Salmonella and the chicken: reflections on salmonellosis and its control in the United Kingdom

Abstract

AbstractThe association between Salmonella with chicken meat and eggs is the best-known source of a foodborne infection and its livestock reservoir. Whilst expansion of intensive farming and globalisation of the industry have facilitated its spread, Salmonella has an impressive toolkit that allows its colonisation and survival in the harsh environment of both the gut and egg. After infection in chickens Salmonella can pass through the pH of the stomach and, through adhesins such as fimbriae, are able to attach to the gut wall. Within the intestines, diverse metabolic pathways mean Salmonella can utilise a range of nutrients and elicit inflammation that releases oxygen to help its colonisation process through competition with the strict anaerobes in the gut. Certain Salmonella are also able to colonise the reproductive tract and pass into developing eggs in the ovary or oviduct prior to the addition of the egg-shell. Salmonella is also able to withstand high levels of antimicrobial peptides and antibody within eggs.A range of controls including vaccination, microbial-based products, coupled with improvements to hygiene and biosecurity, have all played a role in reducing Salmonella-foodborne illness associated with chicken consumption in Europe, though no single method is a ‘magic bullet’ of complete control. New variants, including antimicrobial resistant variants, such as Salmonella Typhimurium ST34 and its monophasic variants, pose a constant threat. In addition, serovars such as Salmonella Kentucky, associated with feed contamination but not protected by current vaccines, pose specific difficulties for control.A clear understanding of the infection biology of Salmonella can help underpin the development and application of controls, while areas of new understanding, such as the role and potential exploitation of the microbiome, offer up potentially novel controls. This all requires maintenance of surveillance systems and risk-based approaches to keep effective control of the Salmonella in chicken production.