TECHNIQUE

Tonsil Biopsy in Deer (Cervidae) for diagnosis of CWD (Disease Investigation & Control - Treatment and Care)

Summary Information
Type of technique Health & Management / Chronic Wasting Disease Flowchart / List of hyperlinked Techniques & Protocols:
Synonyms and Keywords --
Description Taking the sample:

The following description outlines the procedure as described by (J223.83.w1)

  • The deer is anaesthetised.
  • Once anaesthetised the deer is blindfolded and placed in sternal recumbency.
  • A metal mouth gag is used to hold the mouth open.
  • The palatine tonsil is visualised using a laryngoscope with a 30 cm blade.
  • The biopsy is collected using a 30 cm Jackson endoscopic forceps with a 4mm cup.: the cup is placed in the tonsillar crypt and pressed against the ventral-medial wall.
  • One to several tissue samples are collected.
  • Prophylactic antibiotics and analgesics are given.
  • The mouth gag and the blade of the laryngoscope are wiped with 20% bleach solution and rinsed with water.
  • The Jackson forceps are cleaned, soaked in 20% bleach solution for 30 minutes and then rinsed with water. 

(J223.83.w1)

The following description outlines the procedure as described by (J40.66.w2)
  • The deer is anaesthetised.
  • Once anaesthetised the deer is blindfolded and placed in sternal recumbency.
  • A metal mouth gag is used to hold the mouth open.
  • The biopsy is collected using a 6 mm biopsy forceps.
  • The first bite with the biopsy forceps is taken at the rostral rim of the tonsillar sinus with the biopsy forceps then rotated to take subsequent bites which include the sinus.
  • Bleeding, if it occurs, is controlled using a gauze pad and placing mild pressure on the biopsy site.

(J40.66.w2)

Appropriate Use (?)
  • For collection of tonsillar tissue to be used in the diagnosis of CWD of Deer and Elk. (J223.83.w1)
Notes
  • Repeated collection of tonsillar biopsies did not appear to reduce the success of follicle collection from a given animal. (J223.83.w1)
  • Supplementary lighting may be provided by using a head lamp worn by the operator or a small hand-held flashlight. (J40.66.w2)
  • "Proper labeling, maintaining label readability, and preventing label separation from specimens are as critical as proper specimen selection and preservation." (B36.2.w2)
Complications/ Limitations / Risk
  • Failing to direct the biopsy instrument to the ventro-medial aspect of the tonsillar crypt may result in the collection of samples which do not contain tonsillar follicles and are therefore inadequate.(J223.83.w1)
  • Samples collected using a 4 mm biopsy forceps were less likely to contain a follicle and therefore more likely to be unusable, compared to samples collected using a 6 mm biopsy forceps. (J40.66.w2)
  • Samples may be inadequate if the biopsy forceps are inserted directly into the sinus or an attempt is made to take deep bites. (J40.66.w2)
  • Requires anaesthesia, specialist equipment and a specific technique to ensure useable samples are obtained: these requirements all limit the use of tonsillar biopsy as a management tool for CWD. (P40.1.w18)
  • The requirement for immunohistochemistry for diagnostic evaluation of samples precludes the use of this test as an "on-site" or "animal-side" test. (P40.1.w18)
  • Large-scale application of this technique to free-ranging populations appears to be impractical. (N8.18.w8)

Proper regard to diagnostic procedures and disinfection should be maintained, and this technique should be read in association with:

Equipment / Chemicals required and Suppliers
  • Appropriate anaesthetic equipment;
  • Mouth gag
  • Laryngoscope (30cm blade)
  • Biopsy forceps (30cm long)
Expertise level / Ease of Use
  • Procedure should only be undertaken by an individual with appropriate clinical training and practical experience; this would usually be a veterinarian or someone with advanced veterinary technician training. (J223.83.w1)
Cost/ Availability
  • Relatively expensive. Cost per sample collected may be five or six times the cost per sample from hunter-harvested cervids. (D127)
Legal and Ethical Considerations
  • Although the agent causing CWD is not known to be infectious to humans, appropriate protective clothing including gloves should be worn to minimise the risk of any human exposure to the CWD agent. 
  • In some countries there may be legislation restricting the use of this type of technique to licensed veterinarians. For example in the UK: "The Veterinary Surgeons Act 1966 (Section 19) provides, subject to a number of exceptions, that only registered members of the Royal College of Veterinary Surgeons may practice veterinary surgery." (see: LCofC1 - RCVS Guide to Professional Conduct 2000 - Treatment of Animals by Non-Veterinary Surgeons).).

THE FOLLOWING CLASSIFICATION SHOULD BE CONSIDERED, AND BIOSAFETY LEVEL CHECKED FOR RECENT ALTERATIONS PRIOR TO COMMENCING STUDIES:

  • In the USA the following Biosafety level classifications for TSE agents are suggested in the CDC's "Biosafety in Micribiological and Biomedical Laboratories":
    • "Biosafety level classification. Human prions and those propagated in apes and monkeys are manipulated at Biosafety Level 2 or 3, depending on the studies being conducted. BSE prions are likewise manipulated at Biosafety Level 2 or 3, due to the possibility that BSE prions have been transmitted to humans in Great Britain and France. All other animal prions are considered Biosafety Level 2 pathogens. Thus, based on our current understanding of prion biology described above, once human prions are passaged in mice and mouse PrPSc is produced, these prions should be considered Biosafety Level 2 prions, even though the human prions are Biosafety Level 3 under most experimental conditions. An exception to this statement is in the case of mice expressing human or chimeric human/mouse transgenes. These transgenic mice produce human prions when infected with human prions and should be treated as Biosafety Level 2 or 3 in accord with the guidelines described above." (D131)
    • In the UK for laboratory work with the agent of CWD (as well as human TSE agents and the agents of BSE, FSE and TME), the recommended Overall Laboratory Containment Level for experimental work is level 3, with Animal Containment Level 3 for small animal work and level 1 for large animal work, although some derogations from full Containment Level 3 may be allowed (subject to local risk assessment) since transmission is considered most likely to occur percutaneously or by ingestion (to a lesser extent). (B320)
Author Dr Debra Bourne MA VetMB PhD MRCVS (V.w5)
Referee Suzanne I Boardman BVMS MRCVS (V.w6)
References J223.83.w1, J40.66.w2, P40.1.w18, N8.18.w8, D127, B36.2.w2

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