Using Outbreak Data for Source Attribution of Human Salmonellosis and Campylobacteriosis in Europe

Abstract

Salmonella and Campylobacter are the most important bacterial causes of foodborne illness in Europe. To identify and prioritize food safety interventions, it is important to quantify the burden of human foodborne illness attributable to specific sources. Data from outbreak investigations are observed at the public health endpoint and can therefore be a direct measure of attribution at the point of exposure. An analysis or summary of outbreak investigations is useful for attributing illnesses to foods, but often the implicated foods in reported outbreaks are complex foods, containing several food items, many of which could be the specific source of the infection. We describe a method that is able to attribute human cases to specific food items contained in complex foods. The model is based on data from investigations of Salmonella and Campylobacter outbreaks in the European Union in 2005 and 2006. The reporting of the causative vehicles for the outbreaks was not harmonized between and within countries. Consequently, we organized the implicated foods in mutually exclusive food categories. We estimated that the most important food sources for salmonellosis cases were eggs (32%) and meat and poultry-meat (15%), and that the majority of the cases of campylobacteriosis were attributed to chicken (10%). For both pathogens, a large proportion of cases could not be linked to any source. Among illnesses that could be attributed to a source, 58% of salmonellosis cases were attributed to eggs, and 29% of campylobacteriosis cases were attributed to chicken. Results also revealed regional differences in the relative importance of specific sources. We assessed the method to be of limited value to attribute human campylobacteriosis due to the limited number of outbreaks. Nevertheless, the presented source attribution approach can be applied to other foodborne pathogens, and is easily adaptable to countries having an appropriate number of reported outbreaks.

Scientific Opinion on the public health risks of table eggs due to deterioration and development of pathogens

“…In the EFSA Scientific Opinion on Quantification of the risk posed by broiler meat to human campylobacteriosis in the EU (EFSA BIOHAZ Panel, 2010c), 1.3 % of Campylobacter outbreaks were attributed to eggs, through source attribution based on outbreak investigation data. However, Pires et al (2010) questioned the reliability of using outbreak data for source attribution for Campylobacter, because the relative contribution of sources to sporadic and outbreak associated disease appears to differ, which could bias estimates based only on outbreak data.…”

Scientific Opinion on the development of a risk ranking framework on biological hazards

“…Methods for source attribution of foodborne diseases include e.g. use of microbial subtyping (Hald et al, 2007;Little et al, 2010;Mullner et al, 2009a), comparative exposure assessment (Evers et al, 2008;FDA, 2003), analysis of foodborne disease outbreak data (Pires et al, 2010a;Pires et al, 2012) and systematic review of case-control investigations of sporadic illness (Domingues et al, 2012) (Domingues et al, 2011). However, for many pathogens sufficient data for source attribution are missing.…”

Detection of Salmonella human carriers in Colombian outbreak areas

“…Furthermore, the Salmonella serotype determines its ability to cause disease, as well as clinical symptoms and outbreak outcomes [4][5][6]. Animal and human reservoirs are responsible for the circulation of the microorganism, contributing to the occurrence of sporadic cases and outbreaks [7][8][9][10]. In addition, some food sources have higher impact on public health than do others [11][12][13][14].…”

“…Nevertheless, the impact of these interventions is not conclusive, a fact reflected by the variability of surveillance programs for different infective sources [7]. Several mathematic and statistical approaches, such as a Bayesian model, have been developed to quantify the contributions of each major animal-food sources to human salmonellosis [15,16].…”