Scalpels Called Possible Vector for Spreading vCJD

LONDON, Aug. 2 -- Surgery is a possible pathway for a self-sustaining epidemic of variant Creutzfeldt-Jakob Disease (vCJD), according to researchers here.

All of the 161 vCJD cases known in Britain so far can be blamed on eating beef infected with bovine spongiform encephalitis (BSE), and the annual incidence has been steadily decreasing since 2000, according to Tini Garske, Ph.D., of the London School of Hygiene and Tropical Medicine.

However, there is increasing evidence that some infected people can remain subclinical -- albeit infectious -- until they die from other causes.

If those people have surgery, the abnormal prior particle PrP^sc could contaminate surgical instruments and be transmitted to subsequent patients, Dr. Garske and colleagues reported online today in the Journal of the Royal Society Interface.

"Given the frequency of high- and medium-risk surgical procedures undertaken in the United Kingdom, a range of plausible scenarios suggest that surgical procedures could provide a potential route for a self-sustaining epidemic of vCJD," the researchers argued.

In a detailed mathematical analysis, Dr. Garske and colleagues argued the likelihood of such a self-sustaining epidemic depends on several key factors:

• The number of times a single instrument is re-used.
• How infectious contaminated instruments are.
• How effective cleaning and sterilization procedures are.

Unfortunately, the researchers said, little of that information is available, so that it's difficult to judge how likely it is that the vCJD epidemic could be sustained through surgical procedures. "A survey into the frequency of re-use of surgical instruments would help reducing these uncertainties," they suggested.

While instruments are routinely sterilized between procedures, the researchers said, studies published in 2001 and 2004 suggest that the PrP protein "binds strongly to stainless steel" and that standard sterilization may not work, because higher-than-standard temperatures are needed to deactivate PrP^sc.

Moreover, they noted, a survey of decontamination processes in British hospitals showed that many fell short of ideal. Despite remedial steps, they said, "it is likely that the reality of decontamination is still less than perfect and hence that residual infectivity will remain."

The mathematical model used in the study assumed that the risk of becoming infected during a surgical procedure depends only on the overall prevalence of infection on surgical instruments. But, Dr. Garske and colleagues noted, instruments used for one type of surgery are usually reserved for that type of surgery.

While that practice could increase the risk in some circumstances -- in brain or spinal column surgery, for instance -- it is more likely to reduce the overall risk to the general surgical population, they said.

They also noted that they neglected the effect of reduced survival after surgery which would lead to a reduction in transmission.

Dr. Garske and colleagues called for more data to fill out the picture. "A first step to reducing the current uncertainty in the potential for self-sustaining transmission via surgery would be to survey the frequency with which different instruments are used, particularly those used on high-infectivity procedures," they said.

Also, the tracking of surgical instruments should be improved, they said, "so that, at the very least, instruments are not re-used once the infection status of a patient is known."