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.

MemorandaIMemorandums 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 At a WHO Consultation held in Geneva on 2-3 April 1996 a group of international experts reviewed the public health issues related to bovine spongiform encephalopathy (BSE) and issued recommendations on various cattle products and by-products in order to protect the health of consumers. As a follow-up, a second Consultation was held in Geneva on 14-16 May 1996 to examine the clinical, neurological, and neuropathological findings associated with a new * This Memorandum is based on the reports of two WHO Consul- tations: Report of a WHO Consultation on public health issues related to human and animal transmissible spongiform encephalopathies, Geneva, 2-3 April 1996 (unpublished docu- ment WHO/EMC/DIS/96.147); and Report of the WHO Consulta- tion on clinical and neuropathological characteristics of the new vartiant of CJD and other human and animal transmissible spongiform encephalopathies, Geneva, 14-16 May 1996 (unpub- 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, Disease Surveillance and Control, Division of Emerging and other Communicable Diseases Surveillance and Control, World Health Organization, 1211 Geneva 27, Switzerland. A French translation of this article will appear in a later edition of the Bulletin. Reprint No. 5726 variant of Creutzfeldt-Jakob disease (CJD); to com- pare these findings with those of other transmissible spongiform encephalopathies (TSEs)a and examine the putative relationship between human TSE and animal spongiform encephalopathies; to propose a protocol for the diagnosis and surveillance of CJD and related diseases; and to review the tests devel- oped for early diagnosis of TSEs and make recom- mendations for further research. Bovine spongiform encephalopathy Background BSE is a transmissible spongiform encephalopathy that was first identified in the United Kingdom in 1986. Transmission of BSE to cattle appears to have a TSE is a term for a group of diseases associated with a transmis- sible agent, the nature of which is not fully known. The agent displays many virus-like features, such as strain variation and mutation, but differs from conventional viruses in being exception- ally resistant to heat, ultraviolet and ionizing radiation, and to 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- centrate feed (sheep or cattle may have been the original source of the agent). The epidemic in the United Kingdom (the only country with a high inci- dence of BSE) appears to have been due mainly to the recycling of affected bovine material to cattle before the July 1988 ruminant feed ban became effective. The epidemic of BSE in the United Kingdom is progressively declining in response to the control 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 succumbed to spongiform encephalopathies (SEs) via the same feed source as cattle. Domestic cats (71), puma (3), ocelot (2), and cheetah (4) have de- veloped feline SE; the wild cats were probably in- fected after consuming BSE-infected tissues from the central nervous system (CNS) of cattle. Unsuc- cessful attempts have been made to transmit BSE to hamsters and chickens but it has been transmitted to cattle, sheep, goats, pigs, marmosets, mink and mice by parenteral challenge. Experimental oral transmission has been at- tempted in all these species except marmosets and has been successful in all except pigs, with longer incubation periods than following parenteral chal- lenge, despite much larger doses being used. Pigs remain healthy nearly 6 years' post-challenge and tissues from a 2-year interim kill (which did not show clinical or pathological evidence of SE) did not trans- mit BSE to mice. The BSE agent is different from any known strains of historical or contemporary scrapie and retains its biological characteristics fol- lowing natural or experimental passage through six species, despite their different PrP gene sequences. The BSE agent from nine different cattle sources is biologically identical. The only tissues from clinically affected confirmed cases of BSE that have shown infectivity are the brain, retina, cervical and terminal spinal cord, and in experimentally orally challenged cattle during incubation, the distal ileum, which is consistently infected from 6-18 months' post- challenge inclusive. No infectivity has been found in muscle (meat), milk, mammary gland, placenta, bone marrow or peripheral nerve from clinical cases and over 40 other tissues. Nine studies (6 experimental and 3 epidemio- logical) have examined the possibilities for maternal transmission. The conclusions of these studies are that maternal transmission cannot be excluded but if it is occurring it is at a low and undetectable incidence. No closed herd study has been under- taken to clarify these aspects, but a cohort study is under way and will be completed early in 1997. A study in cattle has revealed that 1 g of BSE- infected cow brain is sufficient to cause BSE in a cow by the oral route. A comparative bioassay in cattle and mice provisionally shows the titre measured in mice is 100-1000 times lower than that measured in cattle. Spleen and lymph node pools administered intracerebrally (i.c.) have not transmitted BSE to mice, and cows inoculated with such pools remain alive for twice the incubation period of those inocu- lated with a 1/10 dilution of brain tissue. Neuropathological aspects of the new variant of CJD A new variant form of CJD, with a characteristic clinical and pathological phenotype, has been identi- fied in the United Kingdom in a series of 11 young patients. The characteristic neuropathological fea- tures are the presence of large numbers of kuru-type PrP-positive amyloid plaques surrounded by a halo of spongiform change in the cerebral cortex (particu- larly the occipital lobe), thalamic gliosis, and exten- sive deposition of PrP in all grey matter regions, particularly the cerebellum (including the molecular layer); spongiform changes are most evident in the basal ganglia. These cases share an early age at onset of symptoms, an unusual clinical course, with early psychiatric features and a prolonged duration of ill- ness, all characteristics which had not been previ- ously reported in the United Kingdom. One similar case has recently been confirmed in France. Com- parison of these cases with over 200 CJD cases in the United Kingdom Surveillance Project, which covers also historical CJD cases, and with cases in other European Surveillance Projects, has failed to iden- tify any similar cases. Immunocytochemical detection of prion protein in CJD A total of 179 cases of sporadic CJD have been confirmed by immunocytochemical detection of prion protein (PrP) with both monoclonal and polyclonal antibodies on paraffin sections of various brain regions pretreated by hydrated autoclaving. PrP deposition patterns included fine granular labeling of synaptic type (in about 90% of cere- bral and cerebellar cortical specimens), patchy/ perivacuolar deposits (mostly (38%) in cerebrum), and plaque deposits (mostly (25%) in cerebellum). Types of deposition and amount of immunoreac- tive PrP varied between cases but remained rela- tively constant between different regions of an WHO Bulletin OMS. Vol 74 1996454 Creutzfeldt-Jakob disease and transmissible spongiform encephalopathies individual brain. The brain stem was only involved infrequently (21% with PrP deposits). PrP immu- nocytochemistry is a very reliable diagnostic tool and detects a limited range of characteristic types of PrP deposition that is relatively uniformly distributed in an individual brain. Presence of Alzheimer-type brain amyloid may modify PrP deposition. Phylogenetic analysis of prion disease A study of the prion protein is being undertaken to identify major trends in its evolution by means of a comparative analysis of healthy prion genes. Genetic differences among species, as well as genetic polymorphisms within species, may prove valuable in understanding the nature of the species barrier, and the more likely routes of transmission of the TSEs. CSF protein marker detection test A simple, rapid cerebrospinal fluid (CSF) test has recently been developed that should prove a useful aid in confirming the clinical diagnosis of a spongiform encephalopathy, human or animal. The 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 test's reliability in BSE-affected cattle and patients with the newly recognized variant form of CJD and to clarify the association of proteins with these diseases. National reports on CJD and other related disorders Eastern Mediterranean Tunisia. CJD is rare and sporadic in Tunisia if we exclude the high incidence of CJD reported in Israel among Jewish immigrants of Tunisian origin. Since 1980 a total of 11 cases have been reported, but in view of the difficulty in diagnosing the condition the true incidence is probably higher. Surveillance of CJD and a CJD registry should be established, and collaboration with veterinary authorities should be set up to study the epidemiology of scrapie and the possible relationship between CJD and animal spongiform encephalopathies in the country. Europe Austria. Between 1969 and 1995, a total of 80 cases of CJD were confirmed. The annual incidence has increased in recent years (1969-85: 0.18 per million; 1986-94: 0.67 per million; 1995: 1.25 per million), probably reflecting improved awareness about the condition and better diagnosis rather than a real increase in incidence. No cases of BSE have been reported in Austria. Germany. Systematic surveillance of CJD has been carried out since June 1993, and based on the criteria of the European Union CJD Surveillance Group, 63 probable and definite cases were recorded in 1994 (incidence, 0.77 per million), and 64 cases in 1995 (0.78 per million). The clinical and patho- logical features of the new variant form of CJD have not been observed in Germany. A study of more than 150 cases of CJD and the same number of con- trols has not indicated occupational or other risk factors. Ireland. Based on death-certificate data, there have been 17 deaths from CJD since 1980, two involving individuals aged under 48 years. Since 1989, there have been 126 cases of BSE (annual incidence, 17 cases), approximately a third involving animals im- ported from the United Kingdom. Latin America Argentina. Over the period 1980-96, a total of 30 patients with CJD were confirmed neuro- pathologically. No cases of Gerstmann-Straussler- Scheinker (GSS) disease or of fatal familial insomnia (FFI) have been reported. There is no official sur- veillance of CJD, although there is surveillance of BSE and scrapie. No case of BSE has been reported. Brazil. In each region of the country 1-2 cases of CJD have been reported over the last 5 years. No increase has occurred in the number of cases of clas- sical CJD and there have been no cases of the new variant form of CJD. There is no surveillance of CJD. Chile. Over the period 1964-86, a total of 69 cases of CJD were reported (38 females, 31 males): 78.3% were sporadic and the mean age at death was 55.4 years (range, 23-75 years). Over the last 10 years, 22 neuropathologically confirmed and 25 probable cases have been reported. WHO Bulletin OMS. Vol 74 1996 455 Memorandum Mexico. Biopsies are not carried out on most of the probable or possible case of CJD and no docu- mented cases of GSS or FFI have been reported. Despite surveillance for BSE and scrapie no cases have been reported. Uruguay. Some cases of sporadic CJD and of GSS have been reported. No surveillance of CJD is car- ried out but there is no evidence for an increase in its incidence, and no atypical cases have been reported. Venezuela. No surveillance of CJD is carried out, but possible and probable cases have been reported; there have been no atypical cases. Cases of GSS have not been reported. South-east Asia India. A total of 30 cases of CJD were reported in India in 1990, with no cases of V-CJD. Approxi- mately 15 cases have occurred in the Bombay area over the last 20-25 years, and of the six that were autopsied two were vegetarians. Also, one case ex- hibited characteristics typical of GSS. There is no definite evidence that scrapie occurs in Western India. Sub-Saharan Africa 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- gical interventions (including dura-mater grafts); use 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 the low recorded incidence of CJD and other similar conditions may be explained, inter alia, by the fol- lowing: the absence of surveillance and control; the low level of use by the general population of quali- fied medical practitioners; the small number of neurospecialists; and the underrepresentation of at- risk age groups in the general population, with over- 60-year-olds comprising only 3% of the total. No cases of scrapie or of BSE have been re- corded in Senegal. Western Pacific Australia and New Zealand. The annual incidence of CJD is approximately 1 case per million, with a de- mographic profile similar to that in Europe and North America. An atypical cluster of cases related to exposure to gonadotrophin of human pituitary origin has, however, been reported. To date there have been no cases that fulfil all the criteria for the new variant form of CJD, but cases that meet some of them have occurred. The absence of BSE and scrapie in Australia and New Zealand makes the epidemiological surveillance of CJD in these coun- tries an important source of information for assess- ing the zoonotic risk of these diseases. Japan. Since 1979 analysis of the incidence of CJD has been carried out based on death certificate infor- mation. Over the period 1987 to 1990 a total of 216 cases of CJD occurred among those aged 15 years and older. To date there have been no cases of the new variant form of CJD in Japan. A na- tional surveillance project on CJD and related dis- eases, covering 3400 hospitals with neurological/ psychiatric facilities, was established in 1996; the results will be reported by March 1997. Although no cases of BSE have been reported in Japan, a surveillance system for BSE as well as scrapie was set up in March 1996. Thailand. There are no official statistics on the inci- dence of CJD in Thailand, but it is estimated that there have been no more than 25 cases over the last 20 years, all similar to the classic sporadic pattern in terms of age of onset, clinical presentations, EEG changes and duration of illness. Conclusions and recommendations Recommendations for public health During the Consultation held on 2-3 April, the recommendations shown below were made for the protection of public health. * No part or product of any animal that has shown signs of a TSE should enter any food chain (human or animal). In particular, the following should be noted: - all countries must ensure the killing and safe dis- posal of all parts or products of such animals so that TSE infectivity cannot enter any food chain; and - all countries should review their rendering proce- dures to ensure that they effectively inactivate TSE agents. * All countries should establish continuous surveil- lance and compulsory notification for BSE based WHO Bulletin OMS. Vol 74 1996456 Creutzfeldt-Jakob disease and transmissible spongiform encephalopathies on the recommendations of the International Ani- mal Health Code of the Office International des Epizooties (OIE). In the absence of surveillance data the status of a country with respect to the occurrence of BSE must be considered as unknown. * Countries should not permit tissues that are likely to contain the BSE agent to enter any food chain (human or animal). * All countries should ban the use of ruminant tis- sues in ruminant feed. * With respect to specific products, the following apply: milk and milk products, even in countries with a high incidence of BSE, are considered safe. There is evidence from other animal and human spongiform encephalopathies to suggest that milk does not transmit these diseases; gelatin in the food chain is considered to be safe if produced by a manufacturing process utilizing production conditions that significantly inacti- vate any residual infectivity that may have been present in source tissues; and tallow is similarly considered safe if effective ren- 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- sidered lower than that in the latter country. Expo- sure to the BSE agent in the United Kingdom was likely to be higher prior to introduction of the cur- rent BSE regulations. b Selected references: Brown P, Rohwer RG, Gajdusek DC. Newer data on the inactivation of scrapie virus or Creutzfeldt- Jakob disease virus in brain tissue. Journal of infectious diseases, 1986, 153: 1145-1148; Di Martino A et al. Purification of non- infectious ganglioside preparations from scrapie-infected brain tis- sue. Archives of virology, 1992, 124: 111-121; Diringer H, Kimberlin RH. Infectious scrapie agent is not as small as recent claims suggest. Bioscience reports, 1983, 3: 563-568; Hunter GD, Millson GC. Studies on the heat stability and chromato- graphic behaviour of the scrapie agent. Joumal of general micro- biology, 1964, 37: 251-258; Hunter GD. Progress toward the isolation and characterization of the scrapie agent. In: Gajdusek DC, Gibbs CJ, Alpers M. Slow, latent and temperate virus infec- tions. Washington, DC, U.S. Government Printing Office, 1965: 259-262 (NINDB Monograph No. 2); Kimberlin RH, Millson GC, Hunter GD. An experimental examination of the scrapie agent in cell membrane mixtures. Ill. Studies of the operational size of the scrapie agent. Joumal of comparative pathology, 1971, 81: 383- 391; Marsh RF, Hanson RP. Physical and chemical properties of the transmissible mink encephalopathy agent. Journal of virology, 1969, 3: 176-180; Millson GC, Hunter GD, Kimberlin RH. The physiochemical nature of the scrapie agent. In: Kimberlin RH, ed. The risks at present associated with exposure to the BSE agent from beef and beef products will be minimized if the recommendations of the present consultation are implemented. * Risks from medicinal products and medical de- vices containing bovine tissues are as follows: - the importance is reiterated of obtaining bovine materials destined for the pharmaceutical indus- try only from countries that have a surveillance system in place and which report either no or only sporadic cases of BSE; - removal and inactivation procedures contribute to the reduction of the risk of infection but it must be recognized that the BSE agent is remark- ably resistant to physico-chemical procedures that destroy the infectivity of common microor- ganisms; - measures recommended to national health au- thorities to minimize the risk of transmitting the agent causing BSE via medicinal products, in par- ticular parenteral products, that were developed at a previous WHO Consultation in 1991 con- tinue to be generally applicable;b and - it is recommended that these measures be re- viewed and, if necessary, strengthened as more information becomes available. Clinical and neuropathological criteria for the diagnosis of clinical CJD and other human TSEs CJD classically occurs as a rare disorder with worldwide distribution (approximate incidence: 1 Slow virus diseases of animals and man. Amsterdam, North- Holland, 1976: 243-266; Pocchiari M et al. Can potential hazard of Creutzfeldt-Jakob disease infectivity be reduced in the produc- tion of human growth hormone? Inactivation experiments with the 263K strain of scrapie. Archives of virology, 1988, 98: 131-135; Pocchiari M et al. Combination ultrafiltration and 6M urea treat- ment of human growth hormone effectively minimizes risk from potential Creutzfeldt-Jakob disease virus contamination. Hormone research, 1991, 35: 161-166; Taguchi F et al. Proposal for a procedure for complete inactivation of the Creutzfeldt-Jakob dis- ease agent. Archives of virology, 1991, 119: 297-301; Tamai Y, Taguchi F, Miura S. Inactivation of the Creutzfeldt-Jakob disease agent. Annals of neurology, 1988, 24: 466-467; Taylor DM et al. Preparation of growth hormone free from contamination with un- conventional slow viruses. Lancet, 1985, 2: 260-262; Taylor DM et al. Decontamination studies with the agents of bovine spongiform encephalopathy and scrapie. Archives of virology, 1994, 139: 313-326; and Public health issues related to animal and human spongiform encephalopathies: Memorandum from a WHO meeting. Bulletin of the World Health Organization, 1992,70: 183-190. WHO Bulletin OMS. Vol 74 1996 457 Memorandum per million per year) in adults (approximate average age, 64 years) with rapidly progressive dementia, myoclonus, ataxia, and a characteristic electro- encephalogram (EEG) with a triphasic wave pat- tern. A broad spectrum of clinical features are recognized, and the pattern of onset of clinical fea- 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 many countries. The neuropathological features of CJD include spongiform change, neuronal loss and astrocytosis, with amyloid plaques in a minority of cases; currently, neuropathology provides the only means of establishing diagnosis. Most cases of CJD occur sporadically, but familial and iatrogenic cases are also recognized. Clinical diagnostic criteria. The diagnostic criteria outlined below should be used. Definite CJD is diagnosed by standard neuropathological techniques and/or in reference laboratories by additional methodologies (prion pro- tein (PrP) immunocytochemistry, Western blot and/ or preparation of scrapie-associated fibrils (SAF)). In clinical practice, CJD is diagnosed as probable or possible according to the following scheme: Sporadic CJD * Probable CJD: progressive dementia; and typical EEG. Approximately 70% of cases of CJD exhibit the typical EEG pattern, which con- sists of generalized triphasic periodic complexes occurring at a frequency of 1 per second. There is, however, variation in the duration of the peri- odic complexes and in the proportion of any EEG with such indications, suggesting the need to establish EEG criteria for the diagnosis of CJD. At least two of the following clinical features must be present: - myoclonus; - visual or cerebellar disturbance (ataxia); - pyramidal/extrapyramidal dysfunction; and - akinetic mutism. * Possible CJD: same as probable CJD but without EEG or with- out a typical EEG and duration of illness less than 2 years. Accidentally transmitted CJD * Progressive cerebellar syndrome in a pituitary hormone recipient. * Sporadic CJD with a recognized exposure risk (e.g. dura mater transplant). Familial CJD * Definite or probable CJD plus definite or prob- able CJD in a first-degree relative. * Neuropsychiatric disorder plus disease-specific PrP gene mutation. Neuropathological diagnostic criteria. Definite diag- nosis of CJD and other human TSEs requires neuropathological confirmation on brain autopsy or, in carefully selected cases, cerebral biopsy. This is of paramount importance in view of the steadily grow- ing spectrum of clinical and pathological pheno- types. The many historically described variants with different names have been shown to be parts of this spectrum. The considerable morphological variation may be influenced by the following: duration of the disease; prion protein (PrP) genotype; and yet un- identified factors including strains of the infectious agent. Extensive sampling from various brain areas (minimum from frontal, temporal, and occipital lobes, basal ganglia, and cerebellum) is mandatory in every autopsy of suspected spongiform enceph- alopathy. Especially important is the comparison between cerebral and cerebellar involvement. When handling tissues and other materials from suspected cases of CJD, specific safety precautions are mandatory to avoid accidental transmission and to eliminate any infectivity.cd Neuropathological diagnostic criteria for CJD and other human transmissible spongiform enceph- alopathies are summarized below. * CJD - sporadic, iatrogenic (recognized risk) or familial (same disease in first-degree relative): - spongiform encephalopathy in cerebral and/or cerebellar cortex and/or subcortical grey matter; and/or c Budka H et al. Tissue handling in suspected CJD and other human spongiform encephalopathies. Brain pathology, 1995, 5: 319-322. dCommittee on Health Care Issues, American Neurological Association. Precaution in handling tissues, fluids, and other con- taminated materials from patient with documented or suspected 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 (plaque and/or diffuse synaptic and/or patchy/ perivacuolar types). * Gerstmann-Straussler-Scheinker disease (in a family with dominantly inherited progressive ataxia and/or dementia and one of a variety of PrP mutations): encephalo(myelo)pathy with multicentric PrP plaques. * Familial fatal insomnia (FFI) (in member of a family with PrP178 mutation): -thalamic degeneration, variable spongiform change in cerebrum. * Kuru (in the Fore population of Papua New Guinea). While most neurological features corre- spond to those of CJD with plaques, it should be diagnosed only in members of the Fore population of Papua New Guinea. In the absence of PrP immunocytochemistry, the crucial feature is the spongiform change accom- panied by neuronal loss and gliosis. This spongiform change is characterized by diffuse or focally clus- tered small round or oval vacuoles in the neuropil of the deep cortical layers, cerebellar cortex or subcortical grey matter, which might become con- fluent. Spongiform change should not be confused with nonspecific spongiosis. The latter includes status spongiosus ("spongiform state"), comprising irregular cavities in gliotic neuropil following extensive neuronal loss (including also lesions of "burnt-out" CJD), "spongy" changes in brain oedema and metabolic encephalopathies, and artefacts such as superficial cortical, perineuronal, or perivascular vacuolation; focal changes indistin- guishable from spongiform change may occur in some cases of Alzheimer's and diffuse Lewy body diseases. Recently, immunocytochemistry for PrP has been added to classical histological techniques and has rapidly evolved into a most useful diagnostic tool (see above). However, at present it should be used for diagnostic purposes only by an appropriately ex- perienced laboratory. In CJD, immunoreactivity for PrP is manifested mainly in three patterns that fre- quently overlap: plaque, diffuse synaptic and patchy/ perivacuolar types. Very rarely cases might not be diagnosed by the criteria outlined above. In such instances confirmation must be sought by additional techniques such as PrP immunoblotting, prepara- tions for electron microscopic examination of SAF, molecular biological studies, or experimental transmission. Clinical and neuropathological criteria for the diagnosis of the newly recognized variant form of CJD A series of 12 patients has recently been identified in the United Kingdom (11 cases) and France (1 case) with a newly recognized variant form of CJD. Nine of these patients have died, all ofwhom were aged 41 years of age or less at death. The following clinical features are characteristic: - a psychiatric presentation with anxiety, depres- sion, withdrawal and other behavioural changes with progression to neurological abnormalities; - onset of a progressive cerebellar syndrome within weeks or months of presentation; - forgetfulness and other memory impairment, with dementia in the late stages; - myoclonus or chorea in the late stages; and - the EEG does not show the changes normally observed in classic CJD. Less common features include early onset of dysaesthesia in limbs and face at presentation, and extrapyramidal and pyramidal signs later in the illness. The diagnosis of the new variant form of CJD can only be made on neuropathological examina- tion, which is mandatory for confirmation of sus- pected clinical cases. The neuropathological diagnostic criteria are as follows: - abundant kuru-type amyloid plaques surrounded by vacuoles (clearly visible in H&E and PAS stains); - spongiform change most prominent in the basal ganglia; - marked thalamic astrocytosis; and - abundant PrP deposits on immunocytochemistry, including prominent "pericellular" deposition in cerebral and cerebellar cortex (especially in the molecular layer). Genetic analysis is required in every suspected case to exclude familial CJD; patients should have no history of exposure to human pituitary-derived products or any other source of iatrogenic CJD. The participants held that this recently de- scribed disorder is part of the CJD spectrum; it is a new variant form of CJD on the grounds of its unique clinical and pathological features. BSE has been transmitted naturally and experimentally to a 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 this new variant form may be a consequence of expo- sure of the human population to the BSE agent. It should be emphasised that such a link has not been proven. After a thorough review of the characteristics of natural and experimental TSEs, the Consultation concluded that the type of lesions and clinical pre- sentation of this new variant form do not provide information on the possible origins of this disorder. Surveillance of CJD and related disorders The initiation of surveillance systems should help to establish the geographical distribution of the newly described variant of CJD, and determine the true incidence of CJD- all types and subtypes. It should also help to investigate the possible relationship of CJD to spongiform encephalopathies in animals and to establish epidemiological parameters and risk factors for CJD. Finally it should provide the public with accurate information, which is especially impor- tant because of the considerable public concern. It is accepted that with any surveillance pro- gramme, the number of cases reported will increase. There are different ways of approaching surveil- lance, and the methods will depend on available resouces. Mechanisms of surveillance can be active or passive and various methods are already in use in some countries. Mechanisms for data collection. All methods of sur- veillance have advantages and disadvantages, and it was agreed that for maximum comparability of data, a single method of surveillance be promoted by WHO. After obtaining permission from the Euro- pean Union (EU), and making any necessary modifications, the questionnaire-based method elaborated by the EU for CJD surveillance should be used by WHO to develop a standard protocol for global surveillance of CJD and its variants. In a given country this protocol should then be used by target groups for the identification of suspected (possible and probable) cases. The following mechanisms of data collection should be used. * Reports with individual examination of each case from the specific groups involved in surveillance, e.g. neurologists, neuropathologists and health care workers, especially those involved in the surveillance of flaccid paralysis within the framework of the poliomyelitis eradication programme. * Specialized referral centres for screening and re- viewing individual cases referred to by target groups. * Central registration via death certification and postal register surveillance. The questionnaire developed by the EU surveil- lance project comprises 4 sections (A, B, F and R); A and R are further divided into subsections (Al to A10, Rl to R9). Section A of the EU questionnaire (including for cases only data on clinical presenta- tion, further investigations including EEG, neuro- pathological and genetic tests) could be used after adaptation to the techniques usually available in the targeted regions and countries. In section R, subsec- tions R7 to R9 dealing with identification of risk factors by interviewing cases and controls on their occupation, diet and animal contacts should be sim- plified and used only within the context of special research projects. The person completing the ques- tionnaire will differ in each country, but it was con- sidered that the final WHO questionnaire should be applicable to any country. When reporting to WHO, each country should specify the mechanisms of data collection used. Central registration via death certification and postal register surveillance or countrywide investiga- tion via neurologists and neuropathologists could be used where appropriate and feasible. All centres may not be able to complete all aspects of the sur- veillance. If they do not have resources at the outset, they could concentrate on identifying the newly- described variant of CJD which is likely to occur in younger cases. International collaboration. There is a need to plan international collaborative studies, including appro- priate controls to identify possible risk factors in the newly described variant of CJD. Collaboration has already started and should continue between various institutions and the United Kingdom. Suspected cases might be initially checked with the CJD sur- veillance unit in Edinburgh. WHO should further expand and coordinate international collaboration, including surveillance, through the Division of Emerging and other Com- municable Diseases Surveillance and Control (EMC). WHO should identify specific reference cen- tres, with due regard to geographic balance, where various specific aspects of collaboration and stand- ardization could be undertaken: for example, EEG interpretation, immunostaining, genetic analysis, tests on cerebrospinal fluid, epidemiology, transmis- sion experiments, etc. EMC, in collaboration with the Neurosciences unit of the Division of Mental Health and Substance Abuse, should assist in this by facilitating transfer of material and personnel to reference centres, and assist in training as appropriate. TSEs should be further investigated in other species, andWHO should facilitate international col- laboration in these studies with OIE, FAO, EU, and WHO Bulletin OMS. Vol 74 1996460 Creutzfeldt-Jakob disease and transmissible spongiform encephalopathies other international bodies dealing with veterinary medicine and veterinary public health. Handling of information. Because of the great media interest in these diseases, and the sensitive nature of the cases, it is essential that the incoming data be handled carefully. Initially, at least 3-monthly reports of diagnosed cases should be released, with any additional cases of the newly described variant of CJD appearing in the Weekly epidemiological record. WHO should be informed as early as possible if any such cases occur. Also, because of the media interest and economic consequences, participating key figures in each country should be alerted so that they are able to deal accurately with media interest and further disseminate the information within their own country. Evaluation of ongoing research and definition of future research needs The group reviewed current TSE research and recommended this be continued and extended as indicated below. Basic science. Because the precise nature of the causative agent and mechanism of development of TSE is not yet known, further basic scientific re- search is essential, including the following: - clarification of the nature of the infective agent; - determination of the function of PrP; - determination of the mechanism of pathogenic PrP production; and - pathogenesis. Transmission studies There is a need to seek evidence for the natural transmission of spongiform encephalopathies of animals to humans; determine the distribution of BSE infectivity in tissues (and products derived therefrom) derived from infected cattle during the incubation period, which enter the human food or animal feed chain; expand current studies on the infectivity of human non-central nervous system (non-CNS) tissues such as those used for transplan- tation and, in particular, blood and blood products, despite there being no proven risk of CJD transmis- sion from these sources. To this end, the following studies are recommended: - neuropathological and epidemiological surveil- lance of human and animal TSEs worldwide; transmission of the newly described variant of CJD in the United Kingdom and France, as well as all other distinct human TSEs (kuru, GSS and FFI) and previously described CJD variants into conventional in-bred strains of mice for strain- typing by lesion profile/incubation time bioassay (some already in progress); into PrP null transgenic mice carrying multicopies of the hu- man PrP gene to determine if this assay can dis- tinguish agent strains and, if so, whether the system is quicker for strain typing; and into cattle. It is also recommended, even though it is of a lower priority, to inoculate brain tissue from the various human variants of spongiform en- cephalopathies into nonhuman primates for com- parative purposes. Although there is no evidence of infectivity (us- ing the mouse bioassay) in tissues from cattle in- fected with the BSE agent, other than in CNS and distal ileum, transmission studies are recommended using tissues and derived products from BSE- infected cattle into: - transgenic PrP null mice carrying multiple copies of the bovine PrP gene; or - cattle (testing infectivity of products and tissues such as milk, muscle, and gelatin); (The purpose of these two studies is to improve the sensitivity of infectivity by eliminating the species barrier) - nonhuman primates (CNS tissues only by the oral and intracerebral routes). Transmission of scrapie (from sheep and goats in the United Kingdom and other countries with and without BSE) to the following: nonhuman primates (by the oral and intracerebral routes) as a control for the above-mentioned study involving the BSE agent. Studies of the distribution of infectivity within various tissues of TSE-affected animals at different times of the illness (preclinical, early and late clinical stages) by: expanding the pathogenesis studies in cat- tle already in progress and near completion should any infectivity be found in cattle tissues (other than the CNS and distal ileum); and considering re- evaluating the distribution of tissue infectivity of scrapie agent in sheep with newer methodologies (e.g. transgenic mice). Studies to determine the tissue distribution of infectivity in CJD and other human TSE using transgenic PrP null mice carrying multiple copies of the human PrP gene including those from whole blood, buffy coat and plasma. WHO Bulletin OMS. Vol 74 1996 461 Memorandum Consideration should be given to convening a future WHO meeting regarding the infectivity of human non-CNS tissues of CJD patients such as those used for transplantation, in particular blood and blood products. It is noted that the pathogenesis of CJD may differ with the route of exposure and strain of agent. Diagnostic studies. A recent investigation on CSF marker proteins appears to provide the potential for a sensitive in-vivo test for CJD and related disorders. However, further studies on cases of CJD, other neu- rological disorders and control cases are required to establish the diagnostic value of this test in human and animal TSEs. The participants made the recommendations shown below. * Rapid, reliable tests with high sensitivity and specificity, particularly in the early or pre-clinical stages of illness, from easily obtained sources (e.g. body fluids) are urgently needed to diagnose both human and animal TSEs. * Further validation studies of currently available diagnostic tests as well as of those being developed, should be initiated. Biosafety studies. Further studies should be per- formed on current physicochemical protocols, alone and in various combinations, as well as to develop new protocols that completely inactivate infectivity from: - contaminated surgical instruments, equipment and accommodation; and - animal products and animal waste by using the most sensitive methods now available (e.g. transgenic mice). Research should be considered to examine any risks that may arise during conventional slaughter of TSE-infected but clinically healthy animals in abattoirs. The complete pathway of all tissues from food animals should be audited to determine their fate, whether for food, feed, medicinal/biological prod- ucts or devices, or other uses. Genetic studies. The studies outlined below should be carried out. * Extend the molecular genetic studies of the PrP gene (and other genes possibly associated with TSE) in humans and animals, especially cattle and sheep. * Study the extent of polymorphisms in the PrP gene of natural populations of human and other ani- mals, in order to identify genetic associations be- tween distantly related species (in progress). Treatment methods. There is an urgent need to de- velop a strategy for the prevention and treatment of human TSE based on genetic, biological and chemi- cal approaches which can be further developed as a result of findings from basic science research. It was noted, however, that some preventive strategies for some animal TSE are already in place. Use of in-vitro tests and animals for research. Every effort should be made to develop in-vitro tests for diagnosis and research, and studies requiring the use of laboratory and other animals should involve the smallest number of animals possible. Participants WHO Consultation on public health issues related to human and animal transmissible spongiform encephalopathies, Geneva, 2-3 April 1996 Dr A. Alperovitch, Paris, France; Dr R. Bradley, Addlestone, Surrey, England; Professor Dr H. Diringer, Berlin, Germany; Dr J. Gibbs (Co-Chairman), Bethesda, MD, USA; Dr F. Horaud, Paris, France; Dr J.W. Ironside, Edinburgh, Scotland; Dr H. Longbottom (Rapporteur), Canberra, Australia; Dr J. Losos (Chairman), Ottawa, Canada; Professor J.R. Pattison, London, England; Dr L. Schonberger, Atlanta, GA, USA; Professor P. Smith, London, England; Professor A. Somogyi, Berlin, Germany; and Professor M. Vandevelde, Innerberg, Switzerland. FAO: Dr Y. Cheneau and Dr P. Roeder. Office Intema- tional des Epizooties: Dr R. Reichard. European Commis- sion: Dr A.J. Wilson and Professor P. Peters. Observers: Professor H. Budka (Austria); Dr T. Baron and Dr 1. Capek (France); Dr E. Weavers, Ms B. Cannon, Mr D. Denham, and Dr J. Devlin (Ireland); Dr M. d'Alessandro (Italy); Dr Y. Kaji, Dr T. Kurata, and Dr E. Sanatani (Japan); Mr C. Feek (New Zealand); Dr L. Malychev (Russian Federation); Dr B. Hornlimann (Switzerland); Dr A. Wight, and Dr L. Robinson (United Kingdom); Dr B.W.J. Mahy, Dr T. Gomez, Dr K. Bernard, and Dr Clara Witt (USA): WHO Secretariat: Dr H. Nakajima, Dr Hu Ching-Li, Dr D.L. Heymann, Dr F.-X. Meslin (Secretary), Dr L.J. Martinez, Dr K. Stohr, Dr G.A. Clugston, Dr E. Griffiths, Dr F. Kaferstein, Dr S, Miyagawa, Dr C. Bolis, Dr A. Janca, Dr J. Orley, Dr M. Kaplan, Dr J.-C. Alary, Dr 0. Cosivi, Dr J. LeDuc, Dr M.C. Thuriaux, and Dr E. Tikhomirov. WHO Regional Office for the Americas: Dr S. Corber. WHO Regional Office for the Eastem Mediterranean: Dr M.H. Wahdan. WHO Regional Office for Europe: Dr G. Klein and Dr C.A. Van der Heyden. WHO Bulletin OMS. Vol 74 1996462 Creutzfeldt-Jakob disease and transmissible spongiform encephalopathies WHO Consultation on clinical and neuropathological characteristics of the new variant of CJD and other animal transmissible spongiform encephalopathies, Geneva, 14-16 May 1996 Dr M. Ben Hamida, Tunis, Tunisia; Dr R. Bradley, Addlestone, Surrey, England; Dr H. Budka, Vienna, Aus- tria; Dr L. Cartier, Santiago de Chile, Chile; Dr D.K. Dastur, Bombay, India; Dr J. Gibbs (Chairman), Bethesda, MD, USA; Dr Y.P. Guo, Beijing, China; Dr W.J. Hadlow, Ham- ilton, MT, USA; Dr T. Hemachudha, Bangkok, Thailand; Dr J.W. Ironside (Co-Rapporteur), Edinburgh, Scotland; Dr K. Kenney (Co-Rapporteur), Bethesda, MD, USA; Dr C. Keohane (Co-Rapporteur), Wilton, Cork, Ireland; Pro- fessor T. Kitamoto, Sendai, Japan; Dr D.C. Krakauer, Oxford, England; Dr C. Masters, Victoria, Australia; Pro- fessor I.P. Ndiaye Dakar, Senegal; Dr A.L. Taratuto (Co-Chairman), Buenos Aires, Argentina; Professor C. Weismann (Co-Chairman), Zurich, Switzerland; Dr R. Will, Edinburgh, Scotland; Dr G.A. Wells, Addlestone, Surrey, England. Observers: Mr. P. Jones (England), Dr T.C. Jones (USA), Dr Y. Kaji (Japan), Dr M.M. Kaplan (Switzerland); Dr H. Kretzschmar (Germany); Mrs E. Laurence (England); Dr K. Miura (Japan); Dr D.R.O. Morrison (Switzerland); Dr M. Pagel (England); Dr M.N. Ricketts (Canada); Dr L.B. Schonberger (USA); Dr C.J. Van Gelderen (Argentina). WHO Secretariat: Dr H. Nakajima, Dr Hu Ching-Li, Dr C.L. Bolis (Co-Secretary), Dr J. Emmanuel, Dr E. Griffiths, Dr D.L. Heymann, Dr A. Janca, Dr F.-X. Meslin (Secretary), Dr S. Miyagawa, Dr S.A. Orzeszyna, Dr L.L. Prilipko, Dr G. Rodier, Dr K. Stohr, Dr M. Thuriaux, Dr C. Dora, Dr S. Plianbangchang, Dr K. Morita. WHO Bulletin OMS. Vol 74 1996 463