The occurrence of variant Creutzfeldt-Jakob disease (vCJD) and the probable causal link with bovine spongiform encephalopathy (BSE) in cattle have increased interest in the search for possible environmental sources of sporadic CJD (sCJD). Presumed iatrogenic CJD is rare. Up to the year 2000 there had been 267 cases reported worldwide: three cases secondary to human corneal grafting (one confirmed, one probable, and one possible case), 114 related to human dura mater grafts, 139 related to human growth hormone treatment, four related to human pituitary gonadotrophin therapy, and seven linked to neurosurgical procedures or stereotactic EEG electrodes. (1) Because of the marked resistance of the infectious agent of CJD to conventional sterilisation techniques, there is concern about the possibility of transmission of infection via surgical instruments in contact with infected tissue, especially in neurosurgery or ophthalmic surgery.
The presence of infection in the eye in sCJD was first demonstrated following the intracerbral inoculation of pooled sCJD eye tissue in non-human primates. (2) Recently the infectious form of prion protein (Pr[P.sup.Sc]) has been identified in the neural retina, optic nerve, and in retinal pigmented epithelium in variant and sporadic CJD using immunohistochemistry or western blot, (3 4) with comparable levels to those found in brain. Pr[P.sup.Sc] was not detected in other ocular tissues. Although this suggests that there may be a greater risk of contaminating surgical instruments in procedures involving the posterior segment of the eye, infectivity has been demonstrated in animal and human cornea, (5) and circumstantial evidence has implicated corneal transplantation as a mechanism of transmission of iatrogenic CJD. (6) Experimental infection has been achieved following conjunctival installation of scrapie infectivity in mice (7) and by inoculation of an adapted agent into the anterior chamber of the eye in guinea pigs. (8)
Recently it has been shown that the experimental transmission of metallic suface bound prions is highly efficient. (9) Steel wires in contact with the brain of pre-symptomatic mice needed only 5 minutes to acquire an infectious load equivalent to the injection of a 1% homogenate of brain. Infected wires were inserted transiently into the brains of healthy mice and only 30 minutes of exposure was sufficient to result in infection. The same wires remained infective when reintroduced into another set of healthy mice. Although, to our knowledge, there have been no documented cases of CJD secondary to ophthalmic surgery other than corneal transplantation, there is a possibility that ophthalmic surgery might be a risk procedure for the accidental iatrogenic transmission of CJD.
Precautions to minimise the risks of iatrogenic transmission of CJD are vital and the Department of Health has established an incidents panel to provide advice in cases of all forms of human prion diseases in which there is the possibility for cross infection. However, an important question is …