Researchers in the United Kingdom have shared findings from recent outbreak investigations ranging from contaminated raw milk cheese to illnesses traced to petting zoos.
The European Centre for Disease Prevention and Control (ECDC) organized the European Scientific Conference on Applied Infectious Disease Epidemiology (ESCAIDE).
A long-standing reptile-associated Salmonellosis outbreak, identified in the UK in 2015 through whole genome sequencing, was linked to frozen feeder mice contaminated with Salmonella Enteritidis. Control measures at the implicated production farm and targeted public health messaging failed to reduce the number of cases. In February 2022, a ban was imposed on imports of feeder mice from the farm in Lithuania.
Overall, 961 cases were reported from 2014 to 2023, with 3 percent being notified during the post-ban period. There were 170 cases in 2021 and 31 in 2023. The monthly median reported decreased from 8 in the pre-ban phase to 4 in the post-ban period. This includes nine in March 2022 and one in December 2023. Although low in number, patients are still being identified post-ban, likely due to the use of frozen feeder rodents imported before the rule change.
“The feeder-mice ban appeared to have significantly reduced the notification of cases, demonstrating the effectiveness of the import ban, unlike previous control measures,” said scientists.
Raw milk cheese outbreak
In November 2023, national gastrointestinal infections surveillance identified an outbreak of STEC O145:H28 in England and Scotland. Of 36 confirmed cases, with symptom onset between July 25 and Dec. 23, 2023, 54 percent were female, and the age range was 2 to 81. England had 29 cases. Overall, 65 percent of patients reported bloody diarrhea, 58 percent were hospitalized, and one developed Hemolytic Uremic Syndrome (HUS) and died.
The source was detected through the unusual association with domestic travel. An investigation identified unpasteurized cheese produced by Mrs. Kirkham’s and served on a charcuterie platter by one train operator as the vehicle in 16 cases; one person purchased cheese from the implicated farm shop. The product was recalled in December 2023.
Of 43 cheese samples tested, STEC DNA was detected twice. One was sequenced but was O109:H16.
Also, 28 environmental samples were taken from the farm. Two cattle fecal samples were positive for the outbreak strain and matched human cases.
In July 2024, the UK Health Security Agency (UKHSA) notified the Food Standards Agency (FSA) of four cases between June and July, taking the number of sick people to 40, including two deaths. One death was part of the latest update. While there was a microbiological link between the later patients and previous cases, investigations did not identify a food chain connection between them and Mrs. Kirkham’s products.
“We recommend clearer labeling of unpasteurized cheese highlighting the risks posed to vulnerable groups, and wider non-O157 STEC testing at frontline laboratories,” said scientists.
Petting farm risks
Experts have looked at potential associations between increasing E. coli O26 and farm or nursery attendance in the seven days before illness onset.
There were 7,011 STEC cases studied, rising from 1,112 in 2019 to 1,946 in 2023. O26 infections increased from 9.2 percent of cases in 2019 to 12.2 percent in 2023. They also had a higher risk of hemolytic uremic syndrome (HUS) than non-O26 infections.
For more than 4,000 cases with exposure information, 459 attended farms and 546 nurseries, which remained similar over time. Amongst 0—to 4-year-olds, the proportion of cases with O26 was higher in those who visited farms than those who attended nursery.
The study proved that O26 is associated with farm or nursery attendance among children. It reinforces the need to investigate cases promptly, ascertain exposures to risk settings, and identify and mitigate related outbreaks. Less than half of labs in England can detect non-O157 STEC, so the true burden of O26 is unclear.
During March and April 2024, 59 lab-confirmed Cryptosporidium cases linked to a working farm offering a lamb-feeding experience were notified to Public Health Wales. Environmental investigations highlighted multiple risk factors, and microbiological efforts genetically linked lambs to outbreak cases.
Of the 540 responses to a study, scientists identified 168 cases. They were mostly female and ranged from 1 to 80 years old. Children were more likely to get sick. Cases were less likely to have thoroughly washed their hands and more likely to have had visible feces on their person or kissed/had face-contact with lambs. It was the largest Cryptosporidium outbreak associated with a farm setting in Wales.
Researchers said farms should limit animal contact at these events, and revisions to codes of practice may be necessary. Enhancing risk awareness among farmers and visitors, particularly for children, and ensuring the availability of adequate sanitization facilities are also needed.
Finally, a sharp increase in brucellosis incidence was observed in northwestern Tajikistan from 2022 to May 2023. Of 103 cases, 84 were from the same village. Common symptoms were joint pain, fever, weakness, and night sweats.
Brucellosis was associated with the consumption of homemade kaymak (clotted cream from unpasteurized milk). It was also linked to homemade meat, neighborhood milk, animal slaughter, and animal grooming.
Contact with unvaccinated livestock or consumption of their products was a key contributor to the outbreak. Following the investigation, an education and vaccination drive was carried out and no brucellosis cases were reported after August 2023.
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