A new scientific study has highlighted the success of attempts to reduce salmonella infection in the United Kingdom.
A team led by by an epidemiologist at Public Health England has reviewed the emergence of salmonella enteritidis in the UK, describing it as the “largest and most persistent epidemic of foodborne infection attributable to a single subtype of any pathogen since systematic national microbiological surveillance was established.” The team also examined attempts to tackle the epidemic - and it highlighted figures that show, whilst salmonella remains a problem in many parts of Europe and the United States, incidence of the bacteria has been almost eradicated in the UK.
“Surveillance data demonstrate that the rates of human S. enterica ser. Enteritidis infection in England and Wales remained high during 1988–1998 despite national guidance aimed at the public and industry (20). From 1997 to 2011, disease incidence decreased 99 per cent,” said the report. The researchers said the decline in salmonella coincided with the introduction of vaccination by the UK egg industry. “The reporting of egg-associated outbreaks did not start to decline until 1997, after the introduction of S. enterica ser. Enteritidis vaccination and flock hygiene program aimed at laying chicken flocks.”
The research has been hailed by the British Egg Industry Council as “further endorsement of the British egg industry’s success in tackling salmonella.” BEIC issued a statement, saying, “The paper cites a 99 per cent decrease in human cases of salmonella enteritidis between 1997 and 2011, following the introduction of the Lion scheme. It highlights ‘the improvements in hygienic practice from egg production and distribution through the major supermarket chains has resulted in major improvements in the microbiological quality of eggs bought by consumers in the United Kingdom’.” The statement also pointed to the researchers’ conclusion that salmonella was still a problem in many other countries in Europe.
“Despite the spectacular results in the British industry, the paper highlights that salmonella contamination of eggs remains a problem in many EU member states and warns that ‘investigation of outbreaks indicates that the infection is mainly transmitted through the consumption of imported eggs in commercial catering’. It recommends the need to incorporate safer practices across the catering sector, as the use of imported raw shell eggs and poor hygiene practices are more common in this area. The report concludes that the introduction of effective interventions, including the British Lion scheme, may have reduced the number of salmonella outbreaks by almost 1m, reducing the number of illness by more than 6m and the number of deaths caused by salmonella by 2,000.”
The study was led by Christopher R. Lane, an epidemiologist at Public Health England in London. He works in gastrointestinal disease surveillance, mainly focusing on the epidemiology of salmonellosis, and his research team set out to review 67 years of surveillance data to examine the features, underlying causes, and overall effects of enteritidis.
The report said, “In England and Wales, the emergence of Salmonella enterica serovar Enteritidis resulted in the largest and most persistent epidemic of foodborne infection attributable to a single subtype of any pathogen since systematic national microbiological surveillance was established. We reviewed 67 years of surveillance data to examine the features, underlying causes, and overall effects of S. enterica ser. Enteritidis. The epidemic was associated with the consumption of contaminated chicken meat and eggs, and a decline in the number of infections began after the adoption of vaccination and other measures in production and distribution of chicken meat and eggs. We estimate that >525,000 persons became ill during the course of the epidemic, which caused a total of 6,750,000 days of illness, 27,000 hospitalisations, and 2,000 deaths. Measures undertaken to control the epidemic have resulted in a major reduction in foodborne disease in England and Wales.”
Mr Lane said that the decline in outbreaks associated with eggs started following the introduction of vaccination and other hygiene measures into the UK layer flock. These measures included improved rodent control, feed monitoring, biohazard control, microbiological monitoring throughout all stages of production and industry quality assurance schemes. “This point also marks the start of the sharp decline in the human S. enterica ser. Enteritidis epidemic.”
He said that consideration of trends in the human and veterinary surveillance data and the findings of a 1988 case–control study showed that the salmonella epidemic in humans was associated with the consumption of both chicken and eggs. “However, because control of S.
enterica ser. Enteritidis in the production of chicken meat had much less effect on the course of the epidemic than control in eggs, we further conclude that the epidemic was largely attributable to the contamination of eggs. Persons became infected through the consumption of contaminated foods in commercial catering and home settings. The improvements in hygienic practice from egg production and distribution through the main supermarket chains has resulted in major improvements in the microbiologic quality of eggs bought by consumers in the United Kingdom.”
He said that the introduction of controls in the United States and Denmark had also had some success, but surveillance of layer flocks in Europe indicated that enteritidis infection remained a problem in egg production in many European Union member states. “International surveillance data and recently reported outbreaks also demonstrate that contamination of eggs remains a problem in many parts of Europe and the United States. This knowledge adds weight to our conclusion that the reduction in S. enterica ser. Enteritidis in chicken flocks in Great Britain stemmed from the introduction and maintenance of a suite of carefully designed and regulated interventions.”
He said there was evidence that “cross-sectoral national control strategies designed according to national needs and conditions” could be extremely effective in reducing the risk to human populations worldwide.
