Mad cow disease kills vegetarian.
Miss Clare Tomkins, aged 25, from Tonbridge, Kent, died from new variant Creutzfeldt-Jakob Disease, the illness thought to be contracted from contaminated beef.
Miss Tomkins' illness challenged the theory because she stopped eating meat a year before the first case of mad cow disease was diagnosed in cattle.
Meanwhile scientists warned that the disease could be harboured by animal species, such as mice and rats, which were not known to succumb to it.
The findings raise the alarming possibility that poultry and pigs exposed to BSE-contaminated feed may have been infected with the disease.
The new research carried out by Richard Race and Bruce Chesebro, of the National Institute of Allergy and Infectious Diseases, Hamilton, Montana, in the US, involved injecting the infectious agent for hamster scrapie - a CJD-like disease - into the brain s of mice.
The mice developed no symptoms but a year later the scientists found that mice tissues could be used to infect hamsters with scrapie.
The scientists wrote in the journal Nature: "This unexpected and prolonged survival of a foreign scrapie agent raises the possibility that BSE infectivity might persist in various `resistant' species exposed to BSE-contaminated feeds."