Health agency reports Salmonella at highest level since 2008 in Ireland

Ireland has reported the highest number of salmonellosis cases since 2008, according to the country’s annual epidemiological report.

There were 414 cases notified in 2017 – 378 confirmed and 36 probable infections. It represents a 37 percent increase compared to 2016. International travel is a large contributor to the burden of salmonellosis in Ireland, particularly in summer months.

The rise was mostly because of one large outbreak of Salmonella Brandenburg, with 71 cases. However, overall incidence of salmonellosis in Ireland remains low compared to other parts of Europe, according to the Health Protection Surveillance Centre (HPSC).

Similar to 2016, the highest age-specific incidence rate was in children under five years old. This is likely influenced by clinicians seeking samples in that age group. The lowest age specific rate was in the five to nine year old age group. Overall burden of disease acquired in Ireland is disproportionally associated with children under 15 years and adults over 65 years.

Patients were sick from one to 35 days, for a median duration of illness of seven days, based on observations for 190 cases. A total of 35 percent, or 124 out of 357, were hospitalized.

Where country of infection was reported, 139 of 348 cases were travel-associated. These cases peaked between July and September coinciding with the summer holiday period. Distribution of non-travel-associated cases was affected by one large outbreak from May to June. Most common countries of infection were Spain with 38, Thailand with 11, Vietnam with 10, and Portugal with 10.

Four outbreaks of salmonellosis were reported in 2017. The largest led to five people being hospitalized and one death, with an inquest pending. A total of 35 confirmed and 37 probable cases of Salmonella Brandenburg were linked to several parties which had buffet food from the same catering operation.

A small Salmonella Enteritidis outbreak of two cases was associated with a restaurant.

One Salmonella Newport and one monophasic Typhimurium outbreak were identified at the National Salmonella, Shigella and Listeria Reference Laboratory (NSSLRL) due to clustering by whole genome sequencing (WGS) and were associated with travel to Spain. Cases were linked by geographic location but did not report common exposures such as the same accommodation or restaurants and causes of the outbreaks were not established.

A cluster of four Salmonella Enteritidis cases were identified by WGS as linked to a wider salmonellosis outbreak in Europe associated with Polish eggs. Almost 1,500 people have been sickened in the outbreak that has lasted more than six years and affected 18 countries. The last reported case in Scotland was September 2018.

Cases who acquired disease in Ireland or other parts of Europe were younger than those who became ill following long-haul travel. Disease acquired in the country was more commonly caused by Salmonella Typhimurium and monophasic Typhimurium strains at 35 percent, with Salmonella Enteritis strains responsible in 9 percent. Other strains made up the remaining 52 percent.

However, disease acquired in Europe was most commonly associated with Salmonella Enteritidis  at 48 percent, followed by other strains at 28 percent, and Salmonella Typhimurium and monophasic Typhimurium strains accounting for 24 percent of cases.

For cases associated with illness in the rest of the world, non-Enteritis, non-Typhimurium cases predominated with 55 percent, with Salmonella Enteritidis and Salmonella Typhimurium including monophasic Typhimurium strains each accounting for 23 percent.

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