Dr Catherine Conlon Where does BSE come from and what are the risks?

IN A MAJOR blow to Irish farmers and the beef industry, Irish beef exports to China have been stopped after a case of atypical BSE was detected in a bovine animal in Ireland.

This is the second time in recent years that Chinese markets have been stalled due to an atypical case of the disease. The Chinese market had only reopened in January after a three-year closure due to a previous BSE case in 2020.

The new case was discovered by Department of Agriculture vets, following tests on a ten-year-old cow that had been delivered for destruction.

Under a strict protocol agreement with China, beef exports have to be suspended on discovery of any BSE case until resumption is agreed by Chinese authorities.

Current exports to China are low, at about 2,000 tonnes of the 470,000 tonnes of Irish beef that Ireland has exported this year. The market has dropped from a high of €96million to China and Hong Kong in 2019, to just over €16 million by the end of August this year. However, the potential of the Chinese market for Irish beef exports is huge, with a population of 1.4 billion people.

In 2022, the UK made up almost half (43%) of the total value of Irish beef exports at €1.1 billion. But this market is increasingly precarious as the UK, post Brexit, is exploring other territories for cheaper beef – with Australia and New Zealand sending beef to the UK under a new free trade agreement this year.

The vulnerability of the UK market is a reason why Ireland is keen to expand into China and gain access to trade in Asia. This understanding colours recent visits to China by Tánaiste, Micheál Martin; a well-publicised visit to the world’s fourth largest importer of beef, South Korea by Agriculture Minister, Charlie McConalogue; and a visit to the Philippines and Malaysia by Minister of State for Agriculture, Martin Heydon.

Mr McConalogue said the discovery of atypical BSE should not affect Ireland’s wider markets. Ireland exports beef to 70 countries around the world – the export protocol in relation to BSE applies to the Chinese market only.

The Department of Agriculture stated that there was no danger at any stage of this animal entering the human food chain and no public health risk.

What is BSE?

Bovine spongiform encephalopathy (BSE) is a disease that affects adult cattle. BSE attacks the brain and central nervous system of the animal and is invariably fatal.

Commonly known as ‘Mad-Cow Disease,’ there is a long interval of about four to six years between cattle being infected with BSE to showing signs of disease. Symptoms include disorientation, clumsiness, and occasional aggressive behaviour towards other animals and humans.

Cows slaughtered on farm in Gloucestershire England due to suspected case of Bovine Spongiform encephalopathy BSE. Alamy Stock Photo Alamy Stock Photo

The World Organisation for Animal Health (WOAH) reports that animals can also show signs of depression, hypersensitivity to touch, twitching or tremors, abnormal posture, weight loss or decreased milk production. Affected animals display progressive behavioural or neurological signs.

Classical vs atypical

Classical BSE occurs through the consumption of contaminated feed. Whilst classical BSE was identified as a significant threat in the 90s, its incidence has markedly decreased in recent years, as a result of the successful implementation of control measures and is now estimated to be extremely low (close to 0 cases/ year worldwide).

Atypical BSE refers to naturally and sporadically occurring forms, which are believed to occur in all bovine populations at a very low rate.

Where does BSE come from?

BSE was first confirmed in cattle in the UK in 1986. The first case in Ireland was confirmed in 1989 when there were 15 cases confirmed. The Food Safety Authority of Ireland (FSAI) states that the expert view is that BSE was most likely spread by cattle eating food that contained contaminated Meat and Bone Meal (MBM).

MBM is produced by rendering, a process that involves animal products that are taken from the carcass being cooked for a long time to produce MBM. MBM was incorporated into cattle feed until it was banned in the 1990s.

The evidence shows that cattle can contract BSE if they are fed infected brain tissue, supporting the suggestion that BSE was transmitted to cattle through their animal feed.

Use of MBM in animal feed has been banned in Ireland since 1990, followed by an EU-wide ban on feeding MBM to all farm animals in 2001.

What danger is BSE to people?

BSE only develops in cattle but it belongs to a family of prion diseases, several of which can affect humans. A prion is a type of protein that can cause disease in animals and humans by triggering normally healthy proteins in the brain to fold abnormally. The functions of these normal prion proteins are still not completely understood.

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Morphological Pathology Laboratory, Prion diseases study. Brain sections. Alamy Stock Photo Alamy Stock Photo

The most commonly known disease in this group of prion diseases among humans is Creutzfeld-Jakob Disease (CJD). This is a rare and fatal form of dementia that normally occurs in individuals between the ages of 40 and 80.

CJD is not a new disease among humans, but in 1996, a new strain of CJD was discovered that predominantly affects young people. The protein that accumulates in the brains of people with this new form of CJD is similar to the protein found in cattle infected with BSE, rather than that found in classical CJD. The new illness in humans is therefore known as variant CJD or vCJD.

The occurrence of this form of CJD in the UK, where there was a high incidence of BSE, suggested that there might be a direct link between BSE and vCJD. There is evidence that people who developed vCJD were known to have eaten potentially BSE-contaminated meat products.

Researchers concluded that the most likely source of vCJD was human exposure to the BSE agent in infected meat products. As with BSE in cattle, vCJD is fatal to humans.

BSE-infected animals are found to have concentrations of the prion in a limited number of tissues such as the brain and spinal cord. These tissues are classified as Specified Risk Materials (SRM). The FSAI states that SRM from all cattle are systematically removed from the food chain and are disposed of by rendering, followed by incineration. This is the principal public health and food safety control.

Prevention and control in Ireland

The FSAI reports that BSE controls in Ireland since 1996 are very strict, with ‘layers of robust measures to ensure maximum consumer protection.’ These measures include a cattle movement monitoring system and inspection of all animals by a veterinary inspector prior to slaughter, ensuring that only healthy animals are slaughtered for human consumption.

There is a detailed post-mortem examination of all beef carcases and offals, with the removal of all SRM at the abattoir that is extensively checked by veterinary inspectors.

Controls at abattoirs and meat retail outlets are audited on an ongoing basis by the FSAI. All SRM undergoes separation, staining, separate storage and processing to ensure its total exclusion from human and animal food chains. All meat and bone meal products are excluded from the animal feed chain.

Despite the ‘robust and effective’ controls outlined by the Department of Agriculture, that allowed the case of atypical BSE to be identified, it remains to be seen how big a blow this single case of atypical BSE will be to the further development of the Irish beef trade in these giant Asian markets.

Dr Catherine Conlon is a public health doctor in Cork and former director of human health and nutrition, safefood.