Salmonella in Dairy Cattle: What You Need to Know

by Philip Jones

Salmonella remains one of the more challenging infectious diseases faced by dairy herds in the UK and globally. It poses not only a serious health risk to cattle but also a potential zoonotic threat to farm staff and visitors. Early identification, swift treatment, and robust biosecurity are key to keeping this disease in check.

What is Salmonella?

Salmonella is a group of bacteria that can infect both animals and humans. In cattle, the two most common strains seen in the UK are Salmonella Dublin (host-adapted to cattle) and Salmonella Typhimurium (a broader host range, often linked to environmental sources).

The disease can present in several forms, ranging from mild diarrhoea to sudden death, and the consequences can be severe, particularly in calves and stressed adult animals.

Clinical Signs

Salmonella infection in dairy cattle can affect animals of all ages, though the signs vary depending on age and immune status.

In Calves:

• Fever (often over 40°C)
• Profuse, watery diarrhoea, sometimes with blood or mucus
• Lethargy and inappetence
• Dehydration
• Septicaemia (in young calves), which can lead to sudden death
• Pneumonia – some infected calves may show respiratory signs

In Adult Cattle:

• Drop in milk yield
• Fever and depression
• Watery, often bloody, foul-smelling diarrhoea
• Abortion, particularly with Salmonella Dublin
• Weight loss and reduced appetite

In some cases, particularly with Salmonella Dublin, infected animals may show no signs but continue to shed the bacteria, contributing to spread within the herd.

Diagnosis

A firm diagnosis is important, not just for treatment, but for guiding long-term control measures.

• Faecal samples from affected animals are tested to confirm the presence and type of Salmonella. This is important in deciding which antibiotic is most appropriate.
• Post-mortem examination of any animals that die can be useful, with samples taken from intestines, lymph nodes, and other organs.
• Blood testing (serology) can help detect carrier animals, especially for S. Dublin.
• In outbreak situations, bulk tank milk testing may be used to monitor herd-level exposure.

Treatment

There is no one-size-fits-all treatment, and early veterinary involvement is crucial.

• Fluids and electrolytes are the most important treatment, especially in calves. Severe dehydration can kill quickly.
• Anti-inflammatories (like Finadyne, Ketofen or Metacam) can help reduce fever and improve comfort.
• Antibiotics may be used in severe or systemic cases but should be targeted based on vet advice and lab culture results. Overuse can worsen antimicrobial resistance and may not be effective in all cases.
• Isolation of affected animals is essential to limit spread.

Note: Salmonella is a reportable disease in the UK due to its potential risk to public health. Always consult your vet if you suspect Salmonellosis on farm.

Prevention & Control

Long-term control of Salmonella requires a multi-pronged approach, focused on reducing exposure, improving immunity, and preventing carrier animals from spreading disease.

1. Biosecurity

• Quarantine new arrivals for at least 3 weeks and test where appropriate.
• Control wildlife and vermin, especially birds and rodents, which can carry and spread Salmonella.
• Clean and disinfect calving and calf-rearing areas regularly.

2. Hygiene and Management

• Keep calving areas clean and dry.
• Ensure good colostrum management to improve calf immunity.
• Avoid overcrowding and reduce stress, especially during transport or housing changes.
• Use individual calf pens or small groups to limit disease spread.

3. Vaccination

• Vaccines are available in the UK against Salmonella Dublin. These may reduce clinical signs and shedding but will not eliminate infection.
• Vaccination is especially useful in high-risk herds or during/after an outbreak.
• Speak to your vet about whether vaccination is appropriate for your herd.

4. Monitor and Test

• Keep records of illness, abortions, and deaths – patterns can indicate a bigger problem.
• Consider regular testing for Salmonella if your herd has a history or you're seeing unexplained diarrhoea or abortions.
• Bulk milk testing can help monitor herd exposure to Salmonella Dublin.

Zoonotic Risk – Protecting People

Salmonella can infect humans, causing severe gastrointestinal illness. Vulnerable people – such as children, the elderly, pregnant women, or those with weakened immune systems – are particularly at risk.

• Always wash hands thoroughly after handling animals or working in calf areas.
• Use protective clothing, especially during outbreaks.
• Keep visitor access controlled, especially around calves.
• Be extra vigilant around abortion material, which can be highly infectious.

Final Thoughts

Salmonella is a disease that no dairy farm wants to deal with – but with good hygiene, management, and biosecurity, it can be kept under control. Work closely with your vet to develop a Salmonella control plan tailored to your herd, especially if you've had previous issues.

As always, if you notice sudden illness, diarrhoea, or abortions in your herd, don’t delay – give us a call. Early action can make all the difference.

If you have concerns about Salmonella on your farm or would like to discuss testing or vaccination options, please contact one of our vets.