Salmonella Dublin patients in Denmark and their distance to cattle farms

Abstract

Background: The Salmonella serotype Dublin is specifically adapted to cattle but may infect humans leading to severe disease. We described human S. Dublin cases and investigated a potential spatial relation between their addresses and cattle farms in Denmark.

Methods: We extracted S. Dublin patient surveillance data, 2000–2014, and performed descriptive analyses. We geocoded residential and cattle farm addresses and mapped their incidence by region, province and municipality. We used linear correlation and spatial autocorrelation analysis at the municipality level and calculated the direct network distance from the nearest farm to the residential address of cases and 20,000 randomly selected citizens representing the background population.

Results: We identified 484 S. Dublin cases, 57% were male, median age 65 years. Seven patients (1%) acquired their infection abroad. The 30 days all-cause mortality was 13%. Overall, cumulative incidence was 8.0 per 100,000 inhabitants. Cattle farms were located predominantly in the western part of the country. Neither visual inspection nor correlation analysis indicated a relationship between municipalities with high incidences of human cases and cattle farms. Global Moran’s Index analysis showed municipalities with high incidence of cases to be randomly distributed. We found equal direct network distances between cattle farms and both addresses of S. Dublin cases and the background population.

Conclusions: We found S. Dublin infections in Denmark to affect the elderly, be serious and acquired domestically. Our findings indicate that the risk of infection with S. Dublin in Denmark is independent of living in the proximity to cattle farms.

Keywords:

• As listed in Medical Subject Headings (MeSH)
• Salmonella
• foodborne diseases
• addresses
• spatial analysis
• geographic information systems
• mortality

Acknowledgements

The authors wish to thank Alicia Barrasa, Jens Nielsen, Hanne-Dorthe Emborg and René Bødker for their valuable comments on the manuscript. We thank all clinical microbiological laboratories in Denmark for sending in data. The fellowship of Silvia Funke was funded by the European Programme for Intervention Epidemiology Training, European Centre for Disease Prevention and Control.

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.