Incidence of zoonotic Salmonella species bacteraemia: a multi-national population-based study

Objectives: Although zoonotic (non-typhoidal) Salmonella species are important causes of invasive infections worldwide, few studies have investigated their epidemiology at the population level. The objective of this study was to define the incidence of zoonotic Salmonella species bacteraemia in a large multi-national population and to evaluate temporal and regional differences.
Methods: Population-based laboratory surveillance for all zoonotic Salmonella species bacteraemias was conducted in five regions (Finland, Canberra, Australia, North Jutland Region, Denmark, and Calgary and Sherbrooke, Canada; combined population 7.5 million residents annually) during 2000-2007.
Results: A total of 480 zoonotic Salmonella species bacteraemias were identified for an overall annual incidence of 8.1 per million population. The incidence was lowest in the spring and highest in the summer, and progressively increased during the eight years of the study with a doubling of the rate from 6.1 per million in 2000 to 12.2 per million in 2007. Overall the acquisition risk increased with advancing age and males were at significantly higher risk as compared to females (10.2 vs. 6.2/million; relative risk 1.7; 95% confidence interval 1.4-2.0). The occurrence varied significantly among the five study regions with annual incidence rates per million population of 22.2 in Sherbrooke, 18.7 in North Jutland Region, 7.5 in Finland, 6.1 in Calgary, and 4.2 in Canberra.
Conclusions: Zoonotic Salmonella species bacteraemias are increasing. The determinants of increased risk among males, older individuals, and between regions merit further investigation.