NR ADKI
AU Dillner,L.
TI BSE linked to new variant of CJD in humans
QU British Medical Journal 1996 Mar 30; 312(7034): 795
KI BMJ. 1996 Apr 20;312(7037):1037-8. PMID: 8616362 BMJ. 1996 Mar 30;312(7034):790-1. PMID: 8608273 BMJ. 1996 Mar 30;312(7034):791-3. PMID: 8608274
PT news
VT
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. Some people are still presenting with CJD after having been infected with contaminated growth hormone manufactured from human pituitary glands.
The alarm generated by the new cases is due to the age of the people affected, the similarity of their clinical presentations, and the neuropathological findings on postmortem examination. Eight of the 10 people have died. A further two suspected cases were announced by the advisory committee this week but have not been confirmed.
"The average age of these cases was 27," said Dr Robert Will, head of the National CJD Surveillance Unit in Edinburgh. "The duration of their illnesses was more prolonged, with an average duration of 13 months compared with a mean in other types of six months. They all tended to present with anxiety, depression, and behavioural problems and within weeks or months developed unsteadiness, ataxia, and dementia. They had atypical electroencephalograms that were different from those found in sporadic cases."
Dr Will said that the cases shared consistent patterns of pathology, with large aggregates of prion protein in their brains that were far higher than those found in sporadic disease. Dr James Ironside, a neuropathologist at the CJD surveillance unit, said that the distribution of prion protein differed from that in BSE in that it was concentrated more in the cerebellum and basal ganglia than in the brain stem.
Six of the people affected with the disease started having symptoms in 1994 and four in 1995. None of them had worked in the farming industry, and the Spongiform Encephalopathy Advisory Committee said that no genetic link had been found. The committee said that it would expect the incubation period of this variant of CJD to be between five and 10 years.
"There may be some other factor in the mid-1980s that occurred to explain these cases and we don't know about it, but we can't think what it could be," said Professor John Pattison, chairman of the committee. "It drives us inevitably to the conclusion that the most likely risk factor is exposure to BSE."
Tests could take two years
Tests to establish whether the transmissible agent is related to BSE are being done through strain typing of necropsy material and could take up to two years. The BSE phenotype is thought to be identifiable in humans because it remains stable when it passes through other species.
The advisory committee has refused to put any figures on the numbers of people who could be affected by the new variant of CJD. It emphasises that it cannot confirm that BSE is responsible for the new cases and that if it is there are still no data on the dose needed for infectivity and the magnitude of any species barrier that should theoretically limit transmission from cattle to humans.
Dr Rosalind Ridley, head of the MRC comparative cognition team at the School of Clinical Veterinary Medicine in Cambridge, said that no one could predict whether there will be an epidemic of the disease. "Within 12 months we will know the answer. Either we will have more cases or we won't."
The initial concern that children might be more at risk of the disease than adults was largely based on the experience of kuru, a spongiform encephalopathy that was prevalent in Papua New Guinea until cannibalism was banned.
Kuru was transmitted through the ritual practice of mainly mothers and their children eating the brains of cadavers. Since young children were affected by the disease it was thought that the incubation time for CJD could be shorter than it was in adults. But in Britain the Spongiform Encephalopathy Advisory Committee maintains that the new variant of CJD has so far not shown this characteristic and that in the 10 people identified with the disease infection occurred mostly in early adulthood.
BSE was first identified in British cows in 1986 and is thought to have been caused by feeding them protein derived from sheep infected with scrapie in the form of meat and bone meal. This practice was banned in 1988.
ZR 0
MH Adult; Animal; Cattle; Creutzfeldt-Jakob Syndrome/*transmission; Encephalopathy, Bovine Spongiform/*transmission; Human; Zoonoses
SP englisch
PO England
OR Prion-Krankheiten D