NR ABOS
AU Bradbury,J.
TI Maternal transmission of BSE demonstrated in cattle
QU Lancet 1996 Aug 10; 348(9024): 393
PT news
VT
Results released last week by the UK Ministry of Agriculture, Fisheries and Food indicate that bovine spongiform encephalopathy (BSE) can be passed from cow to calf. In the experimental animals, maternal transmission rates were about 10% (panel). The results provide some evidence that only cows in the last 6 months of infection transmit BSE to their offspring, and MAFF calculates that the average cow-calf transmission rate over the 60-month incubation period may be as low as 1%. MAFF says that this figure is "not significant enough to maintain BSE levels". According to the Spongiform Encephalopathy Advisory Committee "there is no case for changing its recommendations in relation to milk, meat, blood or any other product".
Researchers have long been concerned that BSE might be transmitted vertically as well as through contaminated foodstuff. For scrapie, a transmissable spongiform encephalopathy (TSE) of sheep, there is general acceptance of maternal transmission. Stephen Dealler, consultant medical microbiologist at Burnley General Hospital, UK, points out that the pattern of BSE incidence in the national herd fits best a model of transmission that includes an element of maternal transmission.
Prof John Pattison, SEAC chairman says that the MAFF results are potentially good news. "They suggest that the ban on contaminated feedstuff has been much more effective than had been thought. We may have fewer cases of BSE than expected in the future", says Pattison, "and, with this new information, we can more accurately target animals to be culled".
[Image]
The study provides no indication as to how maternal transmission may have occurred. It could have been in utero, at birth, or soon after birth, says SEAC. Unlike scrapie, no infectivity in the placenta of BSE-infected animals has been demonstrated. Neither blood nor milk from BSE-infected animals has been shown to be infectious in existing tests. Some scientists, including Dealler, believe that we should not be complacent about these negative results. In the case of milk, Pattison says that the lack of evidence for transmission of infectivity in milk in kuru (a human TSE) and scrapie is reassuring. In the MAFF study, he says, there are no data to suggest that the rate of maternal transmission is any greater in beef suckler calves who have prolonged exposure to their mother's milk than in dairy herds where calves do not drink mother's milk.
One of the next milestones in the BSE story may well be when experiments testing whether variant Creuztfeldt-Jacob disease (CJD) cases (Lancet 1996; 347: 921-25) carry BSE-infectious material are completed - this is unlikely to be until next year, says Pattison. Moira Bruce (Institute for Animal Health, Edinburgh, UK) is innoculating mice with material from variant CJD patients' brains. Different mice strains demonstrate characteristic disease incubation times and lesion profiles that depend on both the mouse strain and on the source of infective material (ie, BSE, CJD, or different strains of scrapie). In separate experiments, John Collinge (Imperial College London, UK) is injecting material from patients into transgenic mice expressing human prion protein.
ZR 1 Zitat
MH Animal; Cattle; *Disease Transmission, Vertical; Encephalopathy, Bovine Spongiform/*transmission
SP englisch
PO England
OR Prion-Krankheiten 2