A Danish study has looked at sources of Campylobacter infection to help improve national prevention guidelines.

Researchers from the Statens Serum Institut (SSI) and University of Copenhagen led a case-control study among Danes aged one to 30 years from January to December 2016. People in this age bracket are believed to be at the highest risk of disease.

Campylobacteriosis is the most common bacterial gastrointestinal infection in Denmark with more than 4,000 cases reported each year and an increasing trend since 2012.

Participants were invited by letter to complete an online questionnaire. The study recruited 1,366 cases and 4,418 controls, of whom 887 and 2,935 respectively, completed the questionnaire and results were published in the journal Clinical Epidemiology.

A multivariate model for domestically acquired cases showed increased risk of infection with bathing in fresh water, contact to beach sand, owning a pet dog with diarrhea, and eating minced beef or chicken. The model for children highlighted similar factors and included bathing in a paddling pool and eating fresh strawberries. The risk from strawberries may be linked to hygiene practices such as not washing them as children frequently eat strawberries from the field when picking them or directly from the box at retail.

A separate analysis for those reporting foreign travel showed increased infection risk when traveling to Asia, Africa, or Turkey and that eating from street kitchens and having contact with water during traveling were also risk factors.

The study re-confirmed handling and consumption of chicken as an important risk factor while highlighting minced beef as a potential new issue. It showed that almost one third of Campylobacter cases in Denmark each year may be attributed to chicken.

Risk associated with minced beef, referred to as ground beef in the U.S., may be a recent occurrence related to the introduction of Modified Atmosphere Packaging (MAP). Minced meat in MAP has lower concentrations of oxygen, improving shelf life and reducing discoloration, but during preparation meat rapidly turns brown, increasing the risk of consumption before it is properly cooked.

Minced beef and fresh strawberries were identified as two new possible sources of infection and both are being examined by the Danish Food and Veterinary Administration as part of the national action plan against Campylobacter.

Environmental factors and animal contact accounted for a sizeable proportion of domestic Campylobacter infections in the age group studied.

Eating in a café/restaurant or fast food outlet carried an increased risk of infection as did eating food served outdoors and own food consumed during a picnic in the countryside or forest. Eating meat cooked on a barbecue at home was also associated with infection. For hygiene practices at home, handling of fresh chicken in the 5-day exposure period was associated with increased risk of infection.

Cases were more likely than controls to have consumed unpasteurized, raw milk and to live in a household with drinking water supplied from a private supply. Fresh strawberries, raspberries, and blueberries increased risk of infection as did smoothies prepared with frozen berries.

Campylobacter remains primarily a foodborne infection albeit with an environmental component. Results suggested that campylobacteriosis is not attributable to one primary food source but rather a combination of non-food and food factors. The importance of these is likely to vary between persons, locations, and throughout the year.

More outbreaks than thought

Another study involving SSI has shown that Campylobacter case clustering and outbreaks appear to occur more often than previously assumed.

The research, in the Clinical Microbiology and Infection journal, applied whole genome sequencing to 245 Campylobacter jejuni isolates from patients with domestically acquired infection over nine months in 2015 and 2016.

Outbreaks have been linked to contaminated water, raw (unpasteurized) milk, animal contact, and environmental exposures such as mud and sand.

WGS demonstrated 62 of the 245 isolates clustered genetically. In total, 21 genetic clusters were identified of which four consisted of five isolates or more. Seventeen of the 21 genetic clusters were clustered in space and/or time. Of the 245 isolates, 49 were part of a temporal and/or geographical cluster. The identified clusters included two outbreaks; one which had not been identified through the existing surveillance system.

Campylobacter stable at EU level

Meanwhile, recently released data from the European Centre for Disease Prevention and Control (ECDC) showed there were almost 250,000 confirmed cases of campylobacteriosis in Europe in 2016.

Campylobacter has been the most common gastrointestinal bacterial pathogen in Europe since 2005. There was a significantly increasing trend in campylobacteriosis from 2008–2016 but in the last five years (2012–2016), it has been stable, with no statistically significant increase or decrease.

In 2016, the Czech Republic, Germany, Spain and the UK accounted for 69.8 percent of confirmed cases. Czech Republic, Slovakia and Sweden had the highest notification rates and the lowest were in Bulgaria, Cyprus, Latvia, Poland, Portugal and Romania. Compared with 2015, notification rates increased in 20 countries and decreased in seven. Sweden’s high notification rate was mostly due to an outbreak in 2016-2017 from poultry meat which led to an estimated 5,000 more cases than normal levels.

The notification rate in Germany increased 15 percent in 2012–2016, while in the UK it decreased 21 percent in the same period.

Sixty-two deaths attributed to campylobacteriosis were reported in 2016 compared to 60 in 2015. Of reported deaths in confirmed cases, 76.4 percent were in the age group 65 years and older. Children under five years accounted for 13.4 percent of 248,382 confirmed cases with known age.

Cases followed a clear seasonality consistent with previous years with most reported from June to August. Smaller January peaks were observed in 2012–2016.