A ProMed-mail post (September 16, 2009)
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 [DATCP].
“We have very compelling evidence linking these illnesses to drinking raw milk. This is the 3rd 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. 30 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. 27 of the confirmed cases were in Walworth and Waukesha counties; the rest were in Racine and Kenosha counties.
Additional testing showed that the C. 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 C. jejuni with the same DNA fingerprint. Manure on the cows’ udders or in the milking barn environment can contaminate milk. Pasteurization kills C. jejuni and other disease-causing bacteria in milk.
C. jejuni is a bacterium that causes symptoms including diarrhea, abdominal cramping, fever, nausea and vomiting. Rarely, an infection may lead to Guillain-Barre syndrome, a nervous system disease, which may require hospitalization and artificial respiration. This generally occurs after the initial symptoms have disappeared. The infection 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 also could 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 C. jejuni were identified in northwestern Wisconsin, all tied to a cow-share program; – in June 2006, 19 laboratory-confirmed and 39 probable cases of C. 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 6 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 1000 illnesses, 104 hospitalizations, and 2 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.
ProMED-mail Rapporteur Susan Baekeland
Regarding whether raw milk safety and its increased nutritional value has been “adequately documented by both the USDA and the FDA, the following is from the FDA in 2004, “Got Milk? Make Sure It’s Pasteurized”:
“Pasteurization, since its adoption in the early 1900s, has been credited with dramatically reducing illness and death caused by contaminated milk. But today, some people are passing up pasteurized milk for what they claim is tastier and healthier “raw milk.” Public health officials couldn’t disagree more.
Drinking raw (untreated) milk or eating raw milk products is “like playing Russian roulette with your health,” says John Sheehan, director of the Food and Drug Administration’s Division of Dairy and Egg Safety. “We see a number of cases of foodborne illness every year related to the consumption of raw milk.”
More than 300 people in the USA got sick from drinking raw milk or eating cheese made from raw milk in 2001, and nearly 200 became ill from these products in 2002, according to the CDC.
Raw milk may harbor a host of disease-causing organisms (pathogens), such as the bacteria Campylobacter, E. coli, Listeria, Salmonella, Yersinia, and Brucella. Common symptoms of foodborne illness from many of these types of bacteria include diarrhea, stomach cramps, fever, headache, vomiting, and exhaustion. Most healthy people recover from foodborne illness within a short period of time, but others may have symptoms that are chronic, severe, or life-threatening.
People with weakened immune systems, such as elderly people, children, and those with certain diseases or conditions, are most at risk for severe infections from pathogens that may be present in raw milk. In pregnant women, Listeria monocytogenes-caused illness can result in miscarriage, fetal death, or illness or death of a newborn infant. And E. coli infection has been linked to hemolytic uremic syndrome, a condition that can cause kidney failure and death.
Some of the diseases that pasteurization can prevent are tuberculosis, diphtheria, polio, salmonellosis, strep throat, scarlet fever, and typhoid fever.
Pasteurization and Contamination
The pasteurization process uses heat to destroy harmful bacteria without significantly changing milk’s nutritional value or flavor. In addition to killing disease-causing bacteria, pasteurization destroys bacteria that cause spoilage, extending the shelf life of milk.
Milk can become contaminated on the farm when animals shed bacteria into the milk. Cows, goats, and sheep carry bacteria in their intestines that do not make them sick but can cause illness in people who consume their untreated milk or milk products.
But pathogens that are shed from animals aren’t the only means of contamination, says Tom Szalkucki, assistant director of the Wisconsin Center for Dairy Research at the University of Wisconsin-Madison. Cows can pick up pathogens from the environment just by lying down, giving germs the opportunity to collect on the udder, the organ from which milk is secreted. “Think about how many times a cow lays down in a field or the barn,” says Szalkucki. “Even if the barn is cleaned thoroughly and regularly, it’s not steamed. Contamination can take place because it’s not a sterile environment.”
The Health Hype
Raw milk advocates claim that unprocessed milk is healthier because pasteurization destroys nutrients and the enzymes necessary to absorb calcium. It also kills beneficial bacteria and is associated with allergies, arthritis, and other diseases, they say.
This is simply not the case, says Sheehan. Research has shown that there is no significant difference in the nutritional value of pasteurized and unpasteurized milk, he says. The caseins, the major family of milk proteins, are largely unaffected, and any modification in whey protein that might occur is barely perceptible.
“Milk is a good source of the vitamins thiamine, folate, B-12, and riboflavin,” adds Sheehan, “and pasteurization results in losses of anywhere from zero to 10 percent for each of these, which most would consider only a marginal reduction.”
While the major nutrients are left unchanged by pasteurization, vitamin D, which enhances the body’s absorption of calcium, is added to processed milk. Vitamin D is not found in significant levels in raw milk.
“Pasteurization will destroy some enzymes,” says Barbara Ingham, PhD, associate professor, and extension food scientist at the University of Wisconsin-Madison. “But the enzymes that are naturally present in milk are bovine enzymes. Our bodies don’t use animal enzymes to help metabolize calcium and other nutrients.”
“Enzymes in the food that we eat and drink are broken down in the human gastrointestinal tract,” adds Ingham. “Human bodies rely on our own native enzymes to digest and metabolize food.”
“Most of the native enzymes of milk survive pasteurization largely intact,” says Sheehan, “including those thought to have natural antimicrobial properties and those that contribute to prolonging milk’s shelf life.” Other enzymes that survive are thought to play a role in cheese ripening.
Ingham says that pasteurization will destroy some bacteria that may be helpful in the fermentation of milk into products such as cheese and yogurt, “but the benefit of destroying the harmful bacteria vastly outweighs the supposed benefits of retaining those helpful microorganisms. Plus, by adding the microorganisms that we need for fermentation, we can assure a consistently high quality product.”
Science has not shown a connection between drinking raw milk and disease prevention. “The small quantities of antibodies in milk are not absorbed in the human intestinal tract,” says Ingham. “And there is no scientific evidence that raw milk contains an anti-arthritis factor or that it enhances resistance to other diseases.”
Fans of raw milk often cite its creamy rich taste, says Szalkucki, who adds that it may be creamier because it is not made according to the standards for processed milk. “If you go to a grocery store and buy fluid milk, it’s been standardized for a certain percentage of fat, such as 2 percent,” he says. “Raw milk is potentially creamier because it has not been standardized and it has a higher fat content.”