Research and analysis

Epidemiological investigation of a single atypical BSE case in Dumfries and Galloway, Scotland (RBSE 24/00006)

Published 23 May 2025

Applies to Scotland

Executive summary 

In December 2024, Scotland’s Chief Veterinary Officer and the Animal and Plant Health Agency (APHA) confirmed a single case of atypical bovine spongiform encephalopathy (BSE) in a 19-year-old bovine in Dumfries and Galloway, Scotland. Atypical BSE is a natural and spontaneously occurring form of BSE that is reported with extremely low frequency in countries with solid active BSE surveillance programs (in countries with less robust surveillance these naturally occurring cases might not be detected). To date, there is no evidence that atypical bovine spongiform encephalopathy (BSE) is transmissible. There is no threat to food safety, to human health or to animal health as a consequence of this case. 

This case was identified through the UK active surveillance system, as required by UK legislation. Confirmatory testing at Weybridge TSE National Reference Laboratory indicated that the molecular profile was different from classical or L- type BSE and it was indistinguishable from H- type BSE which is a form of atypical BSE (WOAH and national reference laboratories have established Western immunoblot methods to discriminate H- and L-type variants from classical BSE). The clinical presentation of the case matched the known features of atypical BSE cases. 

The previous BSE atypical case in Great Britain (GB) was detected in March 2023. Over 186,333 cattle have been tested for BSE under the ongoing Active Surveillance programme between March 2023 and December 2024.  

An epidemiological investigation was carried out in both the holding of birth and the holding of death of the positive bovine animal. All the evidence indicates that this was a spontaneous atypical BSE case. The investigations have not detected any cause for concern that statutory official controls for BSE have been breached at any point in relation to this case or its herd of origin.  

The animal involved was humanely killed on farm and it was not destined to the food chain. Control measures were implemented including routine disposal of the entire carcass as category 1 animal by-product (ABP) material and identification and culling of the cohort and the offspring aged under 24 months of this atypical BSE case. BSE screening results for the cohort and offspring were negative. 

This report summarises the epidemiological investigations carried out in order to describe this atypical BSE case. 

Overview of atypical BSE 

The World Organisation for Animal Health (WOAH), differentiates between classical and atypical forms of BSE:  

• Classical BSE occurs through the consumption of contaminated feed. While classical BSE was identified as a significant threat in the 90s, its incidence has markedly decreased over the past years, as a result of the successful implementation of effective official control measures. 
• Atypical BSE refers to naturally and sporadically occurring forms, which are believed to occur in all bovine populations at a very low rate, and which have only been identified in older bovines when conducting intensive surveillance. To date there is no evidence that atypical BSE is transmissible. 

At the time of writing atypical BSE has not been directly associated with any human prion disease.  

Atypical BSE is not a WOAH-listed disease. Nevertheless, for the purpose of official recognition and annual reconfirmation of BSE risk status, WOAH members need to provide evidence that any bovines detected with atypical BSE have been completely destroyed or disposed of to ensure that they do not enter the feed or food chain. While to date there is no evidence that atypical BSE is transmissible to humans, measures to manage exposure risk in the feed chain continue to be recommended as a precautionary measure. 

The main clinical features of atypical BSE cases are: 

• atypical BSE is detected most frequently in bovines over 8 years of age  
• based on experimental studies, disease progression is generally slow, ranging from weeks to months. An animal may also present with an apparent sudden onset of disease (for example, unable to get up) even though its behaviour or temperament may have changed weeks or months ago

The European Food Safety Authority (EFSA) publishes yearly summary reports on surveillance for the presence of transmissible spongiform encephalopathies (TSE) (2021, 2022 and 2023).  

These publications confirm that reporting of atypical BSE cases occurs in countries with solid active BSE surveillance programs.

The reports also present a time-series analysis carried out over the last 10-year period showing a significant decreasing trend in the occurrence of classical BSE, whereas no significant trend for the 2 atypical BSE forms was found, pointing to the natural spontaneous occurrence of atypical BSE.

The occurrence of further classical BSE cases in many countries has been prevented by prohibiting the inclusion of processed animal protein in ruminant feed and subsequently in livestock feed. The ban of processed animal protein in ruminant feed also prevents recycling of an atypical BSE agent in feedstuffs.  

Case details 

The case reference is RBSE 24/00006. 

This case was identified through the UK active surveillance system, as required by UK legislation. Under this system, all fallen stock cattle (dead on farm not slaughtered for human consumption) aged over 48 months must be tested for BSE.  

On 29/11/2024 the Eurofins Forensic Services TSE testing laboratory, Risley, detected a BSE positive sample through routine national TSE statutory surveillance and testing of fallen stock cattle aged over 48 months, using the IDEXX EIA TSE rapid test on a sample from a 19-year-old bovine fallen stock, originating in a holding in Dumfries and Galloway, Scotland. 

Confirmation and typing of this case were based on western blot (WB) at Weybridge TSE National Reference Laboratory concluding that the agent had a molecular profile that is different from classical or L- type BSE and was indistinguishable from H- type BSE, which is a form of atypical BSE (WOAH and national reference laboratories have established Western immunoblot methods to discriminate H- and L-type variants from classical BSE). 

The index animal’s prion protein gene was sequenced, which did not identify any unusual polymorphisms that are not also seen in the normal cattle population. 

Epidemiological investigation 

The positive animal was born in 2005 in Perthshire, Scotland in a beef suckler herd. It was moved as a 2-year-old cow to another farm in Perthshire, where it resided until 2016. In 2016, the positive cow moved to a beef suckler herd in Dumfries and Galloway, where it remained until its death.  

The index case had been isolated in a field on her own for the past year due to her declining health, which was believed to be caused by old age. No clinical signs of BSE were observed. On 25/11/2024 this 19-year-old bovine was humanely euthanised on farm due to age-related deterioration. This clinical presentation matches the known features of atypical BSE cases. 

A BSE epidemiological questionnaire was completed for both the holding of birth and the holding of death of the positive bovine animal. No feed silos were or had been present in the holding of birth and where the case animal had spent the first 12 months of its life (period based on the scientific evidence, that classical BSE is transmitted via feed contaminated with prions given to a bovine animal during the first year of its life). 

Historic data on BSE testing confirmed that active BSE surveillance had been carried out regularly on both holdings and that no previous BSE cases had been recorded in either holding. Furthermore, no irregularities were identified in either of the 2 holdings.    

Control measures 

The positive animal was not presented for slaughter and did not enter the food chain. The entire carcass was routinely disposed of as category 1 ABP material, in common with all fallen stock bovines.  

The rearing and natal cohort, and the offspring aged under 24 months, of this atypical BSE case were identified. The surviving cohort consisted of one remaining live animal, and in addition there was one offspring aged under 24 months. These were placed under movement restrictions and subsequently culled. Brain samples were collected and screened for BSE. Both samples were found to be negative. 

There was no threat to food safety or human health. 

BSE testing and atypical cases in Great Britain 

Between 2007 and 2024 over 4.91 million cattle have been tested for BSE in GB. The previous BSE atypical case in GB was detected in March 2023, with over 186,333 cattle tested between March 2023 and December 2024.  

Concluding remarks  

Atypical BSE is a naturally and sporadically occurring non-contagious disease, which is believed to occur in all cattle populations at a very low rate.  Atypical BSE is distinct from classical BSE which is linked to infectious feed. 

The detection of this case is evidence that the surveillance system for detecting and containing BSE is solid and effective.  

The positive animal was detected through testing under the BSE fallen stock survey, part of the strict routine BSE official control and surveillance programme and was removed from the farm for disposal. This animal, as fallen stock, was not destined for the human food chain. There is no evidence that any TSE regulations have been breached in this case.  

There is no threat to food safety or human health and no further actions are necessary as a result of this isolated case. 

Annex 1: Summary of relevant TSE control measures  

Feed ban  

Feed controls were first introduced in the UK in 1988, when the cause of BSE was first epidemiologically linked to feed containing meat and bone meal. Since 1988 it has been prohibited to feed ruminant protein to ruminants in the UK. The 1 August 1996 is considered as the date of the effective reinforced feed ban when any animal protein was banned from all farm animal feed, with a few exceptions. A European Council Decision in 2000 (2000/76) extended the ban and provided harmonised BSE-related feed controls across all Member States. Current EU feed ban controls have been amended since then and are included in Regulation (EC) Number 999/2001. This Regulation has been assimilated in domestic legislation as it was on 1 January 2021.  

Great Britain National Feed Audit  

To confirm the effectiveness of the TSE feed ban controls in Great Britain, an inspection and sampling programme (the national feed audit) is undertaken throughout the animal feed chain.  

This includes imported feeds, bulk storage, production at feed mills, blending plants, mobile mixers and on farm mixers using fishmeal in feed production and livestock farms including home compounders.  

All incidents are rigorously investigated, and risk-based actions taken to prevent further marketing of contaminated feed into the feed chain and where necessary restriction of ruminant animals and removal of those animals from the food chain is carried out.  

Disposing of specific risk material 

Specific risk materials (SRM) are body parts of cattle or sheep that may contain significant amounts of prion in infected animals. Different animal parts are considered SRM, depending on whether they are of ovine or bovine origin and the age of the animal. SRM is banned from entering the food chain and is removed in abattoirs. The removal of SRM is confirmed at a post-mortem inspection. 

Animals are also subject to an ante-mortem inspection on arrival at the abattoir. 

In this case, the animal was culled on farm and was not destined to the food chain. As fallen stock, the entire carcass was category 1 animal by-product and was disposed of. 

Testing cattle for BSE 

The UK has a robust surveillance programme for BSE, which includes both active and passive surveillance. 

Under the active surveillance programme approximately 100,000 BSE tests are undertaken annually in GB. Bovine animals are tested for BSE if they are born in the UK or in an EU country other than Romania or Bulgaria and:  

• the animal is aged over 48 months and showed signs of sickness when examined by a veterinarian before death (ante-mortem inspection) 
• the animal is aged over 48 months and has been sent for emergency slaughter (for example, casualty animals which do not appear to be unwell, but have broken a leg or suffered some other injury)  
• the animal is aged over 48 months and is fallen stock, that is, their death was not due to being slaughtered for human consumption  
• the animal is older than 30 months and killed for the farmer’s private consumption. 

In addition, our active surveillance programme requires BSE testing of bovine animals:  

• slaughtered for human consumption at abattoir if they were born in Romania, Bulgaria, or any non-EU country and they were older than 30 months and healthy at the time of slaughter  
• that are fallen stock, were sent for emergency slaughter or showed signs of sickness when examined by a veterinarian before death that were born in Romania, Bulgaria or any non-EU country and were older than 24 months at the time of death

Under the passive surveillance programme all bovines suspected of having clinical BSE must be immediately reported for investigation to the competent authority. If the investigation determines that BSE cannot be ruled out, the animal is culled and samples are collected for testing. 

Ban on on-farm burial of fallen stock  

Since May 2003, it has been illegal to bury fallen stock (dead animals) on farms throughout the European Union (of which the UK was a member or continued to adhere to the specific regulations during ’the transition period’ until 31 December 2020) under the EU Animal By-Products Regulation. This prohibition has been assimilated in domestic legislation from 1 January 2021. 

A derogation exists within remote areas for burial to occur, however the farm concerned is not within any derogated areas.