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It has long been accepted that the pattern of occurrence of scrapie—the form of spongiform encephalopathy associated with sheep—is determined mainly by maternal transmission, and this view has had a profound influence on policy decisions in the control of bovine spongiform encephalopathy and on public concern over the risk to human health from this disease. The occurrence of maternal transmission is, however, not predicted by modern knowledge of the aetiology of spongiform encephalopathy, and even though claims of maternal transmission have been reiterated frequently in the literature, re-examination of the source data reveals that these data are extremely scanty, unreplicated, and probably subject to ascertainment bias. The probability of maternal transmission of spongiform encephalopathy in any species should be viewed with the greatest scepticism. In assessing the risk to human health of the epidemic of bovine spongiform encephalopathy (BSE) in the United Kingdom, the Southwood Committee accepted the view that in scrapie (the spongiform encephalopathy occurring in sheep) “there is transmission of scrapie from the infected ewe to lamb.”1 Maternal transmission means the infection of the lamb by the dam through a mechanism which is specific to this biological relationship—prenatal or perinatal transplacental transfer of infective agent or infection through milk, saliva, or the close contact of birth and suckling. The House of Commons Agriculture Committee on BSE concluded that if maternal transmission also occurred in bovine spongiform encephalopathy then “its elimination will be much harder and its implications for humans much more uncertain” and “the policy implications would be substantial.”2 In 1989 a long term study was initiated to monitor the possible occurrence of maternal transmission in bovine spongiform encephalopathy.3 Alarm in the general public was fuelled by Professor Lacey, who promulgated the view that for bovine spongiform encephalopathy “vertical transmission should prolong the epidemic into …

The identification of 10 cases of Creutzfeldt-Jakob disease, which seem to represent a new variant,1 and the announcement by the Spongiform Encephalopathy Advisory Committee (SEAC) on 20 March that these cases could be linked to exposure to bovine spongiform encephalopathy, have caused great concern. Patients are worried about the risks of developing Creutzfeldt-Jakob disease not only from eating beef but also from medicinal products of bovine origin and are looking to doctors, pharmacists, and pharmaceutical companies for reassurance. The risk of transmission of bovine spongiform encephalopathy via medicinal products depends on whether the infective agent is a human pathogen and on the level of exposure to the agent. To date, no epidemiological link has been made between any spongiform encephalopathy that is transmissible in animals and human disease, despite exposure of humans to the scrapie agent for at least 200 years. This suggests that the risk of transmission to humans is small.2 Measures aimed at minimising exposure to transmissible spongiform encephalopathies via medicinal products were introduced soon after the report of the …

EDITOR,—In their article looking at the possibility of maternal transmission of spongiform encephalopathy R M Ridley and H F Baker analyse previously published information and conclude that natural sheep scrapie has a genetic basis.1 Of course this is so. Because of the absence of nucleic acid within the infective particle, host genome is required for the pathogenesis of the disease,2 and it follows that such genes are inherited in various ways. This in no way negates the well established observations that the transmissible spongiform encephalopathies are due to infectious agents which are acquired by vulnerable hosts in a variety of ways, including maternal transmission.3 Maternal transmission cannot sustain the disease …

The occurrence of Creutzfeldt-Jakob disease in British dairy farmers possibly exposed to cattle with bovine spongiform encephalopathy has focused attention on the possibility of a causal link between the two diseases. We briefly review the currently available epidemiological evidence. The table shows the incidence of Creutzfeldt-Jakob disease in France, Germany, Italy, the Netherlands, and Britain. The data are based on registries in the countries, which have used similar methods of surveillance and criteria for diagnosis since the start of a European collaborative study in …

Anxieties over the possibility that material from or contact with cows infected with bovine spongiform encephalopathy might cause Creutzfeldt-Jakob disease revolve around three questions. Could it happen? Bovine spongiform encephalopathy in cows, scrapie in sheep and experimental animals, and Creutzfeldt-Jakob disease are all caused by the same class of pathogen and are more accurately called prion diseases.1 Human prion disease is rare, but the public health importance of prion disease far exceeds its rarity for the following reasons. It has been transmitted experimentally to various animal species1 2 (bovine spongiform encephalopathy has been transmitted experimentally in primates), and accidental person to person transmission has occurred.3 In addition, it has been shown that prion disease can be transmitted orally by the ingestion of infected foodstuffs or infected tissues.4 5 The …

Risks from British beef on the bone were declared negligible this week by the government's Spongiform Encephalopathy Advisory Committee (SEAC), one year after it was banned asa possible source of human infection with new variant Creutzfeldt-Jakob disease ( BMJ 1997;315:1560). Ministers are now consulting about lifting the statutory restriction on its sale. …

The British government is coming under pressure to order surveillance of sheep to see if flocks are infected with bovine spongiform encephalopathy (BSE). Professor Jeffrey Almond, a member of the government's Spongiform Encephalopathy Advisory Committee (SEAC), spoke this week of a “distinct possibility” that BSE could be found in sheep and recommended more extensive research. Professor Almond, a virologist and professor of microbiology at the University of Reading, is to head a new subcommittee of SEAC to produce specific recommendations for a programme of research. He was speaking on BBC radio's Farming Today after an article in Nature (1998;395:6-7) quoted a member of SEAC as saying that if BSE has passed into the sheep population “we could be facing a potential national emergency.” Professor Almond says that the possibility remains that BSE was introduced into the …

Donated blood supplies in Britain are to be treated to reduce the risk of patients being infected with new variant Creutzfeldt-Jakob disease (CJD) because of a theoretical risk that it could be transmitted via the white blood cells. The Department of Health is acting on the advice of its scientific advisers on the Spongiform Encephalopathy Advisory Committee (SEAC). As a precautionary measure, blood will go through a process of leucodepletion, which removes up to 95% of white blood cells. The process, which will cost £70m ($110m) …

EDITOR—Bowser is right to attempt to provide an update of European Union (EU) policies regarding bovine spongiform encephalopathy and pharmaceuticals.1 Unfortunately his letter misses the main concern of my earlier letter2: where is the evidence supporting any of the EU's policies on bovine spongiform encephalopathy and pharmaceuticals? Bowser is wrong to state that amendments to the EU directive on spongiform encephalopathy will not affect drugs. The commission's decision of 30 July (not 29 July as he stated) …

EDITOR,—On 20 March the Spongiform Encephalopathy Advisory Committee in Britain issued a statement regarding 10 cases of Creutzfeldt-Jakob disease that showed a previously unrecognised and consistent pattern of disease.1 The committee concluded: “in the absence of any credible alternative the most likely explanation at present is that …

Children are no more susceptible to the new variant of Creutzfeldt-Jakob disease than the rest of the population, the British government announced this week (see pages 790, 791, and 854). The Spongiform Encephalopathy Advisory Committee considered further genetic information on the 10 new cases of CJD reported last week and consulted with a paediatrician, immunologist, and gastroenterologist before reaching its decision last weekend. It repeated its view that the most likely explanation for the 10 new cases is exposure to the agent that causes bovine spongiform encephalopathy in cattle that occurred before the ban on the use of cow offal was introduced in 1989. In accepting the committee's opinion, the government has for the first time acknowledged that BSE could be transmissible to humans. There were 40 cases of CJD in Britain last year according to government statistics, compared with 54 in 1994. About 15% of these have a genetic basis; others are sporadic, for which no cause is known—these usually occur in people aged over 60. …

EDITOR,—We are pleased that, in the commentary on our article on the myth of maternal transmission of spongiform encephalopathy, R G Will agrees that maternal transmission does not occur in human or experimental forms of spongiform encephalopathy and that the only circumstance in which it requires serious consideration is natural scrapie.1 The genetics of natural scrapie and the genetics of susceptibility to experimental transmission of scrapie in sheep differ. The characteristics and quantity of the agent, the …

Creutzfeldt-Jakob disease has now been identified in four farmers and two adolescents in Britain, where its bovine spongiform counterpart has been epidemic for the past several years. Is there a connection? This question is being discussed by many different groups according to pre-existing biases and professional goals, as might be expected for so controversial and potentially explosive a topic. The media has in the main sounded alarm bells because its goal is to produce an exciting story; the government has taken a low key, cautious approach because its goal is to prevent unwarranted panic; and medical science has been somewhat unpredictably divided in its evaluation, depending at least in part on individuals' distaste or flair for publicity. In fact, no one can …

Whenever an unusual case of Creutzfeldt-Jakob disease is reported in Britain someone asks: “Is this the beginning of the end--are we all going to die of BSE?” It is a commonly held view that the incubation period for spongiform encephalopathy in humans is at least one to two decades. This is a misconception. For kuru, when the dose of infectivity by the oral route was high the minimum incubation period was less than four years and the median ranged from less than five years to nine years (judged by the minimum ages at onset at the height of the epidemic).1However, the incubation period can be as long as 30 years (judged by the ages of the most recent cases).2 While experimental transmission …