further cases are diagnosed within five years the quarantine could be lifted.
      • "The [proposed USDA] regulatory program provides certification status for producers who maintain herds for a minimum of five years with no evidence of the disease." (D110.w3)
      • "In the light of uncertain incubation periods and variation in clinical presentation and course, a minimum of 5 years of complete surveillance of all juvenile (>6 month old) and adult mortalities seems the minimum standard necessary to provide relative assurance that farmed cervid herds do not have CWD". (J40.66.w1)
  • Quarantine might be appropriate for a zoo holding genetically valuable individuals. (J2.34.w1)
    • It must be noted that an institution under quarantine would have restrictions on movements of cervids both to an from the institution, and possibly within the institution. (J2.34.w1)
  • See: CWD CONTROL: CWD Diagnosis and Surveillance (Overview of Techniques)
  • Quarantine with or without selective culling of animals is identified as the alternative option to depopulation in the APHIS Revised Draft CWD Program Plan (W30.23May02.CWD1) Herd Certification Program Standards. Depopulation is identified as the preferred option.
    • Quarantine would continue for 60 months after the last case of CWD identified in the herd. (W30.23May02.CWD1)
    • There would be requirements for fencing of the quarantined herd to prevent fence line contact between the quarantined herd and other captive or free-living cervids. (W30.23May02.CWD1)
    • Selected animals would be euthanased, tested and disposed of, with CWD-positive animals disposed of according to USDA guidelines for such disposal . (W30.23May02.CWD1) See: CWD of Deer and Elk Culling and Carcass Disposal
    • Monthly herd inspection would be conducted by State or Federal personnel with removal and CWD testing of any suspect animals. . (W30.23May02.CWD1)
    • There would be an inventory, with individual animal identification and annual verification of the inventory by State or Federal veterinarians. . (W30.23May02.CWD1)
    • During the quarantine there would be herd surveillance with mandatory death reporting and CWD testing of animals of all ages; this would continue for 60 months from the last case. (W30.23May02.CWD1)

Examples of situations in which quarantine has been used:

  • Following detection of CWD in a single seven-year-old bull elk in Korea, which had been imported from Canada, quarantine and monitoring, including examination of all dead cervids from the premises for CWD, has been instigated for other premises which have received elk from the same source farm in Canada. (J27.64.w1)
  • Following detection of CWD in one captive elk bull in Minnesota and depopulation of the remainder of the herd (all were found to be CWD-negative) two facilities in which the bull had previously resided were placed under quarantine, with importation and exportation of elk prohibited "indefinitely while an epidemiological investigation is being conducted." (W414.10Apr03.cwd1)
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Fencing requirements

There is a risk that disease, including CWD may be transmitted from captive to wild cervids, or vice versa, across fencing. (P10.57.w1, P10.67.w2)
  • Double fencing and frequent inspection of fences could be used to minimize or eliminate the potential for physical contact between wild and captive cervids. (W414.10Apr03.CWD1)
    • Single fencing allows direct contact between wild and captive cervids, which increases the risk of disease transmission. 
  • The APHIS Revised Draft CWD Program Plan (W30.23May02.CWD1) Herd Certification Program Standards states that "States shall have perimeter fencing requirements adequate to prevent ingress or egress of cervids." (W30.23May02.CWD1)
    • It was noted that fencing is designed to reduce the risk of transmission from captive elk to free-living cervids and vice versa. (W30.23May02.CWD1)
    • In areas where CWD is endemic in free-ranging populations of cervids, double fencing is strongly recommended. (W30.23May02.CWD1)
    • If a captive herd is identified to be CWD-positive, double fencing shall be required. (W30.23May02.CWD1)
  • Captive research facilities containing CWD-positive cervids could potentially act as a source of CWD for cervids in the surrounding area. (D114.III.w3)
    • Double fencing of captive research facilities containing CWD-positive cervids is important to reduce any chance of close contact between cervids within the facility and those outside, and to minimise chances that cervids could get into or out of such facilities.
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Policy regarding captive cervids escaping from farms

There is a risk of transmission of disease from captive to free-ranging cervids if infected animals escape from a cervid farm. (P10.57.w1)
  • In order to minimise the risk that CWD will be transmitted from farmed to wild cervids via escaped animals regulations are required which state categorically that farmed cervids may not be released and that if a cervid escapes it must be reported to the relevant agency promptly (e.g. within 24 hours).

(D121)

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Policy regarding free-ranging cervids entering farms

There is a risk of transmission of disease from captive to free-ranging cervids [or vice versa] if free-ranging animals enter a captive facility and then leave it again. (P10.57.w1)
  • At least one farm has been documented in which CWD was detected in farmed animals and was subsequently detected in originally free-living white-tailed deer which had become confined when the farm area was fenced. Approximately 50% of the confined publicly-owned white-tailed deer were found to be CWD-positive and a lower percentage of free-living deer in the area around the farm were also found to be positive for the disease. (N8.18.w10)

In order to minimise the risk of transmission from farmed cervids to free-living cervids via free-living cervids entering and leaving premises, it has been suggested that wild cervids entering the confined area of a facility for farmed cervids should be culled by the owner of the facility and reported to the relevant authority promptly (e.g. within 24 hours). (W414.10Apr03.cwd1)

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Policy regarding rescued/rehabilitated cervids

  • In Wisconsin it has been recommended that: (W399.21May03.CWD2)
    • Orphaned fawns and sick/injured deer from CWD affected counties should be humanely euthanased rather than hand-reared or rehabilitated. 
    • Healthy "rescued" deer in Dane, Iowa and Sauk counties must be euthanased, followed by testing for CWD if the animal is over 18 months old or originating from the core CWD-affected area.
    • Carcasses of such animals should be incinerated or disposed of in a managed landfill.
    • For the rest of the state: 
      • Rehabilitated deer should be identified with a tattoo on the inside of the left ear and released within their county of origin, preferably within the immediate area in which they were found.
      • Deer cannot be transported to CWD-affected counties for rehabilitation.
      • Sick deer showing signs compatible with CWD should be euthanased and submitted to the Wisconsin DNR for testing
      • If temporary holding of such sick deer is required this should not take place in a facility or crate which will be used for other deer and the deer should be kept separate from other deer.
    • Orphaned deer "will not be sold or given to WI licensed deer farmers." It is noted that such placement would violate the present emergency order and proposed permanent rule of the Wisconsin Department of Agriculture Trade and Consumer Protection restricting movement of cervids between deer farms unless they are entered into a CWD monitoring program. Placing orphaned fawns into deer farms would defeat the purpose of a CWD monitoring program and require the farm to be placed under quarantine. 

      (W399.21May03.CWD2, V.w50)

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Role of Environmental Contamination

Environmental contamination appears to play a role in the maintenance of CWD, at least in captive populations. This has been indicated by the recurrence of CWD in facilities following complete depopulation and subsequent repopulation, even when repopulation was carried out from a certified CWD-free herd. (P41.18.w1).

  • It is not yet known to what extent environmental contamination is important in the transmission of CWD in free-ranging populations.

    • "A major concern with CWD is the potential for indirect transmission through contamination of the environment through excretions, secretions, or the decomposition of infected animal carcasses." (D110.w3)

    For further information see: Prion Protein Literature Reports: Transmission (Chemical Reports)

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Sources of Environmental Contamination
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Disinfection of knives and other implements

Disinfection of implements for control of CWD is complicated by the nature of the agent, which is extremely resistant to chemical disinfectants as well as to physical methods of inactivation.
  • "The causal agents of the TSEs are collectively recognized to have the potential for extended survival in the environment and to be resistant to many, but not all, processes that are traditionally used for the inactivation of conventional microorganisms." (P40.1.w43)

Most commonly used disinfectants are not effective against the TSE agents.

Suggested methods of disinfecting knives and other implement which have been used e.g. for butchering deer are:

  • Sodium hypochlorite (household bleach, greater than 2% free chlorine) at 280 ml in 720 ml of water at room temperature, for one hour. This solution may be corrosive to metal utensils. (J40.66.w1)
  • Sodium hydroxide (caustic soda, soda lye) at 38g in one litre of water at room temperature for one hour. This solution may be corrosive to metal utensils. (J40.66.w1)

Information about physical and chemical methods of deactivating the agents of TSEs are provided in:

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Disinfection of buildings and other enclosures 

Disinfection of premises for control of CWD is complicated by the nature of the agent, which is extremely resistant to chemical disinfectants as well as to physical methods of inactivation. 
  • Disinfection programs against transmissible disease agents may fail due to inadequate cleaning, use of compounds which are ineffective, excessive dilution (past the optimal concentration), use at temperatures too low for optimal activity. (B21)
    • It is still not known whether contaminated environments contaminated with TSE agents can ever be completely disinfected. (N8.18.w8)
  • Apparent failure of disinfection programs may also occur as a result of reintroduction of the infectious agent by carrier animals, rodents, insects or other animals, food or fomites. (B21)
    • It is likely that residual environmental contamination was responsible for the failure of two attempts to eradicate CWD from wildlife research facilities. (N8.18.w8, , P10.67.w1)

Information about different chemical disinfectants is provided in:

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Disinfection of Large areas

  • At the present time there does not appear to be a practical way of disinfecting large areas in order to deactivate the CWD agent.
  • To date destocking and disinfecting CWD-infected premises, followed by restocking after an interval of time, has not been successful in eliminating the disease on the premises. The reasons for such failures are not known.
  • Further research is required to determine how effective disinfection of large areas (e.g. deer or elk farms) can be carried out. (D110, D121)

(J2.34.w1, J40.66.w1, P10.67.w1)

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Time required for quarantine restrictions and disinfection BEFORE restocking

At the present time the length of time for which a premises must be left, after depopulation and disinfection, before restocking, it is not certain.
  • It has been suggested that until effective cleaning and disinfection procedures are identified, it would be prudent to refrain from reintroducing captive cervids into commercial facilities where CWD has occurred, and to exclude free-ranging cervids from previously-infected premises. (J40.66.w1, P10.67.w1)

Further research is required on this topic.

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Policy regarding quarantine and disinfection in zoos

  • It is recommended that the presence of free-ranging cervids in the grounds of zoos should be strongly discouraged and that appropriate methods of excluding wildlife, for example perimeter fences, should be used to minimise contact of wildlife with animals in the collection. (J2.34.w1, W253.Jun03.CWD1)
  • The AAZV Infectious Disease Committee has drafted guidelines for AZA-accredited institutions regarding CWD. Within these it notes that "Until effective cleaning and disinfection protocols can be identified, it is recommended that cervids should not be introduced to facilities or exhibits where CWD has occurred for at least 5 yrs. It is also critical that free-ranging cervids and other wildlife be excluded from these areas." (W253.Jun03.CWD2)
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Further research

For effective management of CWD it will be necessary to develop a better understanding of this disease, including:
  • How CWD spreads between cervids within a species and between cervid species (transmission routes); (D114.V.w5, D117, D121, P50.1.w7)
  • Whether CWD has the capability to spread to other species such as cattle, sheep, goats, carnivores and humans; (D114.V.w5, D117, D121)
  • The effect of animal density on CWD prevalence and transmission. (D117)
  • The effects of animal movement and behaviour on CWD transmission and spatial distribution. (D117)
  • The persistence of the CWD agent in the environment. (D110)
  • The role of environmental contamination in maintaining CWD in captive facilities and in free-ranging populations; (D114.V.w5, D117, D121)
  • Methods for inactivation of the CWD-agent in the laboratory and in the field. (D110, D121)
  • Adequate cleaning and disinfection approaches for contaminated premises.(P50.1.w7)
  • Methods for measuring levels of CWD agent in the environment. (P50.1.w7)

N.B. Results of research must be distributed effectively if they are to be of benefit to agencies responsible for disease management.

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Authors & Referees

Authors Dr Debra Bourne MA VetMB PhD MRCVS (V.w5)
Referee Suzanne I Boardman BVMS MRCVS (V.w6), Chris Brand (V.w52), Dr Terry Kreeger (V.w49), Dr Julie Langenberg (V.w50), Bruce Morrison (V.w48), Michael Samuel (V.w53), Scott Wright (V.w54)

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