Employing source attribution and molecular epidemiology to measure the impact of interventions on human campylobacteriosis in Scotland
Campylobacter is the most common form of foodborne illness in Scotland (a situation which is similar to the UK and most of the developed world). This study was commissioned to improve our understanding of the sources of campylobacter infection in humans in the Scottish population.
From April 2012 until March 2015, campylobacter isolates were collected from all clinical cases and from a range of host reservoirs in Grampian: chicken, turkey, cattle, sheep, pig and wild birds. The campylobacter isolates were sequence typed to identify the strain types and modelling was employed to attribute the strains to specific host reservoirs.
Source-attribution modelling revealed that chicken is the largest source for human infection at 55% to 75%, followed by 10% to 22% for sheep, 10% for cattle, 0% to 8% for pigs and 4% to 8% for wild birds. Cases reporting contact with animals prior to their illness and cases with a private water supply were more likely to have infection attributable to a non-chicken host reservoir. 19% of cases reported being abroad prior to their illness.
This study has provided an insight into the dynamic nature of campylobacter and provides key data on prevalence and strain types in the main food vehicles and animal reservoirs. It provides evidence that chicken continues to be the most important source of human infection, most likely through the consumption of undercooked chicken or through cross-contamination in the kitchen.