Antibiotics

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What are antibiotics, how do they work, and why are they prescribed for companion animals and livestock

Antibiotics are specialised medicines that target and eliminate bacteria that cause illness or infection. They work by either destroying the bacteria directly or by inhibiting their ability to reproduce and spread. In both companion and food producing animals antibiotics are essential in treating a variety of bacterial diseases, ranging from skin infections to pneumonia or mastitis. In the UK, veterinary surgeons prescribe antibiotics for companion animals and farm animals to ensure animal health and welfare, control infectious outbreaks, and prevent suffering. All antibiotics must be authorised and supplied by a veterinary surgeon following an appropriate clinical assessment. Their use is closely regulated, and antibiotics should only be prescribed based on a clear veterinary diagnosis with the aim of minimising unnecessary use and the risk of developing resistance.

How does antibiotic use in animals differ from human use, and what risks and considerations are involved?

While both humans and animals are given antibiotics to treat bacterial infections, there are notable distinctions in their use. Importantly, some antibiotics are strictly reserved for human medicine and are not permitted for use in animals to protect their effectiveness for treating human diseases. Conversely, certain antibiotics may be approved for animal use but not for humans.

The dosage, the route of administration and the frequency of treatment are tailored to the specific animal species, their weight and health condition. In farming, it is sometimes necessary to treat entire groups of animals to prevent the spread of disease,  a practice known as metaphylactic use. Metaphylactic use refers to the administration of antibiotics to a group of animals when some individuals within the group are showing signs of illness, with the aim of treating sick animals and preventing the disease from spreading further.

Metaphylactic use is also occasionally used in human healthcare settings. For example, during a meningitis outbreak in a school or university, antibiotics may be given to close contacts of affected individuals to prevent further cases, even if not everyone is currently showing symptoms.

One concern is that antibiotic residues could remain in animal products such as meat, milk or eggs, potentially entering the human food chain. To safeguard against antibiotic residues in food, strict regulations require withdrawal periods between antibiotic treatment and the collection of animal products. In addition, regular monitoring and testing programs are carried out to ensure residue levels remain below safe limits.

Overuse or improper use of antibiotics in animals can also lead to bacteria developing resistance, which poses risks to both animal and human health. Therefore, strict regulations, veterinary supervision and thorough monitoring are vital to ensure antibiotics are used carefully and responsibly.

How does antibiotic resistance develop and spread between animals and humans, and what steps are taken to prevent it?

Antibiotic resistance occurs when bacteria change or adapt in ways that allow them to survive exposure to antibiotics that would normally kill them or stop their growth. This can happen through genetic mutations or the exchange of resistance genes between bacteria. Overuse or misuse of antibiotics accelerates this process.

Once resistant bacteria emerge in animals, they can spread to humans through direct contact, contaminated food or other environmental pathways such as water sources. To address this, veterinary surgeons are encouraged to only prescribe antibiotics when truly needed, based on a clear diagnosis and to use the correct dose and course for the individual animal or groups of animals. Farmers and animal owners are encouraged to follow the advice of their veterinary surgeon when using antibiotics to ensure that use is responsible. Enhanced biosecurity, hygiene and surveillance programmes help to prevent the need to use antibiotics and therefore help reduce the risk of resistance arising. Education, training and international cooperation are all part of the effort to prevent and control resistance.

What measures help reduce the need for antibiotics on farms?

Reducing the need for antibiotic use in farm animals relies on a combination of proactive animal health measures. Vaccination programmes are among the most effective, protecting animals against common infectious diseases and lessening the likelihood of outbreaks that would require antibiotics. NOAH has created the Livestock Vaccination Guidelines to support veterinary surgeons in tailoring vaccination programmes that are specific to the farm (which consider the management system, animals and disease status of the herd or flock). Good nutrition, proper housing and maintaining low-stress environments also strengthen an animals’ immune system and improve their resilience to infectious diseases. Enhanced biosecurity, including controlling farm visitors, disinfecting equipment, and separating or quarantining sick animals helps to prevent disease from entering or spreading within a herd or flock. Regular veterinary check-ups, record-keeping and early detection of illness are key. By focusing on preventative care and sound management practices, farms can maintain productivity and animal welfare while using antibiotics only as a last resort.

Which UK authorities oversee compliance with antibiotic use guidelines?

The UK has established strict guidelines to ensure antibiotics are used responsibly in animals, aiming to protect both animal and human health. The Veterinary Medicines Directorate (VMD) sets the standards for use, including prescribing rules, record-keeping and residue testing. The Food Standards Agency (FSA) works alongside the VMD to ensure food safety and monitors compliance with withdrawal periods and residue limits.

How does the VMD Veterinary Antimicrobial Resistance and Sales Surveillance (VARSS) report track antibiotic use?

The annual Veterinary Antimicrobial Resistance and Sales Surveillance (VARSS) report, published by the VMD, is the UK’s primary source of data on antibiotic use in animals. The report provides comprehensive statistics on sales and usage of antibiotics in livestock, as well as detailed analysis of antimicrobial resistance trends across multiple species.

Over the last decade, the VARSS report has tracked a significant reduction in antibiotic use within UK livestock sectors, with usage falling by more than half. This achievement reflects the collaborative efforts of vets, farmers, and industry bodies, supported by targeted initiatives that encourage responsible medicine use. The report benchmarks current sales and usage figures against previous years, identifies areas for improvement, and offers guidance for ongoing stewardship. Its findings help inform policy, support research, and are vital in safeguarding both animal and public health.

What is the animal health industry doing to promote responsible antibiotic use?

The animal health industry, working in collaboration with veterinary professionals, farmers and government agencies, plays a vital role in encouraging responsible antibiotic stewardship. NOAH actively supports initiatives such as the Responsible Use of Medicines in Agriculture Alliance (RUMA), which brings together stakeholders to set practical guidelines, develop stewardship principles and track industry progress through transparent reporting. Additionally, the Animal Medicines Best Practice (AMBP) programme has been developed by NOAH in collaboration with stakeholders across the food supply chain to ensure coordination and consistency in the approach to the responsible use of medicines. As part of this initiative, training modules on the responsible use of antibiotics are available for dairy, beef, sheep and pig farmers.

In addition, NOAH has endorsed and participated in campaigns like the Antibiotic Amnesty, which encourages the safe return and disposal of unused or expired antibiotics to prevent misuse and environmental contamination. Through training, awareness campaigns and the promotion of preventative measures such as vaccines and enhanced biosecurity, the industry aims to ensure that antibiotics remain effective for both animals and people.

Further Reading

For more information, please see the following sources:

• Responsible Use of Medicines in Agriculture Alliance (RUMA) Website (Available at: RUMA – Responsible Use of Medicines in Agriculture Alliance)
• VMD Connect Antimicrobial Resistance (Available at: Antimicrobial resistance)
• Royal Pharmaceutical Society Antibiotic Amnesty (Available at: Antibiotic Amnesty)
• Food Standards Agency (FSA) Milk Hygiene and Antibiotic Residues (Available at: Milk hygiene and antibiotic residues | Food Standards Agency)
• RCVS Knowledge Antimicrobial Resistance Hub (Available at: AMR Hub – RCVS Knowledge)
• Farm Vet Champions Responsible Antibiotic Use for Veterinary Professionals (Available at: Farm Vet Champions – RCVS Knowledge)