Drastic decrease of Salmonella Enteritidis isolated from humans in Belgium in 2005, shift in phage types and influence on foodborne outbreaks

Abstract

In Belgium, non-typhoidal salmonellosis and campylobacteriosis are the two most frequently reported foodborne illnesses. During 2005, a 71% decrease of Salmonella Enteritidis infections compared with the average annual number cases in the period 2000-2004 was recorded by the Belgian National Reference Centre for Salmonella and Shigella. After the peak of 1999, the total number of salmonellosis cases decreased gradually, with the exception of 2003 when an increase was again recorded due to the rise of isolates belonging to the serotype Enteritidis. PT4, the predominant phage type of serotype Enteriditis over recent years (except in 2003), became the second most prevalent phage type in 2005 after PT21. We present in this paper the epidemiology (incidence and trends) of human salmonellosis in Belgium and assess the role of the vaccination programme in layer flocks on the decline of the incidence of human salmonellosis and foodborne outbreaks due to S. Enteritidis.

Fig. 1

The Federal State of Belgium, the Communities, and the Regions [Source: Belgian Federal Portal: (http://www.belgium.be/eportal/application?languageParameter=en&pageid=contentPage&docId=8011).]

Fig. 2

Trend of the human Salmonella isolates, and of the two major serotypes Enteritidis and Typhimurium over the last 34 years in Belgium; number of laboratory-confirmed cases.

Fig. 3

Seasonal distribution of S. Enteritidis for the period 2000–2005.

Fig. 4

Percentages of the reported foodborne outbreaks due to Samonella spp. and S. Enteritidis in Belgium over the period 1999–2005. □, Percentage of FBO with Salmonella spp. as aetiological agent; ■, Percentage of FBO with Salmonella Enteritidis as aetiological agent (no data available for the FBO with S. Enteritidis as aetiological agent in 1999).

Fig. 5

S. Enteritidis: distribution of the most important phage types in 2000 (n=376), 2001 (n=488), 2002 (n=495), 2003 (n=492), 2004 (n=479), and 2005 (n=474).