Salmonella
Controlling salmonella on farm for pig health and food safety.
Why salmonella matters
Salmonella is a zoonosis: it can pass from animals to people through the food chain. Pigs can carry salmonella without showing any signs of illness so it can only be found and controlled through monitoring.
- Salmonella is the second most common cause of bacterial food poisoning in people worldwide, with up to 50,000 cases a year in the UK.
- Monophasic Salmonella Typhimurium has increased sharply in pigs and people across Europe since 2007 and its resistance to antibiotics is growing.
- Most commercial pig farms carry some salmonella, but Typhimurium and monophasic Typhimurium are the types of most concern.
- Salmonella from pigs can spread beyond the farm in meat, slurry and dust, to wildlife and other livestock, especially poultry.
The good news: the hygiene improvements that control salmonella also reduce other diseases on the farm and can improve productivity. These on farm measures complement the comprehensive controls undertaken by processors and the wider supply chain to minimise any food safety risks.
The Scottish Salmonella Scheme
The Scottish Salmonella Scheme monitors and controls salmonella levels in Scottish pig herds. It is one of the five pillars of the Scottish Pig Health Scheme, which is part of the Quality Meat Scotland (QMS) Pigs Assurance Scheme.
How it works
- Sampling: samples are collected at the abattoir every quarter from all members’ herds. Scottish Pigs collects meat juice samples for the scheme.
- Scoring: each farm is given a salmonella score.
- Reporting: the score is included in the farm’s quarterly Wholesome Pigs Scotland abattoir health monitoring report, which goes to the producer and their vet.
- Action: any farm with an above-average score is visited, and a control plan is put in place to bring salmonella levels down.
Who must take part
Under QMS Pig Standard 2.11, units slaughtering pigs in Scotland must take part in the Scottish Salmonella Scheme. Finishing units must also be members of an abattoir health monitoring programme, such as Wholesome Pigs Scotland (Standard 3.16).
A long record of results
Scotland has monitored salmonella in pigs for more than 20 years. Under the UK Zoonoses Action Plan, Scotland met its target of a 25% reduction over the first three years, and by 2005 the level of meat-juice positives in Scottish herds was almost four times lower than in English herds (BPEX, 2005).
Controlling salmonella on farm
There are two goals: stop new infection getting in, and reduce the salmonella already there. If your score is high, your vet will help you draw up a control plan for your unit. Good hygiene comes first – other measures only work once it is in place.
Replacement pigs
Source from salmonella-free stock where possible, from as few units as possible. Keep new pigs separate for four weeks, and consider testing them on arrival. In the long term, aim for a closed herd.
Pig flow
Farrow in batches and mix piglets only at weaning. Keep groups together, minimise moves, and run grower and finisher houses all-in, all-out. Don’t hold back sick or small pigs into later batches.
Cleaning & disinfection
Pre-soak with detergent, clean and dry before disinfecting, and remove pooled water from troughs. Use approved disinfectants at the right strength, and allow as much drying and empty time as possible.
Rodents
Mice are a bigger salmonella risk than rats and can multiply infection. Keep them away from feed and bedding, bait where you see activity, and proof buildings and drains.
Feed
Ask suppliers for their salmonella testing records, and test protein ingredients such as soya if you mix at home. Store feed dry and enclosed. Avoid ingredients grown on other pig farms.
Wildlife & other animals
Birds, foxes and badgers carry salmonella. Clear spilled feed, clutter and pooled water, and remove dead pigs promptly. Keep cattle, calves and pets away from pigs and their feed.
People & equipment
Visitors by appointment only, with farm boots and clothing and a visitors book. Clean and disinfect vehicles and equipment that have been on other livestock farms. Provide handwashing.
Outdoor units
Salmonella builds up in soil and wallows. Move the site as often as practical, rest and cultivate paddocks, keep sows per paddock low, and use bird-proof feeders.
Extra measures to discuss with your vet
- Vaccination – available for some types of salmonella.
- Feed form – coarser grinding, meal rather than pellets, and more barley and less wheat may help.
- Fermented liquid feed reduces salmonella, especially with dairy products.
- Acidifying feed or water can help in some cases.
See also our Biosecurity page, and the cleaning advice on the Pleurisy page.
More information
- QMS Pig Standards – including Appendix 2, the Scottish Pig Health Scheme
- APHA: Control of Salmonella Typhimurium in pig herds – full guidance
- About Wholesome Pigs and Scottish Pigs
The description of the Scottish Salmonella Scheme is based on the Quality Meat Scotland 2023 Pigs Standards (amended July 2026), page 4, Standard 2.11 and Appendix 2. “Why salmonella matters” and “Controlling salmonella on farm” contain public sector information from the Defra/APHA guidance Control of Salmonella typhimurium in pig herds (March 2020), © Crown copyright, licensed under the Open Government Licence v3.0.