Understanding how salmonella bacteria colonises farm animals and causes disease.

Background

Salmonella is a harmful bacterium of global importance that affects both animal and human health. In farmed animals, it can cause serious disease, while in people it is a common cause of foodborne illness.

Salmonella can spread from livestock through the farm environment and along the food chain to humans. Infection in people typically leads to diarrhoeal disease, which can be severe in vulnerable groups such as young children, the elderly, and those with weakened immune systems.

Each year, salmonella is estimated to infect tens of millions of people worldwide and cause thousands of deaths, highlighting its major public health impact.

In livestock, salmonella infections can result in:

• diarrhoea
• abortion
• typhoid-like systemic disease.

These outcomes affect animal welfare and can also lead to significant economic losses for farmers.

Vaccination and improved biosecurity have helped reduce salmonella contamination in poultry meat and eggs. However, there is a need for stronger control measures in livestock, where the bacterium continues to circulate and poses risks to both animal health and food safety.

Strengthening prevention and control at the farm level is a key step toward protecting the entire food chain and reducing human illness.

At LARIF

The Large Animal Research and Imaging Facility (LARIF) provides specialist facilities to safely study infectious diseases in livestock. Researchers can inoculate cattle, pigs, and chickens with salmonella and other hazard category 2 pathogens, including genetically modified strains, under carefully controlled conditions.

LARIF supports a range of collaborative projects with industry and academic partners. Recent examples include:

• work with Hy-Line to analyse the genetic basis of resistance to fowl typhoid
• research with Zoetis on how host and bacterial factors influence bovine salmonellosis.

These partnerships help translate scientific discoveries into practical solutions for animal health and food safety.

Professor Mark Stevens of the Roslin Institute is part of a consortium led by the London School of Hygiene and Tropical Medicine that secured £5.7 million in funding from the Biotechnology and Biological Sciences Research Council (BBSRC). The goal is to develop vaccines targeting avian and zoonotic pathogens.

His poultry research is strengthened by the expertise and resources of the National Avian Research Facility on the Easter Bush campus. This includes access to unique chicken lines, advanced immunological tools, and capabilities for genome modification.

Impact

Research led by Professor Mark Stevens has generated important insights into how salmonella colonises the intestines of farm animals and causes disease.

The team uses innovative, sequencing-based technologies to study the roles of thousands of salmonella genes during infection. These approaches allow scientists to:

• identify which genes are essential for infection
• assess the potential risk posed by different salmonella strains
• gain detailed insights while using minimal numbers of animals

The Stevens laboratory also uses carefully designed surgical models to examine how salmonella triggers gastroenteritis and moves beyond the gut to infect other parts of the body. This work helps reveal the step-by-step processes behind disease development.

The laboratory’s surgical and genetic methods significantly reduce the number of animals needed to study bacterial disease. This commitment to more ethical and efficient research has been recognised with an international award for advancing the 3Rs - replacement, reduction, and refinement - in the development of veterinary medicines.

Publications