Variant CJD and mad cow disease

Bovine spongiform encephalopathy, a fatal prion disease of cattle, was first identified in two British cows in 1986; they had probably been infected in the 1970s. The likeliest cause was cattle feed made with meat-and-bone meal containing infected material from cows or sheep, and the epidemic spread as such feed was given to calves. More than 184,000 British cattle died of the disease between 1986 and 2015, in more than 35,000 herds, and cases peaked in 1993 at nearly 1,000 a week.

Because of the cattle epidemic, the UK restarted surveillance of Creutzfeldt-Jakob disease in 1990. Neurologists and neuropathologists referred suspected cases, relatives answered a standard questionnaire about risk factors, and about 70 percent of suspected cases had a neuropathological examination. Similar studies ran in France, Germany, Italy and the Netherlands from 1993 to 1995.

On 6 April 1996 Robert Will and colleagues reported in the Lancet ten British cases with a new neuropathological profile. The patients were young, their clinical findings were unusual, and they lacked the electroencephalogram pattern typical of CJD. No similar cases had been found in the other European countries. The authors called it a new variant of CJD, possibly unique to the UK, and wrote that a causal link to BSE was possible but could not be confirmed on that evidence alone. Molecular and animal studies later confirmed BSE prions as the source.

Human cases rose to a peak in 2000 and then declined. By 2024 there had been 232 recognized cases worldwide: 178 in the UK, 28 in France and smaller numbers in ten other countries. Every definite case tested but one carried two copies of methionine at codon 129 of the prion protein gene. Three people developed the disease after blood transfusion. The last known British patient died in 2016.