MADISON — DNA test results and other evidence have now established that an outbreak of illness involving at least 35 people, the majority children and teens, was linked to drinking unpasteurized milk. Wisconsin food safety officials are cautioning consumers not to drink raw milk and farmers not to sell it to the public.
"Laws requiring pasteurization of milk have been on the books for more than half a century, and there are good public health reasons for that," said Steve Ingham, head of the Food Safety Division in the Department of Agriculture, Trade and Consumer Protection.
"We have very compelling evidence linking these illnesses to drinking raw milk. This is the third major outbreak in Wisconsin since 2001 that has been tied to raw milk consumption. That’s not to mention a number of smaller ones in which the link was strongly suspected, but patients were unwilling to identify farms that provided the milk. So far we’ve been fortunate that the infections have not been life-threatening, but raw milk is an inherently risky food and it can lead to other, more dangerous illnesses, including E. coli 0157:H7 infection."
An epidemiologic investigation conducted by DATCP and the Wisconsin Department of Health Services has found 35 confirmed cases of Campylobacter jejuni infection, including 21 patients under age 18. One person was hospitalized. All the patients had consumed unpasteurized milk. Thirty of the patients identified Zinniker Family Farm, Elkhorn, as the source of the raw milk. The farm sells raw milk through a "cow-share" program. Twenty-seven of the confirmed cases were in Walworth and Waukesha counties; the rest were in Racine and Kenosha counties.
Additional testing showed that the Campylobacter jejuni isolated from 25 of the patients — all linked to Zinniker Family Farm — had the same DNA fingerprint. Manure samples obtained directly from milking cows on that farm also tested positive for Campylobacter jejuni with the same DNA fingerprint. Manure on the cows’ udders or in the milking barn environment can contaminate milk. Pasteurization kills Campylobacter jejuni and other disease-causing bacteria in milk.
Campylobacter jejuni are bacteria that cause symptoms including diarrhea, abdominal cramping, fever, nausea and vomiting. Rarely, an infection may lead to paralysis, which may require hospitalization and artificial respiration. This generally occurs after the initial symptoms have disappeared. Campylobacter can be transmitted by consuming food contaminated by animal feces or handled by someone with the infection who has not adequately washed his/her hands after using the bathroom.
Milk samples from the farm taken after the initial outbreak did not test positive, which is not unusual, Ingham said. Cattle shed the bacteria intermittently, so the bacteria may not have been present when the samples were taken. Changes in sanitation procedures could also explain the absence of bacteria in later milk samples, he said.
Because Zinniker Family Farm sells milk to a defined customer list, there is little risk to the general public in this case. However, the outbreak should discourage consumers from joining "cow-share," membership, or other similar arrangements to buy raw milk, and should discourage dairy producers from adopting such an arrangement for their farms, Ingham said.
"Selling raw milk to consumers is illegal in Wisconsin. Some farmers believe that such arrangements exempt them from the law. They are mistaken. The law says that owners may consume raw milk from their farms, but those owners have to be true owners with a real financial stake in the farm. And the law clearly says that unpasteurized milk can be sold only to a licensed dairy plant or to other licensed businesses that sell to dairy plants," he said.
Other outbreaks in Wisconsin that have been tied to raw milk include:
* In December 2001, at least 30 laboratory-confirmed cases of Campylobacter jejuni were identified in northwestern Wisconsin, all tied to a cow-share program.
* In June 2006, 19 laboratory-confirmed and 39 probable cases of Campylobacter jejuni infection were traced to cheese curds made from unpasteurized milk in an unlicensed facility by an unlicensed cheese maker in Ashland. The cases occurred in many Wisconsin counties and six other states.
Nationwide, the Centers for Disease Control and Prevention report that 45 outbreaks tied to unpasteurized milk or cheese consumption occurred from 1998 to 2005. These outbreaks occurred in 22 states, two were multi-state outbreaks, and they resulted in 1,000 illnesses, 104 hospitalizations and two deaths.
In an article published in the Wisconsin Medical Journal in August 2000, the Wisconsin Division of Public Health reported that from 1992 to 1999, consumption of raw milk and raw milk products was one of the top three risks for E. coli 0157:H7 infection in Wisconsin. E. coli 0157:H7 infections can be fatal.