Mar 2, 2007 (CIDRAP News) Federal health officials are using an analysis of an Escherichia coli O157:H7 outbreak that involved 18 cases in December 2005 to remind people of the dangers of drinking unpasteurized milk.
The outbreak was traced to a farm in Cowlitz County, Washington, that ran a cow-share program, in which people bought interests in dairy cows and received raw milk in return, according to the Centers for Disease Control and Prevention (CDC).
By interviewing 43 of 45 families who held shares in the cows, health investigators found 18 cases of E coli infection, 8 of which were laboratory-confirmed, according to the report in today's Morbidity and Mortality Weekly Repor (MMWR). The 18 case-patients constituted 13% of the 140 people who reported drinking raw milk from the farm.
Five patients were hospitalized, and four of them had hemolytic uremic syndrome (HUS), a potentially fatal kidney disorder. The hospitalized patients were all children (aged 1 to 13).
Investigators analyzed the DNA fingerprints of E coli O157:H7 from eight patients and found that seven of them matched one another and also matched isolates from milk samples and environmental samples from the milking-parlor floor, the report says. In addition, there was a dose-response relationship between milk consumption and the risk of illness, with a 37.5% risk for those who drank 3 or more cups daily.
Raw milk can be sold legally in Washington state under a licensing system, but the farm blamed for the outbreak was not licensed, according to the CDC. Inspectors said they found mud and manure on the floor of the milking area, inadequate handwashing facilities, and improper procedures for cleaning equipment.
In a news release yesterday, the Food and Drug Administration said raw milk can be contaminated not only with E coli, but also with Salmonella, Listeria, Campylobacter, and Brucella species.
The MMWR report says 33 outbreaks linked to raw milk, involving E coli O157:H7, Salmonella, and Campylobacter, were reported to the CDC from 1988 through 2005.
The FDA statement listed higher numbers, saying the CDC identified 45 outbreaks linked to raw milk or cheese made from raw milk between 1998 and May 2005. Those outbreaks involved 1,007 illnesses, 104 hospitalizations, and 2 deaths. The statement didn't specify whether this included all pathogens, and FDA officials could not be reached for clarification this afternoon.
Raw milk has been banned from interstate commerce since 1987, but it can be sold legally in 27 states. However, "Because raw milk certification has failed to prevent many raw-milk-associated infections in the past, consumers should not assume that certified raw milk is free of pathogens," the CDC says.
The FDA noted that proponents of raw milk claim that it is more nutritious than pasteurized milk and is inherently antimicrobial. "Research has shown that these claims are myths," the statement said.
CDC. Echerichia coli O157:H7 infection associated with drinking raw milkWashington and Oregon, November-Decmeber 2005. MMWR 2007 Mar 2;56(8):165-7 [Full text]
FDA news release