A new report describes how raw, unpasteurized milk in Tennessee likely caused infections in people, including infants, one of whom developed kidney failure.

The report from the Center for Infectious Disease Research & Policy (CIDRAP) discusses two babies who developed E. Coli infections after being fed raw milk from a cow-sharing arrangement in Tennessee.

Often called “herd-shares,” such arrangements get around bans on raw milk sales by legally allowing people to buy part of a herd or of a single animal so that they can consume unpasteurized milk. Participants in herd-share operations pay a farmer to care for and milk the animals.

The babies discussed in the new CIDRAP report developed diarrhea between July 25 and Aug. 1, 2022. Testing revealed Shiga toxin-producing E. coli (STEC). Both households received raw milk from participants in the same cow share. The baby who developed kidney failure (hemolytic uremic syndrome) was hospitalized for 27 days.

The Tennessee Department of Health (TDH) investigated the cow-share program, which included 7 to 10 cows that were hand-milked daily. The investigators obtained a list of raw milk consumers and identified five patients with STEC infections, with two confirmed in hospitalized infants; no deaths were reported. 

“In Tennessee, direct sale of raw milk is prohibited, and TDH advises against raw milk consumption; however, sharing of raw milk through cow-share arrangements is legally permitted,” the report authors said. 

“This outbreak highlights the risk for severe illness associated with cow-share arrangements, especially among young children, who are at increased risk for STEC-related HUS. The outbreak also demonstrated that households not formally participating in cow-share arrangements can be affected.”

Investigators identified possible routes of fecal contamination during milking and possible milk storage at temperatures higher than recommended, with cooling facilitated by the mechanical circulation of cool spring water followed by immersion of milk containers in ice-filled coolers. Samples were taken from eight sites including a milk filter, a collection pail, barn posts, and four manure locations, as well as a sample of raw milk.

The Tennessee health department conducted case finding among cow-share participants and found the list included 125 participants from Georgia, Tennessee, and North Carolina. Federal law prohibits the transport and sale of raw milk across state lines.

Researchers reported that a U.S. Department of Agriculture laboratory identified two isolates of STEC O157:H7 from a single cattle manure sample in the dairy farm’s milking barn. Whole genome sequencing conducted demonstrated that human and cattle stool isolates were highly related, with zero allele differences detected.

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