Dutch Salmonella cases hit record low

Since the beginning of the century, the number of patients with salmonellosis has more than halved, according to a Dutch epidemiological report.

There were an estimated 27,440 patients with acute gastroenteritis due to salmonellosis in 2017 which means that the Netherlands has one of the lowest incident rates in Europe. Reasons for this include the effect of control programs for farm animals and improvements in the hygiene of the food production process.

The main source of infections in humans is pork (28 percent) with table eggs in second place (15 percent), followed by chicken (13 percent) and 2 percent from beef.

The National Institute for Public Health and the Environment (RIVM) conducts laboratory surveillance on salmonellosis in the Netherlands. Fifteen regional public health labs form the surveillance network for gastroenteric pathogens which covers 64 percent of the Dutch population.

As a National Reference Center for Salmonella, RIVM receives isolates for serotyping. They come from different monitoring programs on farms, slaughterhouses, and supermarkets including those by the Dutch Food and Consumer Product Safety Authority (NVWA).

In 2017, the 968 Salmonella isolates from patients in the Netherlands was lower than in 2016 (1,159) and comparable with 2014 (986) and 2015 (979). A total of 12 percent were travel-related. The most common serotypes were Enteritidis, Typhimurium-monophasic 1,4,5,12:i:- and Typhimurium. Adjusting for the coverage ratio makes 1,513 isolates nationwide.

Outbreaks last year included 14 residents of a nursing home infected by the ciprofloxacin-resistant serotype Salmonella Kentucky and 21 young adults struck down with monophasic Salmonella typhimurium linked to contaminated junk food. No source could be found for smaller outbreaks of Salmonella Infantis with 14 cases, Salmonella Agbeni with 10 infections and Salmonella Newport with eight ill.

The actual number of individuals with salmonellosis is estimated to be more than 15 times as high as the figure of lab-diagnosed patients.

The 2016 rise was mainly caused by an international outbreak of Salmonella enteritidis traced to Polish eggs with 202 patients in 2016 and 35 in 2017 and a smaller outbreak with 53 cases that started in 2016 and continued until March 2017 in the Netherlands and Belgium caused by Salmonella bovismorbificans in raw ham from Belgium.

Epidemiological studies have made it possible to estimate, on the basis of lab findings, how many people in the general population get acute gastroenteritis by Salmonella, go to the GP, end up in the hospital and die.

For 2015-2017, the number of patients with acute gastroenteritis due to Salmonella infections was estimated to be more than 27,000. This corresponds to about 1,200 Disability Adjusted Life Years (DALY) and the Cost of Illness (COI) comes to €19 million ($22 million). The DALYs and COI were higher in 2016 but this can be attributed to the two large outbreaks referenced above.

For Campylobacter the number of patients with acute gastroenteritis, DALY and COI are about three times as high compared to Salmonella. For Salmonella infections, it is estimated that about 80 percent comes from food while for Campylobacter this figure is around one third.

Development of antibiotic resistance remains a source of concern, in particular, multidrug resistance and Extended-Spectrum Beta-Lactamase (ESBL) production in different serotypes and the increase in Salmonella strains resistant to fluoroquinolones.

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