MemorandaI Memorandums

Public health issues and clinical and neurological characteristics of the new variant of Creutzfeldt-Jakob disease and other human and animal transmissible spongiform encephalopathies: Memorandum from two WHO meetings*

The transmissible spongiform encephalopathies (TSEs) include bovine spongiform encephalopathy (BSE), which was first described in 1986 in cattle in the United Kingdom, but has occurred subsequently also in other countries, and Creutzfeldt-Jakob disease (CJD) in humans, which is rare but with a worldwide distribution. Recently a new variant form of CJD, with a characteristic clinical and pathological phenotype, has been identified in the United Kingdom in a series of 11 young patients. This Memorandum reports the findings of two WHO Consultations. The first, held on 2-3 April 1996, issued conclusions and recommendations on certain animal products in order to protect the health of consumers. The second, held on 14-16 May 1996, examined, inter alia, the findings associated with the new variant of CJD, compared these findings with those for other TSEs, andproposed a protocol for the diagnosis and surveillance of CJD and related diseases.

Introduction variant of Creutzfeldt-Jakob disease (CJD); to com- pare these findings with those of other transmissible At a WHO Consultation held in Geneva on 2-3 spongiform encephalopathies (TSEs)a and examine April 1996 a group of international experts reviewed the putative relationship between human TSE and the public health issues related to bovine spongiform animal spongiform encephalopathies; to propose a encephalopathy (BSE) and issued recommendations protocol for the diagnosis and surveillance of CJD on various cattle products and by-products in order and related diseases; and to review the tests devel- to protect the health of consumers. As a follow-up, a oped for early diagnosis of TSEs and make recom- second Consultation was held in Geneva on 14-16 mendations for further research. May 1996 to examine the clinical, neurological, and neuropathological findings associated with a new Bovine spongiform * This Memorandum is based on the reports of two WHO Consul- tations: Report of a WHO Consultation on public health issues encephalopathy related to human and animal transmissible spongiform encephalopathies, Geneva, 2-3 April 1996 (unpublished docu- Background ment WHO/EMC/DIS/96.147); and Report of the WHO Consulta- tion on clinical and neuropathological characteristics of the new BSE is a transmissible spongiform encephalopathy vartiant of CJD and other human and animal transmissible that was first identified in the United Kingdom in spongiform encephalopathies, Geneva, 14-16 May 1996 (unpub- 1986. Transmission of BSE to cattle appears to have lished document WHO/EMC/DIS/96.148). Lists of participants are given on pages 462-463. Requests for reprints should be sent to Dr F.-X. Meslin, a TSE is a term for a group of diseases associated with a transmis- Disease Surveillance and Control, Division of Emerging and other sible agent, the nature of which is not fully known. The agent Communicable Diseases Surveillance and Control, World Health displays many virus-like features, such as strain variation and Organization, 1211 Geneva 27, Switzerland. A French translation mutation, but differs from conventional viruses in being exception- of this article will appear in a later edition of the Bulletin. ally resistant to heat, ultraviolet and ionizing radiation, and to Reprint No. 5726 chemical disinfectants.

Bulletin of the World Health Organization, 1996, 74 (5): 453-463 X World Health Organization 1996 453 Memorandum

been via contaminated meat and bone-meal in con- A study in cattle has revealed that 1 g of BSE- centrate feed (sheep or cattle may have been the infected cow brain is sufficient to cause BSE in a cow original source of the agent). The epidemic in the by the oral route. A comparative bioassay in cattle United Kingdom (the only country with a high inci- and mice provisionally shows the titre measured in dence of BSE) appears to have been due mainly to mice is 100-1000 times lower than that measured in the recycling of affected bovine material to cattle cattle. Spleen and lymph node pools administered before the July 1988 ruminant feed ban became intracerebrally (i.c.) have not transmitted BSE to effective. mice, and cows inoculated with such pools remain The epidemic of BSE in the United Kingdom is alive for twice the incubation period of those inocu- progressively declining in response to the control lated with a 1/10 dilution of brain tissue. measures. Other countries with indigenous cases of BSE are Ireland (126 cases), Switzerland (210), France (18), and Portugal (35). Seven species of captive wild Bovidae and 18 animals in all have Neuropathological aspects of the succumbed to spongiform encephalopathies (SEs) new variant of CJD via the same feed source as cattle. Domestic cats A new variant form of CJD, with a characteristic (71), puma (3), ocelot (2), and cheetah (4) have de- clinical and pathological phenotype, has been identi- veloped feline SE; the wild cats were probably in- fied in the United Kingdom in a series of 11 young fected after consuming BSE-infected tissues from patients. The characteristic neuropathological fea- the central nervous system (CNS) of cattle. Unsuc- tures are the presence of large numbers of -type cessful attempts have been made to transmit BSE to PrP-positive amyloid plaques surrounded by a halo hamsters and chickens but it has been transmitted to of spongiform change in the cerebral cortex (particu- cattle, sheep, goats, pigs, marmosets, mink and mice larly the occipital lobe), thalamic gliosis, and exten- by parenteral challenge. sive deposition of PrP in all grey matter regions, Experimental oral transmission has been at- particularly the cerebellum (including the molecular tempted in all these species except marmosets and layer); spongiform changes are most evident in the has been successful in all except pigs, with longer basal ganglia. These cases share an early age at onset incubation periods than following parenteral chal- of symptoms, an unusual clinical course, with early lenge, despite much larger doses being used. Pigs psychiatric features and a prolonged duration of ill- remain healthy nearly 6 years' post-challenge and ness, all characteristics which had not been previ- tissues from a 2-year interim kill (which did not show ously reported in the United Kingdom. One similar clinical or pathological evidence of SE) did not trans- case has recently been confirmed in France. Com- mit BSE to mice. The BSE agent is different from cases over 200 in any known strains of historical or contemporary parison of these with CJD cases the and retains its biological characteristics fol- United Kingdom Surveillance Project, which covers lowing natural or experimental passage through six also historical CJD cases, and with cases in other species, despite their different PrP gene sequences. European Surveillance Projects, has failed to iden- The BSE agent from nine different cattle sources is tify any similar cases. biologically identical. The only tissues from clinically affected confirmed cases of BSE that have shown infectivity are the brain, retina, cervical and terminal Immunocytochemical detection of spinal cord, and in experimentally orally challenged cattle during incubation, the distal ileum, which protein in CJD is consistently infected from 6-18 months' post- A total of 179 cases of sporadic CJD have been challenge inclusive. No infectivity has been found in confirmed by immunocytochemical detection of muscle (meat), milk, mammary gland, placenta, prion protein (PrP) with both monoclonal and bone marrow or peripheral nerve from clinical cases polyclonal antibodies on paraffin sections of various and over 40 other tissues. brain regions pretreated by hydrated autoclaving. Nine studies (6 experimental and 3 epidemio- PrP deposition patterns included fine granular logical) have examined the possibilities for maternal labeling of synaptic type (in about 90% of cere- transmission. The conclusions of these studies are bral and cerebellar cortical specimens), patchy/ that maternal transmission cannot be excluded but perivacuolar deposits (mostly (38%) in cerebrum), if it is occurring it is at a low and undetectable and plaque deposits (mostly (25%) in cerebellum). incidence. No closed herd study has been under- Types of deposition and amount of immunoreac- taken to clarify these aspects, but a cohort study is tive PrP varied between cases but remained rela- under way and will be completed early in 1997. tively constant between different regions of an

454 WHO Bulletin OMS. Vol 74 1996 Creutzfeldt-Jakob disease and transmissible spongiform encephalopathies individual brain. The brain stem was only involved Europe infrequently (21% with PrP deposits). PrP immu- nocytochemistry is a very reliable diagnostic tool Austria. Between 1969 and 1995, a total of 80 cases and detects a limited range of characteristic types of CJD were confirmed. The annual incidence has of PrP deposition that is relatively uniformly increased in recent years (1969-85: 0.18 per million; distributed in an individual brain. Presence of 1986-94: 0.67 per million; 1995: 1.25 per million), Alzheimer-type brain amyloid may modify PrP probably reflecting improved awareness about the deposition. condition and better diagnosis rather than a real increase in incidence. No cases of BSE have been reported in Austria. Phylogenetic analysis of prion Germany. Systematic surveillance of CJD has been disease carried out since June 1993, and based on the criteria A study of the prion protein is being undertaken of the European Union CJD Surveillance Group, to identify major trends in its evolution by means 63 probable and definite cases were recorded in of a comparative analysis of healthy prion genes. 1994 (incidence, 0.77 per million), and 64 cases Genetic differences among species, as well as genetic in 1995 (0.78 per million). The clinical and patho- polymorphisms within species, may prove valuable logical features of the new variant form of CJD have in understanding the nature of the species barrier, not been observed in Germany. A study of more and the more likely routes of transmission of the than 150 cases of CJD and the same number of con- TSEs. trols has not indicated occupational or other risk factors.

Ireland. Based on death-certificate data, there have CSF protein marker detection test been 17 deaths from CJD since 1980, two involving A simple, rapid cerebrospinal fluid (CSF) test individuals aged under 48 years. Since 1989, there has recently been developed that should prove a have been 126 cases of BSE (annual incidence, 17 useful aid in confirming the clinical diagnosis of a cases), approximately a third involving animals im- spongiform encephalopathy, human or animal. The ported from the United Kingdom. sensitivity and specificity of this test are high, and further validation studies are in progress. For exam- ple, studies are being performed to determine the Latin America test's reliability in BSE-affected cattle and patients with the newly recognized variant form of CJD and Argentina. Over the period 1980-96, a total of to clarify the association of proteins with these 30 patients with CJD were confirmed neuro- diseases. pathologically. No cases of Gerstmann-Straussler- Scheinker (GSS) disease or of fatal familial insomnia (FFI) have been reported. There is no official sur- National reports on CJD and other veillance of CJD, although there is surveillance of related disorders BSE and scrapie. No case of BSE has been reported. Brazil. In each region of the country 1-2 cases of Eastern Mediterranean CJD have been reported over the last 5 years. No in Tunisia if we increase has occurred in the number of cases of clas- Tunisia. CJD is rare and sporadic sical CJD and there have been no cases of the new exclude the high incidence of CJD reported in Israel of among Jewish immigrants of Tunisian origin. Since variant form of CJD. There is no surveillance 1980 a total of 11 cases have been reported, but in CJD. view of the difficulty in diagnosing the condition the true incidence is probably higher. Surveillance of Chile. Over the period 1964-86, a total of 69 cases of CJD and a CJD registry should be established, and CJD were reported (38 females, 31 males): 78.3% collaboration with veterinary authorities should were sporadic and the mean age at death was 55.4 be set up to study the epidemiology of scrapie and years (range, 23-75 years). Over the last 10 years, the possible relationship between CJD and animal 22 neuropathologically confirmed and 25 probable spongiform encephalopathies in the country. cases have been reported.

WHO Bulletin OMS. Vol 74 1996 455 Memorandum

Mexico. Biopsies are not carried out on most of the have been no cases that fulfil all the criteria for the probable or possible case of CJD and no docu- new variant form of CJD, but cases that meet some mented cases of GSS or FFI have been reported. of them have occurred. The absence of BSE and Despite surveillance for BSE and scrapie no cases scrapie in Australia and New Zealand makes the have been reported. epidemiological surveillance of CJD in these coun- tries an important source of information for assess- Uruguay. Some cases of sporadic CJD and of GSS ing the zoonotic risk of these diseases. have been reported. No surveillance of CJD is car- ried out but there is no evidence for an increase in its Japan. Since 1979 analysis of the incidence of CJD incidence, and no atypical cases have been reported. has been carried out based on death certificate infor- Venezuela. No surveillance of CJD is carried out, mation. Over the period 1987 to 1990 a total of 216 but possible and probable cases have been reported; cases of CJD occurred among those aged 15 years there have been no atypical cases. Cases of GSS have and older. To date there have been no cases of not been reported. the new variant form of CJD in Japan. A na- tional surveillance project on CJD and related dis- South-east Asia eases, covering 3400 hospitals with neurological/ psychiatric facilities, was established in 1996; the India. A total of 30 cases of CJD were reported in results will be reported by March 1997. Although India in 1990, with no cases of V-CJD. Approxi- no cases of BSE have been reported in Japan, a mately 15 cases have occurred in the Bombay area surveillance system for BSE as well as scrapie was set over the last 20-25 years, and of the six that were up in March 1996. autopsied two were vegetarians. Also, one case ex- hibited characteristics typical of GSS. There is no Thailand. There are no official statistics on the inci- definite evidence that scrapie occurs in Western dence of CJD in Thailand, but it is estimated that India. there have been no more than 25 cases over the last 20 years, all similar to the classic sporadic pattern in Sub-Saharan Africa terms of age of onset, clinical presentations, EEG changes and duration of illness. Senegal. CJD and related disorders are exceptional in sub-Saharan Africa; in Dakar, Senegal, only one case has been reported since 1976. Nevertheless, many factors exist for the potential establishment of a TSE; for example, in Senegal the use of neurosur- Conclusions and gical interventions (including dura-mater grafts); use recommendations of non-disposable material for biopsies and lumbar taps; and the import of meat products from countries where TSEs of sheep and cattle may exist. In Senegal Recommendations for public health the low recorded incidence of CJD and other similar During the Consultation held on 2-3 April, the conditions may be explained, inter alia, by the fol- recommendations shown below were made for the lowing: the absence of surveillance and control; the protection of public health. low level of use by the general population of quali- fied medical practitioners; the small number of * No part or product of any animal that has shown neurospecialists; and the underrepresentation of at- signs of a TSE should enter any food chain (human risk age groups in the general population, with over- or animal). In particular, the following should be 60-year-olds comprising only 3% of the total. noted: No cases of scrapie or of BSE have been re- corded in Senegal. - all countries must ensure the killing and safe dis- posal of all parts or products of such animals so Western Pacific that TSE infectivity cannot enter any food chain; and Australia and New Zealand. The annual incidence of - all countries should review their rendering proce- CJD is approximately 1 case per million, with a de- dures to ensure that they effectively inactivate mographic profile similar to that in Europe and TSE agents. North America. An atypical cluster of cases related to exposure to gonadotrophin of human pituitary * All countries should establish continuous surveil- origin has, however, been reported. To date there lance and compulsory notification for BSE based

456 WHO Bulletin OMS. Vol 74 1996 Creutzfeldt-Jakob disease and transmissible spongiform encephalopathies on the recommendations of the International Ani- The risks at present associated with exposure to mal Health Code of the Office International des the BSE agent from beef and beef products will be Epizooties (OIE). minimized if the recommendations of the present consultation are implemented. In the absence of surveillance data the status of a country with respect to the occurrence of BSE * Risks from medicinal products and medical de- must be considered as unknown. vices containing bovine tissues are as follows: * Countries should not permit tissues that are likely - the importance is reiterated of obtaining bovine to contain the BSE agent to enter any food chain materials destined for the pharmaceutical indus- (human or animal). try only from countries that have a surveillance system in place and which report either no or * All countries should ban the use of ruminant tis- only sporadic cases of BSE; sues in ruminant feed. - removal and inactivation procedures contribute * With respect to specific products, the following to the reduction of the risk of infection but it apply: must be recognized that the BSE agent is remark- ably resistant to milk and milk products, even in countries with a physico-chemical procedures high incidence of BSE, are considered safe. that destroy the infectivity of common microor- There is evidence from other animal and human ganisms; spongiform encephalopathies to suggest that - measures recommended to national health au- milk does not transmit these diseases; thorities to minimize the risk of transmitting the agent causing BSE via medicinal products, in par- gelatin in the food chain is considered to be safe ticular parenteral products, that were developed if produced by a manufacturing process utilizing at a previous WHO Consultation in 1991 con- production conditions that significantly inacti- tinue to be generally applicable;b and vate any residual infectivity that may have been present in source tissues; and - it is recommended that these measures be re- viewed and, if necessary, strengthened as more tallow is similarly considered safe if effective ren- information becomes available. dering procedures are in place.b * The risk, if any, of exposure to the BSE agent in countries other than the United Kingdom is con- Clinical and neuropathological criteria for sidered lower than that in the latter country. Expo- the diagnosis of clinical CJD and other sure to the BSE agent in the United Kingdom was human TSEs likely to be higher prior to introduction of the cur- CJD classically occurs as a rare disorder with rent BSE regulations. worldwide distribution (approximate incidence: 1 b Selected references: Brown P, Rohwer RG, Gajdusek DC. Slow virus diseases of animals and man. Amsterdam, North- Newer data on the inactivation of scrapie virus or Creutzfeldt- Holland, 1976: 243-266; Pocchiari M et al. Can potential hazard Jakob disease virus in brain tissue. Journal of infectious diseases, of Creutzfeldt-Jakob disease infectivity be reduced in the produc- 1986, 153: 1145-1148; Di Martino A et al. Purification of non- tion of human growth hormone? Inactivation experiments with the infectious ganglioside preparations from scrapie-infected brain tis- 263K strain of scrapie. Archives of virology, 1988, 98: 131-135; sue. Archives of virology, 1992, 124: 111-121; Diringer H, Pocchiari M et al. Combination ultrafiltration and 6M urea treat- Kimberlin RH. Infectious scrapie agent is not as small as recent ment of human growth hormone effectively minimizes risk from claims suggest. Bioscience reports, 1983, 3: 563-568; Hunter potential Creutzfeldt-Jakob disease virus contamination. Hormone GD, Millson GC. Studies on the heat stability and chromato- research, 1991, 35: 161-166; Taguchi F et al. Proposal for a graphic behaviour of the scrapie agent. Joumal of general micro- procedure for complete inactivation of the Creutzfeldt-Jakob dis- biology, 1964, 37: 251-258; Hunter GD. Progress toward the ease agent. Archives of virology, 1991, 119: 297-301; Tamai Y, isolation and characterization of the scrapie agent. In: Gajdusek Taguchi F, Miura S. Inactivation of the Creutzfeldt-Jakob disease DC, Gibbs CJ, Alpers M. Slow, latent and temperate virus infec- agent. Annals of neurology, 1988, 24: 466-467; Taylor DM et al. tions. Washington, DC, U.S. Government Printing Office, 1965: Preparation of growth hormone free from contamination with un- 259-262 (NINDB Monograph No. 2); Kimberlin RH, Millson GC, conventional slow viruses. Lancet, 1985, 2: 260-262; Taylor DM Hunter GD. An experimental examination of the scrapie agent in et al. Decontamination studies with the agents of bovine cell membrane mixtures. Ill. Studies of the operational size of the spongiform encephalopathy and scrapie. Archives of virology, scrapie agent. Joumal of comparative pathology, 1971, 81: 383- 1994, 139: 313-326; and Public health issues related to animal 391; Marsh RF, Hanson RP. Physical and chemical properties of and human spongiform encephalopathies: Memorandum from a the transmissible mink encephalopathy agent. Journal of virology, WHO meeting. Bulletin of the World Health Organization, 1992,70: 1969, 3: 176-180; Millson GC, Hunter GD, Kimberlin RH. The 183-190. physiochemical nature of the scrapie agent. In: Kimberlin RH, ed.

WHO Bulletin OMS. Vol 74 1996 457 Memorandum

per million per year) in adults (approximate average Accidentally transmitted CJD age, 64 years) with rapidly progressive dementia, myoclonus, ataxia, and a characteristic electro- * Progressive cerebellar syndrome in a pituitary encephalogram (EEG) with a triphasic wave pat- hormone recipient. tern. A broad spectrum of clinical features are * Sporadic CJD with a recognized exposure risk recognized, and the pattern of onset of clinical fea- (e.g. dura mater transplant). tures may vary from case to case. The duration of illness is around 5 months, on average, but cases with a prolonged clinical history have been recorded in Familial CJD many countries. The neuropathological features of CJD include spongiform change, neuronal loss and * Definite or probable CJD plus definite or prob- astrocytosis, with amyloid plaques in a minority of able CJD in a first-degree relative. cases; currently, neuropathology provides the only * Neuropsychiatric disorder plus disease-specific means of establishing diagnosis. Most cases of CJD PrP gene mutation. occur sporadically, but familial and iatrogenic cases are also recognized. Neuropathological diagnostic criteria. Definite diag- nosis of CJD and other human TSEs requires Clinical diagnostic criteria. The diagnostic criteria neuropathological confirmation on brain autopsy or, outlined below should be used. in carefully selected cases, cerebral biopsy. This is of Definite CJD is diagnosed by standard paramount importance in view of the steadily grow- neuropathological techniques and/or in reference ing spectrum of clinical and pathological pheno- laboratories by additional methodologies (prion pro- types. The many historically described variants with tein (PrP) immunocytochemistry, Western blot and/ different names have been shown to be parts of this or preparation of scrapie-associated fibrils (SAF)). spectrum. The considerable morphological variation In clinical practice, CJD is diagnosed as probable or may be influenced by the following: duration of the possible according to the following scheme: disease; prion protein (PrP) genotype; and yet un- identified factors including strains of the infectious Sporadic CJD agent. Extensive sampling from various brain areas * Probable CJD: (minimum from frontal, temporal, and occipital lobes, basal ganglia, and cerebellum) is mandatory progressive dementia; and in every autopsy of suspected spongiform enceph- typical EEG. Approximately 70% of cases of alopathy. Especially important is the comparison CJD exhibit the typical EEG pattern, which con- between cerebral and cerebellar involvement. sists of generalized triphasic periodic complexes When handling tissues and other materials from occurring at a frequency of 1 per second. There suspected cases of CJD, specific safety precautions is, however, variation in the duration of the peri- are mandatory to avoid accidental transmission and odic complexes and in the proportion of any to eliminate any infectivity.cd EEG with such indications, suggesting the need Neuropathological diagnostic criteria for CJD to establish EEG criteria for the diagnosis of and other human transmissible spongiform enceph- CJD. alopathies are summarized below. At least two of the following clinical features * CJD - sporadic, iatrogenic (recognized risk) or must be present: familial (same disease in first-degree relative): - in cerebral and/or - myoclonus; spongiform encephalopathy cerebellar cortex and/or subcortical grey matter; - visual or cerebellar disturbance (ataxia); and/or - pyramidal/extrapyramidal dysfunction; and - akinetic mutism. c Budka H et al. Tissue handling in suspected CJD and other * Possible CJD: human spongiform encephalopathies. Brain pathology, 1995, 5: 319-322. same as probable CJD but without EEG or with- dCommittee on Health Care Issues, American Neurological Association. Precaution in handling tissues, fluids, and other con- out a typical EEG and duration of illness less taminated materials from patient with documented or suspected than 2 years. CJD. Annals of neurology, 1986, 19: 75-77.

458 WHO Bulletin OMS. Vol 74 1996 Creutzfeldt-Jakob disease and transmissible spongiform encephalopathies

encephalopathy with PrP immunoreactivity Clinical and neuropathological criteria for (plaque and/or diffuse synaptic and/or patchy/ the diagnosis of the newly recognized variant perivacuolar types). form of CJD * Gerstmann-Straussler-Scheinker disease (in a A series of 12 patients has recently been identified in family with dominantly inherited progressive ataxia the United Kingdom (11 cases) and France (1 case) and/or dementia and one of a variety of PrP with a newly recognized variant form of CJD. Nine mutations): of these patients have died, all of whom were aged 41 years of age or less at death. encephalo(myelo)pathy with multicentric PrP The following clinical features are plaques. characteristic: * Familial fatal insomnia (FFI) (in member of a - a psychiatric presentation with anxiety, depres- family with PrP178 mutation): sion, withdrawal and other behavioural changes -thalamic degeneration, variable spongiform with progression to neurological abnormalities; change in cerebrum. - onset of a progressive cerebellar syndrome within weeks or months of presentation; * Kuru (in the Fore population of Papua New Guinea). While most neurological features corre- - forgetfulness and other memory impairment, spond to those of CJD with plaques, it should be with dementia in the late stages; diagnosed only in members of the Fore population of Papua New Guinea. - myoclonus or chorea in the late stages; and In the absence of PrP immunocytochemistry, - the EEG does not show the changes normally the crucial feature is the spongiform change accom- observed in classic CJD. panied by neuronal loss and gliosis. This spongiform Less common features include early onset of change is characterized by diffuse or focally clus- dysaesthesia in limbs and face at presentation, and tered small round or oval vacuoles in the neuropil extrapyramidal and pyramidal signs later in the of the deep cortical layers, cerebellar cortex or illness. subcortical grey matter, which might become con- The diagnosis of the new variant form of CJD fluent. Spongiform change should not be confused can only be made on neuropathological examina- with nonspecific spongiosis. The latter includes tion, which is mandatory for confirmation of sus- status spongiosus ("spongiform state"), comprising pected clinical cases. The neuropathological irregular cavities in gliotic neuropil following diagnostic criteria are as follows: extensive neuronal loss (including also lesions of "burnt-out" CJD), "spongy" changes in brain - abundant kuru-type amyloid plaques surrounded oedema and metabolic encephalopathies, and by vacuoles (clearly visible in H&E and PAS artefacts such as superficial cortical, perineuronal, stains); or perivascular vacuolation; focal changes indistin- - spongiform change most prominent in the basal guishable from spongiform change may occur in ganglia; some cases of Alzheimer's and diffuse Lewy body diseases. - marked thalamic astrocytosis; and Recently, immunocytochemistry for PrP has - abundant PrP deposits on immunocytochemistry, been added to classical histological techniques and including prominent "pericellular" deposition in has rapidly evolved into a most useful diagnostic tool cerebral and cerebellar cortex (especially in the (see above). However, at present it should be used molecular for diagnostic purposes only by an appropriately ex- layer). perienced laboratory. In CJD, immunoreactivity for Genetic analysis is required in every suspected PrP is manifested mainly in three patterns that fre- case to exclude familial CJD; patients should have quently overlap: plaque, diffuse synaptic and patchy/ no history of exposure to human pituitary-derived perivacuolar types. Very rarely cases might not be products or any other source of iatrogenic CJD. diagnosed by the criteria outlined above. In such The participants held that this recently de- instances confirmation must be sought by additional scribed disorder is part of the CJD spectrum; it is techniques such as PrP immunoblotting, prepara- a new variant form of CJD on the grounds of its tions for electron microscopic examination of SAF, unique clinical and pathological features. BSE has molecular biological studies, or experimental been transmitted naturally and experimentally to a transmission. range of other animal species by the oral route, and

WHO Bulletin OMS. Vol 74 1996 459 Memorandum it has been suggested that the emergent cluster of The questionnaire developed by the EU surveil- this new variant form may be a consequence of expo- lance project comprises 4 sections (A, B, F and R); sure of the human population to the BSE agent. It A and R are further divided into subsections (Al to should be emphasised that such a link has not been A10, Rl to R9). Section A of the EU questionnaire proven. (including for cases only data on clinical presenta- After a thorough review of the characteristics of tion, further investigations including EEG, neuro- natural and experimental TSEs, the Consultation pathological and genetic tests) could be used after concluded that the type of lesions and clinical pre- adaptation to the techniques usually available in the sentation of this new variant form do not provide targeted regions and countries. In section R, subsec- information on the possible origins of this disorder. tions R7 to R9 dealing with identification of risk factors by interviewing cases and controls on their Surveillance of CJD and related disorders occupation, diet and animal contacts should be sim- plified and used only within the context of special The initiation of surveillance systems should help to research projects. The person completing the ques- establish the geographical distribution of the newly tionnaire will differ in each country, but it was con- described variant of CJD, and determine the true sidered that the final WHO questionnaire should be incidence of CJD - all types and subtypes. It should applicable to any country. When reporting to WHO, also help to investigate the possible relationship of each country should specify the mechanisms of data CJD to spongiform encephalopathies in animals collection used. and to establish epidemiological parameters and risk Central registration via death certification and factors for CJD. Finally it should provide the public postal register surveillance or countrywide investiga- with accurate information, which is especially impor- tion via neurologists and neuropathologists could be tant because of the considerable public concern. used where appropriate and feasible. All centres It is accepted that with any surveillance pro- may not be able to complete all aspects of the sur- gramme, the number of cases reported will increase. veillance. If they do not have resources at the outset, There are different ways of approaching surveil- they could concentrate on identifying the newly- lance, and the methods will depend on available described variant of CJD which is likely to occur in resouces. Mechanisms of surveillance can be active younger cases. or passive and various methods are already in use in some countries. International collaboration. There is a need to plan Mechanisms for data collection. All methods of sur- international collaborative studies, including appro- veillance have advantages and disadvantages, and it priate controls to identify possible risk factors in the was agreed that for maximum comparability of data, newly described variant of CJD. Collaboration has a single method of surveillance be promoted by already started and should continue between various WHO. After obtaining permission from the Euro- institutions and the United Kingdom. Suspected pean Union (EU), and making any necessary cases might be initially checked with the CJD sur- modifications, the questionnaire-based method veillance unit in Edinburgh. elaborated by the EU for CJD surveillance should be WHO should further expand and coordinate used by WHO to develop a standard protocol for international collaboration, including surveillance, global surveillance of CJD and its variants. In a given through the Division of Emerging and other Com- country this protocol should then be used by target municable Diseases Surveillance and Control groups for the identification of suspected (possible (EMC). WHO should identify specific reference cen- The mechanisms of tres, with due regard to geographic balance, where and probable) cases. following various specific aspects of collaboration and stand- data collection should be used. ardization could be undertaken: for example, EEG * Reports with individual examination of each case interpretation, immunostaining, genetic analysis, from the specific groups involved in surveillance, e.g. tests on cerebrospinal fluid, epidemiology, transmis- neurologists, neuropathologists and health care sion experiments, etc. EMC, in collaboration with workers, especially those involved in the surveillance the Neurosciences unit of the Division of Mental of flaccid paralysis within the framework of the Health and Substance Abuse, should assist in this poliomyelitis eradication programme. by facilitating transfer of material and personnel * Specialized referral centres for screening and re- to reference centres, and assist in training as cases referred to appropriate. viewing individual by target groups. TSEs should be further investigated in other * Central registration via death certification and species, and WHO should facilitate international col- postal register surveillance. laboration in these studies with OIE, FAO, EU, and

460 WHO Bulletin OMS. Vol 74 1996 Creutzfeldt-Jakob disease and transmissible spongiform encephalopathies other international bodies dealing with veterinary transmission of the newly described variant of medicine and veterinary public health. CJD in the United Kingdom and France, as well as all other distinct human TSEs (kuru, GSS and Handling of information. Because of the great media FFI) and previously described CJD variants into interest in these diseases, and the sensitive nature of conventional in-bred strains of mice for strain- the cases, it is essential that the incoming data be typing by lesion profile/incubation time bioassay handled carefully. (some already in progress); into PrP null Initially, at least 3-monthly reports of diagnosed transgenic mice carrying multicopies of the hu- cases should be released, with any additional cases of man PrP gene to determine if this assay can dis- the newly described variant of CJD appearing in the tinguish agent strains and, if so, whether the Weekly epidemiological record. system is quicker for strain typing; and into cattle. WHO should be informed as early as possible if any such cases occur. Also, because of the media It is also recommended, even though it is of interest and economic consequences, participating a lower priority, to inoculate brain tissue from key figures in each country should be alerted so that the various human variants of spongiform en- they are able to deal accurately with media interest cephalopathies into nonhuman primates for com- and further disseminate the information within their parative purposes. own country. Although there is no evidence of infectivity (us- ing the mouse bioassay) in tissues from cattle in- Evaluation of ongoing research and definition fected with the BSE agent, other than in CNS and of future research needs distal ileum, transmission studies are recommended using tissues and derived products from BSE- The group reviewed current TSE research and infected cattle into: recommended this be continued and extended as indicated below. - transgenic PrP null mice carrying multiple copies of the bovine PrP gene; or Basic science. Because the precise nature of the causative agent and mechanism of development of - cattle (testing infectivity of products and tissues TSE is not yet known, further basic scientific re- such as milk, muscle, and gelatin); search is essential, including the following: (The purpose of these two studies is to improve the - clarification of the nature of the infective agent; sensitivity of infectivity by eliminating the species barrier) - determination of the function of PrP; - nonhuman primates (CNS tissues only by the - determination of the mechanism of pathogenic oral and intracerebral routes). PrP production; and Transmission of scrapie (from sheep and goats - pathogenesis. in the United Kingdom and other countries with and without BSE) to the following: nonhuman primates Transmission studies (by the oral and intracerebral routes) as a control There is a need to seek evidence for the natural for the above-mentioned study involving the BSE transmission of spongiform encephalopathies of agent. animals to humans; determine the distribution of Studies of the distribution of infectivity within BSE infectivity in tissues (and products derived various tissues of TSE-affected animals at different therefrom) derived from infected cattle during the times of the illness (preclinical, early and late clinical incubation period, which enter the human food or stages) by: expanding the pathogenesis studies in cat- animal feed chain; expand current studies on the tle already in progress and near completion should infectivity of human non-central nervous system any infectivity be found in cattle tissues (other than (non-CNS) tissues such as those used for transplan- the CNS and distal ileum); and considering re- tation and, in particular, blood and blood products, evaluating the distribution of tissue infectivity of despite there being no proven risk of CJD transmis- scrapie agent in sheep with newer methodologies sources. (e.g. transgenic mice). sion from these Studies to determine the tissue distribution of To this end, the following studies are infectivity in CJD and other human TSE using recommended: transgenic PrP null mice carrying multiple copies of - neuropathological and epidemiological surveil- the human PrP gene including those from whole lance of human and animal TSEs worldwide; blood, buffy coat and plasma.

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Consideration should be given to convening a mals, in order to identify genetic associations be- future WHO meeting regarding the infectivity of tween distantly related species (in progress). human non-CNS tissues of CJD patients such as those used for transplantation, in particular blood Treatment methods. There is an urgent need to de- and blood products. It is noted that the pathogenesis velop a strategy for the prevention and treatment of of CJD may differ with the route of exposure and human TSE based on genetic, biological and chemi- strain of agent. cal approaches which can be further developed as a result of findings from basic science research. It was Diagnostic studies. A recent investigation on CSF noted, however, that some preventive strategies for marker proteins appears to provide the potential for some animal TSE are already in place. a sensitive in-vivo test for CJD and related disorders. However, further studies on cases of CJD, other neu- Use of in-vitro tests and animals for research. Every rological disorders and control cases are required to effort should be made to develop in-vitro tests for establish the diagnostic value of this test in human diagnosis and research, and studies requiring the use and animal TSEs. of laboratory and other animals should involve the The participants made the recommendations smallest number of animals possible. shown below. * Rapid, reliable tests with high sensitivity and Participants specificity, particularly in the early or pre-clinical stages of illness, from easily obtained sources (e.g. WHO Consultation on public health body fluids) are urgently needed to diagnose both issues related to human and animal human and animal TSEs. transmissible spongiform * Further validation studies of currently available encephalopathies, Geneva, 2-3 April 1996 diagnostic tests as well as of those being developed, should be initiated. Dr A. Alperovitch, Paris, France; Dr R. Bradley, Addlestone, Surrey, England; Professor Dr H. Diringer, Biosafety studies. Further studies should be per- Berlin, Germany; Dr J. Gibbs (Co-Chairman), Bethesda, formed on current physicochemical protocols, alone MD, USA; Dr F. Horaud, Paris, France; Dr J.W. Ironside, and in various combinations, as well as to develop Edinburgh, Scotland; Dr H. Longbottom (Rapporteur), new protocols that completely inactivate infectivity Canberra, Australia; Dr J. Losos (Chairman), Ottawa, from: Canada; Professor J.R. Pattison, London, England; Dr L. Schonberger, Atlanta, GA, USA; Professor P. Smith, - contaminated surgical instruments, equipment London, England; Professor A. Somogyi, Berlin, Germany; and accommodation; and and Professor M. Vandevelde, Innerberg, Switzerland. FAO: Dr Y. Cheneau and Dr P. Roeder. Intema- - animal products and animal waste by using Office the most sensitive methods now available (e.g. tional des Epizooties: Dr R. Reichard. European Commis- transgenic mice). sion: Dr A.J. Wilson and Professor P. Peters. Observers: Professor H. Budka (Austria); Dr T. Baron and Dr 1. Capek Research should be considered to examine any (France); Dr E. Weavers, Ms B. Cannon, Mr D. Denham, risks that may arise during conventional slaughter and Dr J. Devlin (Ireland); Dr M. d'Alessandro (Italy); Dr Y. of TSE-infected but clinically healthy animals in Kaji, Dr T. Kurata, and Dr E. Sanatani (Japan); Mr C. Feek abattoirs. (New Zealand); Dr L. Malychev (Russian Federation); Dr The complete pathway of all tissues from food B. Hornlimann (Switzerland); Dr A. Wight, and Dr L. animals should be audited to determine their fate, Robinson (United Kingdom); Dr B.W.J. Mahy, Dr T. whether for food, feed, medicinal/biological prod- Gomez, Dr K. Bernard, and Dr Clara Witt (USA): WHO ucts or devices, or other uses. Secretariat: Dr H. Nakajima, Dr Hu Ching-Li, Dr D.L. Heymann, Dr F.-X. Meslin (Secretary), Dr L.J. Martinez, Genetic studies. The studies outlined below should Dr K. Stohr, Dr G.A. Clugston, Dr E. Griffiths, Dr F. be carried out. Kaferstein, Dr S, Miyagawa, Dr C. Bolis, Dr A. Janca, Dr J. * Extend the molecular genetic studies of the PrP Orley, Dr M. Kaplan, Dr J.-C. Alary, Dr 0. Cosivi, Dr J. gene (and other genes possibly associated with TSE) LeDuc, Dr M.C. Thuriaux, and Dr E. Tikhomirov. WHO in humans and and Regional Office for the Americas: Dr S. Corber. WHO animals, especially cattle sheep. Regional Office for the Eastem Mediterranean: Dr M.H. * Study the extent of polymorphisms in the PrP Wahdan. WHO Regional Office for Europe: Dr G. Klein gene of natural populations of human and other ani- and Dr C.A. Van der Heyden.

462 WHO Bulletin OMS. Vol 74 1996 Creutzfeldt-Jakob disease and transmissible spongiform encephalopathies

WHO Consultation on clinical and Oxford, England; Dr C. Masters, Victoria, Australia; Pro- neuropathological characteristics of the fessor I.P. Ndiaye Dakar, Senegal; Dr A.L. Taratuto new variant of CJD and (Co-Chairman), Buenos Aires, Argentina; Professor C. other animal Weismann (Co-Chairman), Zurich, Switzerland; Dr R. Will, transmissible spongiform Edinburgh, Scotland; Dr G.A. Wells, Addlestone, Surrey, encephalopathies, Geneva, 14-16 May England. Observers: Mr. P. Jones (England), Dr T.C. 1996 Jones (USA), Dr Y. Kaji (Japan), Dr M.M. Kaplan (Switzerland); Dr H. Kretzschmar (Germany); Mrs E. Dr M. Ben Hamida, Tunis, Tunisia; Dr R. Bradley, Laurence (England); Dr K. Miura (Japan); Dr D.R.O. Addlestone, Surrey, England; Dr H. Budka, Vienna, Aus- Morrison (Switzerland); Dr M. Pagel (England); Dr M.N. tria; Dr L. Cartier, Santiago de Chile, Chile; Dr D.K. Dastur, Ricketts (Canada); Dr L.B. Schonberger (USA); Dr C.J. Bombay, India; Dr J. Gibbs (Chairman), Bethesda, MD, Van Gelderen (Argentina). WHO Secretariat: Dr H. USA; Dr Y.P. Guo, Beijing, China; Dr W.J. Hadlow, Ham- Nakajima, Dr Hu Ching-Li, Dr C.L. Bolis (Co-Secretary), Dr ilton, MT, USA; Dr T. Hemachudha, Bangkok, Thailand; Dr J. Emmanuel, Dr E. Griffiths, Dr D.L. Heymann, Dr A. J.W. Ironside (Co-Rapporteur), Edinburgh, Scotland; Dr Janca, Dr F.-X. Meslin (Secretary), Dr S. Miyagawa, Dr K. Kenney (Co-Rapporteur), Bethesda, MD, USA; Dr S.A. Orzeszyna, Dr L.L. Prilipko, Dr G. Rodier, Dr K. C. Keohane (Co-Rapporteur), Wilton, Cork, Ireland; Pro- Stohr, Dr M. Thuriaux, Dr C. Dora, Dr S. Plianbangchang, fessor T. Kitamoto, Sendai, Japan; Dr D.C. Krakauer, Dr K. Morita.

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