Page updated 9 October 2006
Instrument Decontamination and vCJD
Decontamination of instruments used on patients with TSE (Transmissible Spongiform Encephalopathies)
Key points:
1. Dental procedures classified as low risk for transmission of CJD or vCJD.
2. In order to prevent cross infection and onward transmission of vCJD via endodontic instruments it is recommended that these instruments should be single use only.
3. Patients identified at risk or their relatives should not be refused routine dental treatment
4. Ensure that satisfactory standards of decontamination are observed
5. Information about patients who are at risk of vCJD is included in any referrals for surgery and recorded in your records
Dentistry and vCJD
The risk of transmission of CJD or vCJD from dental instruments is thought to be very low, provided that best practice guidelines for infection control and national standards on decontamination are followed.
The current advice issued by the Department of Health is that reusable instruments used on known, suspected or at risk patients with CJD (see table 13) or their relatives can be re-processed using standard, optimal decontamination procedures and returned to use ( as outlined in these Guidelines). No additional infection control precautions are required when treating these patients for routine dental treatment.
Therefore there is no reason why any categories of patient defined in table below or their relatives should be refused routine dental treatment. Such people can be treated in the same way as any member of the general public. It is most unlikely that a confirmed case of sporadic CJD or vCJD would present at a GDP surgery due to the dehabilitating nature of the disease. Therefore the cross infection risk arises in relation to unidentifiable asymptomatic carriers of the vCJD and those who are at potentially at an increased risk of the disease due to iatrogenic exposure from vCJD contaminated blood transfusions and plasma products.
Prevalence of vCJD in the UK
Transmissible Spongiform Encephalopathies (TSE) are a group of rare, fatal degenerative central nervous system infections, which occur as sporadic, familial or acquired disease. The TSEs are caused by prions (infectious protein particles), which are an abnormal pathogenic form of a human cell surface protein known as PrP. The commonest TSE is the sporadic form of Creutzfeldt-Jakob disease (CJD) with an incidence of 1 in a million /population per annum. TSEs have a long asymptomatic incubation period lasting a decade or more before the appearance of clinical disease.
In the UK , vCJD was first diagnosed in humans in 1996 and was linked to the consumption of meat products tainted with bovine Spongiform Encephalopathy (BSE or "mad cow disease"). vCJD differs from sporadic CJD in that it affects younger people, has a shorter incubation period, with prominent early psychiatric and behavioural manifestations and persistent parathesias. Up to June 2006, the total number of reported cases of confirmed or probable vCJD in the UK is 161 patients of which 6 are still alive. The exact number of people incubating the disease is unknown. A study reporting in 2004 examined tonsils and appendices removed during surgery on over 12,000 patients resident throughout the UK , demonstrated abnormal prion protein in 3 cases, which after extrapolation gives an estimated 3,800 preclinical cases across the UK . Theoretically, during the preclinical stage of the disease vCJD carriers could transmit infection to other patients via inadequately decontaminated surgical instruments.
Iatrogenic transmission CJD and vCJD
Available epidemiological evidence suggests that normal social or routine clinical contact with a patient suffering from any type of CJD (Creutzfeldt-Jakob disease) including v CJD does not represent a risk to healthcare workers. However, a number of cases of iatrogenic CJD have been associated with the administration of hormones prepared from human pituitary glands and dura mater grafts and three cases have been reported associated with corneal grafts. Transmission has also been identified following neurosurgical procedures with inadequately decontaminated instruments.
Blood components and plasma products
Two reports of possible transmission of vCJD through blood transfusion were announced in December 2003 and July of 2004. The cases had received blood from donors who were well at the time of donation but later died of vCJD. The second of these patients died of causes unrelated to vCJD but the post-mortem revealed vCJD in the spleen, indicating that the patient had been infected with vCJD. The possibility that vCJD can be transmitted through blood raises concern about the possible infectivity of blood components and plasma products. Certain patients with bleeding disorders (e.g. haemophilia, Von Willebrand disease and antithrombin III deficiency) and a small number of others who were recipients of specific plasma products (e.g. clotting factors and antithrombin sourced between 1980 and 2001) have been identified and will be informed by their doctor that from a public health safety standpoint, they are deemed to be at an increased risk of vCJD. This group of patients have been asked to notify their dentist of their risk status. The dentist will then be able to ensure that satisfactory standards of infection control are used.
Dentists are recommended to include this information in referral letters for invasive surgical procedures to specialists such as maxillofacial surgeons as additional infection control procedures are required for surgery that could involve the lingual tonsil or other organs and tissues potentially infected with vCJD. But as far as dental treatment is concerned such patients can be managed in the same way as any other member of the public and should not be refused routine care in dental practice. However, the possibility of transmission via blood transfusion does emphasize the need for every precaution must be taken to ensure optimal standards of infection control and instrument decontamination are employed in the practice.
Adapted from CDO letter 4 th February 2005, Gateway reference Number 4463 entitled "Information for dentists about the management of patients with, or at risk of, Creutzfeldt-Jakob Disease (CJD) including variant CJD (vCJD)" www.dh.gov.uk
Single use of endodontic files- Position statement from SEAC (www.seac.gov.uk)
Prions may not be inactivated by standard sterilisation procedures nor can they can they be reliably destroyed by prolonged sterilisation times (18 minutes at 134 o C). Hence, expert advice suggests that effective cleaning of instruments prior to sterilisation is of the utmost importance in reducing the risk of transmission of prions via surgical procedures. This is because the first round of cleaning of an instrument reduces contamination by approximately 100-1000 times .
Variant CJD have been recovered from brain, trigeminal ganglion, and tonsil in the examined post-mortem cases. Abrasion of the lingual tonsil is considered a highly unlikely event during routine dental treatment but could occur during maxillo-facial procedures. Fortunately, to date there are no published cases or epidemiological evidence directly linking vCJD or other TSEs to dental treatment .
Evidence suggests that the files and reamers used in endodontic procedures continue to be reused and are difficult to reliably decontaminate. Appreciable quantities of residual material remain adherent to the surface after normal cleaning and sterilisation. Thus, there is potential for transfer of dental pulp between patients undergoing endodontic procedures.
Dental pulp includes blood and peripheral nerve tissue known to carry vCJD infectivity. In addition, appreciable infectivity has been found in the dental pulp of hamsters with hamster scrapie. Although it is possible that the peripheral nerve may only become infective close to, or after, the onset of clinical vCJD, inflammation may promote the propagation of prions.
It is reasonable to assume that the dental pulp of individuals subclinically-infected with vCJD may be infectious although the level of infectivity is unknown.
There is evidence to suggest that individuals infected with the vCJD agent may remain in a subclinical infection carrier state instead of developing vCJD. They could over the course of their lives be potential sources of numerous secondary infections arising from invasive medical or dental procedures. Residual dental pulp on endodontic files and reamers is considered to be transferred relatively efficiently to patients on reuse. There is reason to believe that dental pulp is as infective as peripheral nerve tissue for v CJD in this subclinical vCJD carrier population. So potentially a self-sustaining vCJD epidemic arising from endodontic surgery is plausible.
Interactions between this and other routes of secondary transmission, such as blood transfusion and hospital surgery, would make a self-sustaining epidemic more likely.
Risk reduction measure
Therefore restricting endodontic files and reamers to single use would prevent potential secondary transmission via these instruments
Risk groups for CJD and vCJD
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Symptomatic patients |
Fulfil the diagnostic criteria for definite, probable or possible CJD or vCJD Patients with neurological disease of unknown aetiology, but where the diagnosis of CJD is actively considered |
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Asymptomatic patients at risk from familial forms of CJD linked to genetic mutations |
Patients with 2 or more blood relatives affected by CJD or a relative with a genetic mutation indicative of familial CJD Patient shown by genetic testing to be at significant risk of developing CJD or other prion disease |
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Asymptomatic patients potentially at risk from iatrogenic exposure |
Recipients of hormones derived from human pituitary gland e.g. growth hormone, gonadotrophin, or received dura mater graft before August 1992 for spinal surgery for a tumour or cyst Patients contacted as potentially " at risk" because of exposure to instruments or to blood, plasma derivatives, organs or tissue from patients who later developed CJD or vCJD |
(See the HPA website for vCJD and Plasma Products-Clinical Information). For additional information view the Guidance from the Advisory Committee on Dangerous Pathogens and Spongiform Encephalopathy Advisory Committee. Part 4: Infection Control of CJD and related disorders in the healthcare setting.
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If you have any concerns regarding decontamination or other matters prior to commencing treatment on a patient in one of the at risk categories, please contact the Health Protection Nurse or the Consultant in Communicable Disease Control either via your local PCT or regional Health Protection Agency office see www.hpa.org.uk for local contact details.
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