Public health officials in Sweden have closed an investigation into a spike in Campylobacter infections linked to chickens raised for meat production after levels returned to normal.

There had been a rise in Campylobacter infections linked to Swedish broilers since August. There was a temporary decline in September before cases started going up again in October.

It has been going on in parallel with an increased proportion of Campylobacter-positive broiler flocks until the second half of November.

During August to November, several people who work at a large slaughterhouse run by Kronfagel in Sörmland also fell ill.

Folkhalsomyndigheten (Public Health Agency of Sweden) reported the same types of Campylobacter have been identified in patients and among broilers. A large proportion of the matching isolates came from the slaughterhouse in Sörmland that was also involved in the occupational infections.

Return to lower levels
In total, 50 cases were reported from Sept. 21 to 27 before numbers increased to about 100 per week during mid- to late October. There were around 70 to 80 weekly infections during November and for the past two weeks the figure has been about 30 cases per week.

The outbreak was widespread in all regions of the country with slightly more men than women sick and infections mostly in people aged between 40 and 70 years old.

Rikard Dryselius, a microbiologist at Folkhalsomyndigheten, said there was a sharp decline in the number of people with Campylobacteriosis between Nov. 23 to 29 and Nov. 30 to Dec. 6, from close to 70 reported cases to about 30.

“The number of cases appeared to remain at around 30 during Dec. 7 to 12 and reports from the Swedish National Veterinary Institute (SVA) indicated that the proportion of Campylobacter positive poultry flocks since Nov. 2 to 8 was back to the low levels that prevailed before the large increase in mid-July,” he said.

“Apart from this, we had also received information via the animal health authorities that insufficient cleaning of transport crates sent out to different farms from the slaughterhouse in Sörmland was likely to have contributed to the spread between farms. It is worth noting that dirty transport cages was also a major contributor to the large outbreak in Sweden during 2016-2017. Then, however, the producer reported it was a faulty connection that caused the cages to be rinsed with dirty water.”

Domestically-produced chicken was the cause of a Campylobacter outbreak in 2016 to 2017, the largest identified foodborne outbreak in Sweden for more than 50 years. This resulted in an estimated 5,000 more Campylobacter cases being reported in the country between August 2016 and May 2017 than normal levels.

Folkhalsomyndigheten said it was important that chicken producers try to reduce the risk of infection and that consumers always practice good food hygiene when handling fresh chicken.

Kronfagel and the Swedish University of Agricultural Sciences (SLU) are working on a project to reduce Campylobacter and other pathogenic bacteria in ready-to-eat chicken. Production and slaughter are being studied to find solutions that can cut the amount of disease-causing bacteria.

Aussie summer warning
Meanwhile, a health agency in an Australian state is urging people to take care when handling food following a recent increase in the number of cases of gastroenteritis caused by Campylobacter.

As the region comes into the warmer summer weather, gastroenteritis caused by bacteria tends to increase, according to the Southern New South Wales Local Health District (SNSWLHD).

For a week in November, 26 people in SNSWLHD were reported with Campylobacter, compared to 14 at the same time in 2019. The public health unit is investigating to see if there are links between recent cases or any shared sources of infection.

April Witteveen, manager of infectious diseases for SNSLWHD, said bacterial gastroenteritis was often spread by contaminated food or water, or sometimes through direct contact with an infected person.

“Campylobacter is frequently associated with the consumption of contaminated poultry. It is important to ensure all chicken is thoroughly cooked through before eating. The best defense against Campylobacter is to wash hands immediately after handling raw poultry and before handling any cooked or ready-to-eat foods. Thoroughly wash hands with soap and running water for at least 10 seconds before handling and eating food,” she said.