What you need to know about mad cow disease (BSE)
Mad cow disease, known formally as Bovine Spongiform Encephalopathy (BSE), is a fatal neurological disease of cattle caused by an abnormal protein called a prion.
Ireland has had a long history with BSE, and while cases are now rare, surveillance remains active.
Most recently, a case of atypical BSE was confirmed by the Department of Agriculture, Food and the Marine (DAFM) in April 2026, identified through Ireland’s ongoing monitoring of fallen animals. The animal did not enter the food or feed chain and posed no public health risk.
Understanding BSE, how it spreads, what symptoms to look for, and how to respond, is important for every Irish farmer.
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What is “mad cow disease” (BSE)?
BSE is a prion disease that attacks the central nervous system of cattle, causing progressive and irreversible brain damage. It is always fatal.
The disease belongs to a group of conditions known as transmissible spongiform encephalopathies (TSEs), which affect both animals and humans.
BSE has a long incubation period, typically taking four to six years for infected cattle to show signs of the disease. This means an animal can carry the disease for years before any symptoms appear.
How did BSE start in Ireland?
BSE was first confirmed in cattle in the UK in 1986. The first case in Ireland was confirmed in 1989, when 15 cases were recorded.
Most experts agree that BSE was most likely spread by cattle eating feed that contained contaminated Meat and Bone Meal (MBM), a product made by rendering otherwise unused animal parts from carcasses.
Following the first diagnosis in Ireland, risk management measures were introduced, including legislation requiring vets, farmers, and all persons in charge of bovine animals to notify DAFM of any animal displaying clinical signs consistent with BSE.
A ban on the feeding of meat-and-bone meal to ruminant animals was introduced in 1990.
These controls have been effective. Ireland now holds WOAH negligible risk status for BSE, the lowest risk rating available, and the identification of occasional atypical BSE cases does not affect that status.
Mad cow disease symptoms in cattle
BSE symptoms typically develop slowly over a period of weeks or months. If you notice any of the following signs in your herd, contact the Department of Agriculture, Food and the Marine (DAFM) or your vet immediately:
- Change in behaviour or temperament
- Nervousness or apprehension
- Exaggerated reactions to touch or sound
- Weakness, particularly in the hind legs
- Reluctance to move through doors or near drains
- Aggression towards humans or other cattle
- Manic behaviour during milking
- Holding head low
- Difficulty rising
- Tremors under the skin
- Loss of body condition, weight, or milk yield
- Excessive nose licking
Cattle over the age of four that die on farm are routinely tested for BSE as part of Ireland’s national surveillance programme.
How do cows get mad cow disease?
BSE in cattle is caused by the consumption of contaminated feed containing abnormal prions. Historically, this occurred through meat and bone meal (MBM) produced from the carcasses of infected animals, which was incorporated into cattle feed. The use of MBM in ruminant feed has been banned in Ireland since 1990.
Classical BSE (C-type) is linked to contaminated feed. Atypical BSE, by contrast, is considered a rare, spontaneous occurrence in older cattle and is not associated with feed contamination. It is atypical BSE that has been identified in the handful of Irish cases in recent years.
Mad cow disease in humans: What is vCJD?
In humans, consumption of BSE,infected beef products, particularly brain and spinal cord tissue, has been linked to a rare and fatal prion disease called variant Creutzfeldt-Jakob disease (vCJD). This is distinct from classical CJD, which is not related to BSE.
Symptoms of vCJD in the early stages include depression, loss of coordination, and sensory disturbances.
As the disease progresses, dementia develops. vCJD is always fatal, typically within 13 months of onset. Around 233 cases have been reported globally since 1996, the majority in the UK.
The risk to the public from BSE today is considered very low. The controls introduced across Europe since the 1990s, including feed bans and the removal of specified risk material from the food chain, have been highly effective.
Milk and dairy products are not believed to transmit BSE.
BSE in Ireland today
Ireland holds WOAH negligible risk status for BSE. Cases today are rare and are typically atypical BSE a spontaneous form that occurs at very low rates in older cattle worldwide and is not linked to contaminated feed.
When cases are identified through DAFM’s fallen animal surveillance programme, the animals do not enter the food or feed chain.
Irish beef continues to be safely traded internationally, underpinned by the interlocking safeguards DAFM has maintained since the 1990s.
How Herdwatch can help with movement records and compliance
If BSE is suspected on your farm or on a farm you have traded with, accurate and up-to-date movement records are essential. Herdwatch makes it straightforward to stay on top of your compliance obligations:
Register OFF movements
Tap on the animals you plan to move and Herdwatch will notify CTS or APHIS instantly, keeping you compliant in seconds.
Register ON movements
Scan the barcode on the animal passport using the Herdwatch app. This notifies BCMS or APHIS and pulls down all animal details automatically.
Send correct data on time
Compliance is critical in a beef enterprise. Herdwatch ensures the correct movement data is submitted in a format accepted by BCMS or APHIS, on time, every time.
Report animal deaths
Select the animal that died and report it to BCMS through Herdwatch. You then have 7 days to return the animal’s passport to BCMS.
Download the Herdwatch app
Join over 21,000 Irish farmers using Herdwatch as their trusted cattle management software to manage their herds more efficiently and stay compliant with movement recording requirements.