The causes of the simultaneous rise of salmonellosis morbidity induced by S. enteritidis among the population of three towns in the Perm region were studied. The study revealed the leading role of eggs and chicken meat as factors contributing to the transfer of this infection to the population of different territories, commonly supplied with the products of one poultry plant. The contamination of eggs and chickens with S. enteritidis occurred at the plant due to Salmonella infection of chickens, parallel with the use of nonbalanced mixed fodder, originally intended for feeding swine. Analysis of the epidemic and epizootic processes of Salmonella infection in this epidemic situation made it possible to reliably establish the factors contributing to the transfer of the infective agent and the site of contamination.
In order to determine the extent and infectious vehicle of an outbreak of Salmonella enteritidis phage type 6 at the New Year celebration of the Copenhagen Medical Association on 15 January 1999, a cohort study including 77 guests (90% of the participants) and 11 staff was carried out. There was little variation in the degree of exposure among the guests, meaning that identification of the probable infectious vehicle was not possible here. However, among the staff, intake of minced raw salmon was associated with increased risk of disease. Uncooked eggs were used in the preparation of this dish and since S. enteritidis phage type 6 is in Denmark almost exclusively found among egg-laying hens, these findings led to the conclusion that the outbreak was most likely caused by the use of raw eggs. The importance of notification of suspected foodborne disease and microbiological examination of people thereby exposed is stressed.
Mathematical models that estimate the proportion of foodborne illnesses attributable to food commodities at specific points in the food chain may be useful to risk managers and policy makers to formulate public health goals, prioritize interventions, and document the effectiveness of mitigations aimed at reducing illness. Using human surveillance data on laboratory-confirmed Salmonella infections from the Centers for Disease Control and Prevention and Salmonella testing data from U.S. Department of Agriculture Food Safety and Inspection Service's regulatory programs, we developed a point-of-processing foodborne illness attribution model by adapting the Hald Salmonella Bayesian source attribution model. Key model outputs include estimates of the relative proportions of domestically acquired sporadic human Salmonella infections resulting from contamination of raw meat, poultry, and egg products processed in the United States from 1998 through 2003. The current model estimates the relative contribution of chicken (48%), ground beef (28%), turkey (17%), egg products (6%), intact beef (1%), and pork (
Based on the Danish Salmonella surveillance in 2000-2001, we developed a mathematical model for quantifying the contribution of each major animal-food sources to human salmonellosis caused by antimicrobial resistant bacteria. Domestic food products accounted for 53.1% of all cases, mainly caused by table eggs (37.6%). A large proportion (19%) of cases were travel related, while 18% could not be associated with any source. Imported food products accounted for 9.5% of all cases; the most important source being imported chicken. Multidrug and quinolone resistance was rarely found in cases acquired from Danish food, but was common in cases related to imported products (49.7% and 35.6% of attributable cases) and travelling (26.5% and 38.3% of attributable cases). For most serovars, the quinolone-resistant isolates were found to be associated with relatively more human infections than that of resistant isolates, which in turn was higher than that of susceptible isolates. This may be due to quinolone-resistant isolates having a higher ability to survive food processing and/or cause disease. This study showed domestic food to be the most important source of Salmonella infections in Denmark, but infections with multidrug- and quinolone-resistant isolates were more commonly caused by imported food products and travelling, emphasizing the need for a global perspective on food safety and antimicrobial usage.
Based on the data from the integrated Danish Salmonella surveillance in 1999, we developed a mathematical model for quantifying the contribution of each of the major animal-food sources to human salmonellosis. The model was set up to calculate the number of domestic and sporadic cases caused by different Salmonella sero and phage types as a function of the prevalence of these Salmonella types in the animal-food sources and the amount of food source consumed. A multiparameter prior accounting for the presumed but unknown differences between serotypes and food sources with respect to causing human salmonellosis was also included. The joint posterior distribution was estimated by fitting the model to the reported number of domestic and sporadic cases per Salmonella type in a Bayesian framework using Markov Chain Monte Carlo simulation. The number of domestic and sporadic cases was obtained by subtracting the estimated number of travel- and outbreak-associated cases from the total number of reported cases, i.e., the observed data. The most important food sources were found to be table eggs and domestically produced pork comprising 47.1% (95% credibility interval, CI: 43.3-50.8%) and 9% (95% CI: 7.8-10.4%) of the cases, respectively. Taken together, imported foods were estimated to account for 11.8% (95% CI: 5.0-19.0%) of the cases. Other food sources considered had only a minor impact, whereas 25% of the cases could not be associated with any source. This approach of quantifying the contribution of the various sources to human salmonellosis has proved to be a valuable tool in risk management in Denmark and provides an example of how to integrate quantitative risk assessment and zoonotic disease surveillance.
Data from population-based studies and national surveillance systems were collated and analyzed to estimate the impact of disease and risks associated with eating different foods in England and Wales. From 1996 to 2000, an estimated 1,724,315 cases of indigenous foodborne disease per year resulted in 21,997 hospitalizations and 687 deaths. The greatest impact on the healthcare sector arose from foodborne Campylobacter infection (160,788 primary care visits and 15,918 hospitalizations), while salmonellosis caused the most deaths (209). The most important cause of indigenous foodborne disease was contaminated chicken (398,420 cases, risk [cases/million servings] = 111; case-fatality rate [deaths/100,000 cases] = 35, deaths = 141). Red meat (beef, lamb, and pork) contributed heavily to deaths, despite lower levels of risk (287,485 cases, risk = 24, case-fatality rate = 57, deaths = 164). Reducing the impact of indigenous foodborne disease is mainly dependent on controlling the contamination of chicken.
Cites: Int J Food Microbiol. 1997 Apr 15;35(3):195-2049105928
A public plan for eradicating Salmonella in Danish table-egg production was implemented in 1996. During 2002, the poultry industry took over the responsibility of the programme. The proportion of infected layer flocks was reduced from 13.4% in 1998 to 0.4% in 2006. The public-health impact of the plan has been quite marked. In 1997, 55-65% of the 5015 cases of human salmonellosis were estimated to be associated with eggs. In 2006, these figures were reduced to 1658 and 5-7%, respectively. Based on an assessment of the number of human cases attributable to table eggs, we used probabilistic modelling to estimate the avoided societal costs (health care and lost labour), and compared these with the public costs of control. The probable avoided societal costs during 1998-2002 were estimated to be 23.3 million euros (95% CI 16.3-34.9), and the results showed a continuous decreasing cost-benefit ratio reaching well below 1 in 2002. Further reductions in the primary production based on effective surveillance and control are required to ensure continued success.
To estimate the consumer risk of contracting Salmonella infection via shell eggs and to evaluate the effect of possible preventative measures, quantitative microbiological risk assessment is being developed in Finland. As a part of the risk assessment, a survey of 918 respondents was conducted to study how households purchase, store, handle, and use eggs. In addition, suitability of the Internet as a survey method was compared with a postal survey. Shell eggs were usually purchased once every 2 weeks (41% of all the respondents). Ninety-one percent of the respondents bought eggs in groceries and 93% stored eggs at chilled temperatures. The majority of the respondents (80%) only had eggs in their home for which the best-before date had not expired. Only 34% of the respondents said that they always washed their hands after breaking eggs. Consumption of well-cooked eggs accounted for 84%, consumption of soft-boiled eggs for 12%, and consumption of raw eggs for 4% of the total amount of eggs consumed. The elderly used eggs more frequently than the whole population, but the consumption of raw egg dishes decreased with age. The Internet survey was a rapid method for transmitting information, but its response rate was low (9%), and it did not appear to be a suitable tool for data collection in a general population. The results indicate that although the majority of the respondents had safe egg-handling practices, a substantial minority of the consumers had risk-prone behavior.
A rise in morbidity caused by S. enteritidis at individual territories of the Russian Federation in the second half of 1980s was due to the consumption of insufficiently heated infected chicken eggs and the nonobservance of sanitary and hygienic rules in the preparation of food from chicken meat. The spread of S. enteritidis in the Russian Federation occurred mainly at the territories supplied with incubator eggs from the same poultry-breeding enterprise. S. enteritidis strains isolated from infected patients, chicken eggs, follicles and chicken-meat products belonged to biovar Jena (as a rule, to phagovar 1), had plasmid with a mol. wt. of 38 MD, produced no aerobactin, and their overwhelming majority was resistant to antibiotics.
A case-control study was conducted from 1 January to 31 May 2003 to identify risk factors for S . Heidelberg infection in Canada. Controls were pair-matched by age group and telephone exchange to 95 cases. Exposures in the 7 days before illness/interview were assessed using multivariate conditional logistic regression. Consumption of home-prepared chicken nuggets and/or strips [matched odds ratio (mOR) 4.0, 95% confidence interval (CI) 1.4-13.8], and undercooked eggs (mOR 7.5, 95% CI 1.5-75.5) increased the risk of illness. Exposure to a farm setting lowered the risk (mOR 0.22, 95% CI 0.03-1.00). The population-attributable fraction associated with chicken nuggets/strips was 34% and with undercooked eggs was 16%. One-third of study participants did not perceive, handle or prepare chicken nuggets and strips as high-risk products, although the majority of the products on the Canadian market are raw. These findings have prompted changes in product-labelling policy and consumer education.