Clostridium perfringens has been confirmed as the cause of more than 100 students falling ill at a university in New Zealand.
Health New Zealand and the Ministry for Primary Industries (MPI) investigated the outbreak among pupils at the University of Canterbury’s University Hall in Christchurch. Students fell ill a few weeks ago during the end-of-year exam period.
Laboratory testing and survey data confirmed New Zealand Food Safety’s theory that the outbreak was likely caused by unsafe preparation of shredded chicken served to students as part of a meal.
Clostridium perfringens and its toxin were detected in fecal samples from students who became sick. The illness usually follows the consumption of food that has been kept at unsafe temperatures for too long.
An epidemiological analysis of student survey responses found that eating the shredded chicken dish was the biggest indicator of illness.
Vincent Arbuckle, New Zealand Food Safety’s deputy director-general, said: “Unsafe handling practices around cooling, reheating and hot holding of the meat is consistent with how toxins from the bacteria grow and cause illness.
“The time between eating the food and symptoms appearing was, on average, about 11 hours, which is typical of this pathogen. If the issue was undercooked meat, we would expect to see a different pathogen, other symptoms of illness, and a different incubation period, typically around two to five days.
“This conclusion is supported by data collected by the National Public Health Service, including fecal samples provided by some affected students, and a survey of students to establish what they ate and the symptoms they experienced.”
Safe preparation is essential for caterers
Arbuckle stressed the importance of safe food preparation.
“Businesses which cater to large numbers of people, such as university halls of residence, need to make sure that where they prepare and cook food in bulk, they have good processes in place to ensure risk is properly managed. In particular, cooling and reheating must be carefully managed to prevent pathogens from growing, and particular care must be taken when keeping food for later service,” he said.
“Students can be assured that food safety officers have fully inspected the kitchen and found no evidence of immediate and ongoing food safety risk at the hall. If we thought students were at risk, we would take further action to prevent it. Our work to review the kitchen’s practices and procedures to prevent the issue from arising again continues.”
In 2023, 27 outbreak-related cases of confirmed Clostridium perfringens intoxication were reported in EpiSurv, New Zealand’s national public health surveillance database. In March, chicken and lamb souvlaki were the suspected source of three illnesses. A chicken curry from a caterer consumed at home was behind 12 illnesses. The source for another outbreak with a dozen cases was not found.
Meanwhile, an outbreak of norovirus was reported in August 2024, involving 49 cases, of which four were confirmed and the rest were probable. It was linked to oyster consumption at several restaurants in the Auckland region. Genotyping of three outbreak samples revealed an identical strain, supporting a common source exposure. In late August, the supplier, Te Matuku Oysters, issued a food recall.
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