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Researchers warn against raw milk, cheese after testing dairies

Research recently published by scientists in The Netherlands shows that E. coli and Campylobacter bacteria are so common on goat and sheep dairy farms that pasteurization is necessary to prevent contamination of raw milk and products made with it.

The Dutch National Institute for Public Health and the Environment and the Dutch Food and Consumer Product Safety Authority joined forces for the project. The government agencies annually investigate how common pathogens of zoonoses are on different types farms. Cattle, meat pig and laying hen operations have already been examined.

For the recent report, scientists looked at 181 dairy goat farms and 24 dairy sheep farms. Shiga-toxin-producing E. coli (STEC) and Campylobacter bacteria was found on most of the animals. The pathogens were also found among farmers and their family members.

“STEC appeared on virtually all the farms studied,” according to the research report.

“Campylobacter has been demonstrated in one out of three goat farms (33 percent) and almost all sheep farms (96 percent).”

Listeria was less common. It was found on about 9 percent of the goat farms and 17 percent of the sheep farms. It was not found in farmers and their families. The percentage of farms with Listeria is relevant, the researchers wrote, because “unpasteurized soft cheese is the most important source of Listeria infection in humans.”

The study also looked at Salmonella and ESBL-producing bacteria, which were not very common on the farms that were surveyed.

Bacteria including E. coli lives in animals’ intestines and is shed in their manure. The pathogens cannot be seen by the human eye and tiny amounts can be life threatening to humans.

“A small amount of manure can contaminate raw milk or raw milk cheese,” the researchers said. “Contamination can be prevented by drinking only pasteurized milk.”

Infection of pathogens like STEC, Campylobacter and Listeria are often present in farm environments and can infect people who have contact with the animals, their bedding, manure and other environmental surfaces. Along with owners, visitors can reduce the risk of illness by washing their hands after contact with the animals or their environment.

The study concluded that the pasteurization of milk, paired with proper hygiene after visiting or working with farm animals, is key to preventing disease.

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