No 13 - 2012

Zoonotic intestinal infections 2011

Zoonoses are diseases that are transferred from animals to humans. Zoonotic intestinal infections arise after ingestion of contaminated foods or water, or after contact with infected animals or humans. Bacterial entero-pathogens are monitored through the laboratory surveillance system.

Furthermore, verocytotoxin-producing E. coli (VTEC) infections and cases of haemolytic uraemic syndrome (HUS) are clinically notifiable on Form 1515, as are intestinal infections (regardless of aetiology) in cases with suspicion of infection from a specific food or water source.

General development

The number of salmonella cases decreased from 1,600 cases in 2010 to 1,167 in 2011 (21 per 105), Figure 1.

S. Enteritidis and S. Typhimurium were the most frequently occurring serotypes, Table 1.

Compared with 2010, the number of cases with these two serotypes decreased by 24% and 53%, respectively. The group ‘Other serotypes’, comprising a total of 691 cases, decreased by 9%. This latter group represented 99 different serotypes. Monophasic Typhimurium comprises isolates with the antigen formula 1,4,[5],12:i:-.

In 2011, a total of 4,068 (73 per 105) Campylobacter jejuni/coli infections were reported; nearly as many as the preceding year, Figure 1.
A total of 224 Yersinia enterocolitica cases (4.0 per 105) were recorded, 16% up from 2010, Figure 1.

In all, 224 VTEC cases (4.0 per 10⁵) were recorded, 21% up from the previous year. Hereof 169 and 215 cases, respectively, were notified via the clinical and laboratory-based notification systems. Isolates were available for 207 VTEC cases; the two most frequently occurring serogroups were O157 and O104, with 27 (13%) and 25 (12%) cases, respectively.
A total of 13 HUS cases were notified, including ten confirmed as VTEC. The age-specific incidence is presented in Table 2.

Further information: ssi.dk/data (Danish language).

Infections acquired abroad

The SSI collected travel information via telephone interviews with all salmonella and campylobacter patients reported via departments of clinical microbiology in Odense and Aalborg. The patients were asked about the date of disease onset and whether they had travelled abroad within a seven-day period prior to disease onset.

Information was obtained from a total of 79% of the salmonella and 74% of the campylobacter cases. Among these, 32% of campylobacter infections had been acquired abroad, while the corresponding figure for S. Enteritidis was 71%, S. Typhimurium 20%, the monophasic S. Typhimurium 35% and the group or other salmonella serotypes 49%. For salmonella, the country in which most persons were infected was Thailand, followed by Turkey and Egypt.

For campylobacter, it was Turkey followed by Spain and Thailand.

Commentary

In 2011, the number of salmonella cases continued to follow a decreasing trend, and incidence is now at par with that of the early 1980s before the general salmonella epidemics started. About half of the cases were acquired during travels abroad, and in 2011 only two nation-wide salmonella outbreaks were observed. An S. Typhimurium outbreak was caused by smoked pork tenderloin, while an S. Strachcona outbreak was due to imported tomatoes, EPI-NEWS 4/12.

In contrast, the number of campylobacter infections remained high and these now occur nearly three times as frequently as salmonella. The primary source of infection is poultry and nearly one third is infected abroad.

2011 saw more cases of VTEC and VTEC caused by HUS than previously, primarily in association with the very large outbreak in North Germany in spring of 2011. Subsequently, it was demonstrated that this VTEC O104 outbreak was caused by intake of fresh fenugreek sprouts from a single German producer, EPI-NEWS 27-33/11.

(S. Ethelberg, K. Mølbak, Department of Infectious Disease Epidemiology, K.E.P. Olsen, F. Scheutz, E.M. Nielsen, DBMP) 

28 March 2012