Maternal BSE risks are lower than thought
RISK of maternal transmission of BSE is lower than previously thought, according to analysis of MAFF trial results.
Interim results of the trial, published by MAFF in July last year, suggested there was a 10% risk of maternal transmission.
But an analysis by Roy Anderson, head of Oxford Universitys centre for the epidemiology of infectious diseases, shows an 8% risk of maternal transmission for calves born in the last 150 days before their dams developed BSE symptoms.
When applied to the national herd, the findings indicate that less than 1% of calves born to BSE infected dams are likely to develop the disease.
Prof Anderson also suggested that some calves have a genetic predisposition to the disease, but to develop the disease they would have to be exposed to BSE contaminated feed.
The ban on the use of meat and bonemeal in all livestock feed, imposed in Mar 1996, effectively meant genetically susceptible animals would not now fall victim to BSE.
With the government about to embark on its selective cull of animals, considered most at risk of developing BSE, Prof Anderson said he believed any further cull based on maternal transmission would be uneconomic.
MAFF would not comment on the results until its own analysis of the trials was complete.
The NFU said the greatest possible reassurance given by Prof Anderson was his belief that only about 150 animals under 30 months were likely to eventually develop BSE.
Sir David Naish, NFU president, said: "This analysis is encouraging as it indicates that maternal transmission – either of BSE or a genetic predisposition to developing BSE – will not extend the epidemic."
But Tony Bailey, Country Landowners Association director of policy, said that proof of maternal transmission could affect the governments aim to lift the export ban for animals born after Aug 1, 1996.
"Maternal transmission casts a doubt on the premise that any animal born after this date would be free from BSE," he added.
Both he and Lib Dem rural affairs spokesman, Paul Tyler, attacked the government for failing to provide an authoritative statement on Prof Andersons findings.
lThe EUs scientific veterinary committee is not expected to deliver its opinion on maternal transmission until next month at the earliest.