Three people fell ill after drinking pasteurized milk from a farm in England in 2021, according to recent study results.
The Cryptosporidium parvum outbreak was linked to milk from a vending machine.
Post-pasteurization contamination was the source of the outbreak, according to the study published in Epidemiology and Infection. It is thought to be the first documented Cryptosporidium outbreak associated with pasteurized dairy from a milk-vending machine.
On-farm milk vending machines are increasingly common and may represent an emerging public health risk, said researchers.
Human and animal samples match
In March 2021, three cases of laboratory-confirmed Cryptosporidium infection were notified. They had common exposure to a farm-based milk-vending machine. Although onset dates were spread over 35 days, this exposure was notable and of public health concern, according to the study.
A total of 33 cases of cryptosporidiosis were identified over a set period in the South West region. Questionnaire data were available for 26 of them. However, no further cases beyond the initial three had consumed milk from a vending machine.
The three sick people who had bought pasteurized milk from the vending machine were a 51-year-old man, a 78-year-old woman and a 41-year-old man.
Cryptosporidium parvum detected in human cases was indistinguishable from that in a calf on the farm.
This farm is a multi-generational family run dairy where the majority of milk is sold for wholesale processing. A small quantity of milk is pasteurized onsite, and cheese and eggs are also sold.
There has been an increase in the sale of milk products across South West England in recent years. Farmers are sometimes unaware they need to register as a food business to sell direct-to-consumer products, so the scale of on-farm pasteurized milk sales is not known, said scientists.
Problems after pasteurization
An Environmental Health Officer (EHO) inspected the farm and rated it 1 out of 5, or major improvement necessary on the Food Hygiene Rating Scheme (FHRS) scale, and served hygiene improvement notices.
Although pasteurization was achieved and validated with phosphatase test results and temperature records, concern was raised about the cleaning of equipment and the vending machine churns, particularly after pasteurization.
EHOs took further samples from the milk vending machine for hygiene indicators, two months after the initial improvement notice. These samples had unsatisfactory levels of Enterobacteriaceae, an indicator of post-pasteurization contamination.
The Food Standards Agency (FSA) inspected the farm and concluded inadequate cleaning after pasteurization was a potential contamination route and made recommendations to improve the situation.
Routine cleaning and disinfection procedures on-farm are not enough to remove Cryptosporidium oocysts. General farm hygiene, pasteurization and post-pasteurization hygiene are critical control points, according to the study.
Researchers recommended that existing on-farm pasteurization guidance is reviewed, to cover milk vending machines. This may include resources for EHOs as well as information and training for manufacturers, users and suppliers of equipment.
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