Food and BSE: research

How is the cattle disease classified now?

WOAH distinguishes classical BSE, caused by the C-type agent and occurring in cattle after ingesting prion-contaminated feed, from atypical BSE, caused by H-type and L-type agents and believed to occur spontaneously in all bovine populations. Classical BSE was first detected in 1986, and WOAH states that control measures brought about its decline worldwide, that the incidence of both forms is now negligible and estimated to approach zero cases per million bovines, and that classical BSE is considered zoonotic because of its assumed link with the emergence of variant CJD. Only classical BSE is a WOAH-listed disease with official recognition of sanitary risk status, assessed against Chapter 11.4 of the Terrestrial Animal Health Code.

The consequence of that classification is practical. A country’s negligible or controlled risk status is not disturbed by an atypical case, because the atypical forms are treated as spontaneous events rather than as evidence of feed-borne exposure. The distinction rests on the assumption of spontaneous origin, which is inference from epidemiology and age distribution rather than a demonstrated mechanism.

What does a current case look like?

Scotland provides a recent worked example. The Scottish Government’s guidance, last updated on 26 August 2026, records that a case of classical BSE was confirmed on a farm in Dumfries and Galloway on 19 August 2026, that the animal was not presented for slaughter and that it did not enter the food chain. The same page’s update history records a confirmed case of atypical BSE in Dumfries and Galloway on 6 December 2024 and an earlier case in Ayrshire in May 2024. Suspicion must be notified immediately to the Animal and Plant Health Agency field service, and failure to do so is an offence.

Detection of a classical case four decades after the epidemic began is the system working as designed rather than a change in risk, but it also shows that passive surveillance in adult cattle remains the control that catches these animals.

Do sheep prions cross to human prion protein?

Wadsworth and colleagues inoculated transgenic mice overexpressing human prion protein with brain tissue from natural field cases of classical and atypical Nor98 scrapie, from sheep with experimental BSE, and from cattle with BSE. The mice were susceptible to BSE prions. Disease did not develop after prolonged post-inoculation periods in the mice inoculated with classical or atypical scrapie. The authors state that these data are consistent with the conclusion that prion disease is less likely to develop in humans after exposure to naturally occurring sheep prions than after exposure to epizootic BSE prions.

Read this against the primate result described on the biosafety hub, where one macaque inoculated with a classical scrapie isolate developed disease after about 110 months. The two experiments differ in host, in incubation time available and in isolate, and the species barrier they probe is modelled differently in each. Neither closes the question of sheep prion zoonotic potential, which is why atypical scrapie continues to be studied in humanised models.

Does destruction of specified risk material work?

Xu and colleagues tested composting, one of the disposal routes for specified risk material. In laboratory-scale composters using 45 kg of feedlot manure over 28 days, PMCA showed BSE prion seeding activity reduced by 3 to 4 log10 with chicken feathers added and 3 log10 without. In bin composters of about 2200 kg of manure run over 106 to 120 days and repeated in 2017 and 2018, seeding activity fell by 1 to 2 log10 in the centre and only 1 log10 at the bottom. A transgenic Tgbov XV mouse bioassay confirmed a similar reduction in infectivity. The authors suggest that enriching compost for proteolytic microorganisms by adding feathers could enhance degradation, and that temperature, the starting concentration of prions and the microbial population all affect the result.

A 1 to 2 log10 reduction is a reduction, not inactivation. The bin-scale result, which is closer to field practice than the laboratory-scale result, is the weaker of the two, and position within the pile mattered. Composting on these data belongs in a containment strategy rather than as a terminal inactivation step.

Related pages: decontamination, laboratory safety and the plain-language food and BSE.