Open Access Research article

The epidemiology of travel-related Salmonella Enteritidis in Ontario, Canada, 2010–2011

Mary-Kathryn Tighe1, Rachel Savage1, Linda Vrbova124, Miriam Toolan13, Yvonne Whitfield15, Csaba Varga56, Brenda Lee15, Vanessa Allen1, Anne Maki1, Ryan Walton127, Caitlin Johnson17, Badal Dhar1, Rafiq Ahmed9, Natasha S Crowcroft178 and Dean Middleton17*

Author Affiliations

1 Public Health Ontario, 480 University Ave, Toronto, M5G 1V2, Canada

2 Canadian Field Epidemiology Program, Public Health Agency of Canada, 8 Colonnade Road, Ottawa, Ontario, K2E 7M6, Canada

3 Guy’s, King’s and St Thomas’ School of Medicine, London, SE1 9RT, UK

4 School of Population and Public Health, University of British Columbia, 2206 East Mall, Vancouver, BC, V6T 1Z3, Canada

5 Ontario Ministry of Health and Long-Term Care, 1075 Bay St, Toronto, Ontario, M5S 2B1, Canada

6 Department of Population Medicine, University of Guelph, Guelph, Ontario, N1G 2 W1, Canada

7 Dalla Lana School of Public Health, University of Toronto, 155 College St., Health Sciences Building, 6th Floor, Toronto, Ontario, M5T 3 M7, Canada

8 Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada

9 National Microbiology Laboratory, Public Health Agency of Canada, Ottawa, Canada

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BMC Public Health 2012, 12:310  doi:10.1186/1471-2458-12-310

Published: 26 April 2012

Abstract

Background

Increases in the number of salmonellosis cases due to Salmonella Enteritidis (SE) in 2010 and 2011 prompted a public health investigation in Ontario, Canada. In this report, we describe the current epidemiology of travel-related (TR) SE, compare demographics, symptoms and phage types (PTs) of TR and domestically-acquired (DA) cases, and estimate the odds of acquiring SE by region of the world visited.

Methods

All incident cases of culture confirmed SE in Ontario obtained from isolates and specimens submitted to public health laboratories were included in this study. Demographic and illness characteristics of TR and DA cases were compared. A national travel survey was used to provide estimates for the number of travellers to various destinations to approximate rates of SE in travellers. Multivariate logistic regression was used to estimate the odds of acquiring SE when travelling to various world regions.

Results

Overall, 51.9% of SE cases were TR during the study period. This ranged from 35.7% TR cases in the summer travel period to 65.1% TR cases in the winter travel period. Compared to DA cases, TR cases were older and were less likely to seek hospital care. For Ontario travellers, the adjusted odds of acquiring SE was the highest for the Caribbean (OR 37.29, 95% CI 17.87-77.82) when compared to Europe. Certain PTs were more commonly associated with travel (e.g., 1, 4, 5b, 7a, Atypical) than with domestic infection. Of the TR cases, 88.9% were associated with travel to the Caribbean and Mexico region, of whom 90.1% reported staying on a resort. Within this region, there were distinct associations between PTs and countries.

Conclusions

There is a large burden of TR illness from SE in Ontario. Accurate classification of cases by travel history is important to better understand the source of infections. The findings emphasize the need to make travellers, especially to the Caribbean, and health professionals who provide advice to travellers, aware of this risk. The findings may be generalized to other jurisdictions with travel behaviours in their residents similar to Ontario residents.