LONDON, Oct. 16 (UPI) -- One-in-2,000 people in Britain, roughly 30,000 people, may be silent carriers of the human form of "mad cow disease," researchers say.
Variant Creutzfeldt-Jakob Disease is the human form of bovine spongiform encephalopathy or, mad cow disease, and one of the family of mainly neurodegenerative diseases known as spongiform encephalopathies. The diseases afflict animals and humans and are widely accepted as resulting from the toxic build-up of an aberrant form of a normal cellular protein, the prion protein.
Dr. Sebastian Brandner, one of the study authors and head of the Division of Neuropathology at Queen Square in London, said bovine spongiform encephalopathy was common, with more than 36,000 cases in the peak year of the cattle epidemic in Britain in 1992. However, variant CJD has remained rare, with 177 cases in the Britain to date, 51 in the rest of the world, 27 in France, and only one in the past two years, Brandner said.
Sporadic CJD, the "usual" form of CJD, was first described early last century and is found worldwide, with an annual incidence of around 1/1,000,000. Prion infectivity is notoriously difficult to inactivate and sporadic CJD had been shown to be transmissible by neurosurgery in case studies published as long ago as 1974, the researchers said.
Brandner and colleagues studied appendix samples from 32,441 people and found 16 tested positive for vCJD.
Brandner said the peak of mad cow disease was in 1992, and the peak of the human form of mad cow disease occurred in 2000 -- suggesting an 8-year incubation period for the disease.
However, the research revealed there were at least three different forms of the prion protein linked to vCJD, which might explain why more people haven't become sick with the disease, the study said.
The findings were published in the British Medical Journal.