Purpose: The aim of this study was to investigate risk factors associated with STEC infections in humans in New Zealand and provide epidemiological information on the source and exposure pathways.
Methods: During a national prospective case-control study from July 2011 – July 2012, any confirmed case of STEC infection reported to Public Health Units, together with a random selection of controls representative of the national demography, were interviewed for risk factor evaluation using a standardized questionnaire. Questionnaire data were analyzed using multivariable logistic regression with multiple imputations to adjust for the small proportion of missing data in some variables.
Results: Data from 113 eligible cases and 506 controls were evaluated. Animal and environmental risk factors for STEC infections that were statistically significant (P < 0.05) were: cattle livestock being present on meshblock (OR 1.89, 1.04 - 3.42 95% CI) (meshblock is smallest geographical unit statistical data are collected for), having contact with animal manure (OR 2.09, 1.12 - 3.90 95% CI), having contact with recreational waters (OR 2.95, 1.30 - 6.70 95% CI). However, food-associated risk factors were not identified as sources of STEC infection.
Significance: These findings are somewhat contrary to source attribution information from other countries, strongly indicating that environmental and animal contacts constitute much more important exposure pathways for human cases of STEC in New Zealand than food pathways.