MDA/MDH investigation into E. coli O157:H7 illnesses and Raw Milk Consumption from Hartmann farm
What evidence do you have that raw milk from the Hartmann farm caused the illnesses?
This investigation began like many other foodborne investigations: Someone becomes ill, sees their physician and the physician sends a stool specimen to a clinical laboratory. If that laboratory finds, or “isolates”, one of a number of illness-causing bacteria (eg., Salmonella, E. coli O157:H7), they send that bacterial isolate to the MDH Public Health Laboratory (PHL) for further testing. Each bacterial isolate is DNA fingerprinted by a technique called pulsed-field gel electrophoresis (PFGE).
During May 2010, E. coli O157:H7 isolates from 5 patients sent by separate clinical laboratories to the MDH PHL were found to all have the same DNA fingerprint by PFGE testing. Since then, three additional cases have been identified with an identical DNA fingerprint, brining the total number of cases to eight.
This particular DNA fingerprint type (which also can be called a “strain”) of E. coli O157:H7 had never been seen before in Minnesota. The fact that multiple patients all were infected with this new strain in such a tight timeframe indicates that there was a common source for the illnesses. In other words, the patients must have acquired their infection from the same source.
In any foodborne illness investigation, MDH epidemiologists interview patients about an extensive array of possible exposures. These interviewers use a standard questionnaire and interview technique. This includes asking questions about what the ill people ate, including meat, produce and other food items. It also includes questions about recreational water and drinking water, contact with animals, daycare attendance, and more.
In this outbreak, the ill people came from communities across Minnesota and the only exposure the cases had in common was consumption of raw dairy products from the Hartmann farm or exposure to an ill household member who consumed the product. This connection, and the fact that the same strain of E. coli O157:H7 found in the ill people was found in several animals and from several environmental samples on the Hartmann farm, clearly indicates that the farm was the source of the E. coli O157:H7 that made the people ill.
What is the significance of finding E. coli O157 in the environmental samples from the farm?
The strain found on the farm matches the strain found in the cases of illness. Again, this is a strain that has never been seen before in Minnesota.
This tells us that the bacteria that sickened the people was on the Hartmann farm and since several of the people that became ill never visited the farm, their only potential source would have been food products from the farm.
Did you find the outbreak strain in dairy product from the cases’ homes or from the farm?
The outbreak strain of E. coli O157:H7 has not been found in product yet. However, product samples that were collected from the farm were obtained one week to several weeks after production of products that made people sick. Other strains of Shiga toxin-producing E. coli were found, indicating an ongoing problem with contamination.
The fact that the outbreak strain was not found in samples of product taken from the farm or homes does not mean it wasn’t in the product that sickened the individuals. In many cases, only particular batches of product may have been contaminated. The product from the contaminated batches may not be available for testing because it has already been consumed. Even if the contaminated batches are available for testing, the contamination may not be uniformly distributed throughout the product. It can be difficult to find the “needle in the haystack” when only small amounts of product are able to be used for a laboratory test. The fact that some pathogen was not found in a sample taken today does not mean it wasn’t there yesterday or a week ago, or won’t be there tomorrow. Also, since raw milk contains many types of bacteria it is a difficult process to isolate individual bacteria growths and find the disease-causing strains.
The outbreak strain of E. coli O157:H7 was found in the manure of some individual calves, sheep, and cattle pens. Of note, the calves were likely drinking the same milk as that consumed by the cases.
Standard public health practice does not require finding the illness strain of pathogen in either environmental or product samples in order to determine the source of an outbreak and before intervention to prevent further illness should be initiated. In fact, it is quite rare in foodborne investigations that food product is available for testing as it is often perishable or has been completely consumed by the time the outbreak is recognized. State health and agriculture officials often act on epidemiologic evidence to remove contaminated products from the marketplace and prevent additional illnesses. Indeed, to do nothing in the face of such compelling evidence would be irresponsible – regardless of the size or nature of operation implicated.
Are there more cases being investigated?
Yes, MDH has received additional reports of illness in several consumers of Hartmann dairy products that it is investigating.
Why are you so convinced that raw milk is unsafe?
Raw milk has been found to contain numerous pathogens that can cause serious illness, including Campylobacter, Shiga toxin-producing Escherichia coli, Salmonella, Listeria, Yersinia and Brucella and the bacteria that cause bovine tuberculosis. In fact, pasteurization was developed many years ago as a way to reduce diseases that were commonly caused by raw milk.
Getting sick from one of these germs can lead to a wide variety of illness manifestations. Some germs cause diarrhea, vomiting, stomach cramps, fever, headache, and body aches lasting for a couple of days to several weeks. Most healthy people with this type of illness recover, but hospitalization rates are usually 10-30%. Severe complications can include bloodstream infections, a polio-like paralysis, kidney failure, and death. For example, E. coli O157:H7 infections lead to a severe complication called hemolytic uremic syndrome (HUS) in 10% of children (even previously health children), and HUS is fatal 5% of the time. In addition HUS survivors often suffer from lifelong medical issues, including the need for kidney transplants in some.
Illnesses from raw milk are particularly dangerous for people with weakened immune systems, such as the elderly, children, and people with cancer, an organ transplant, or HIV/AIDS. Germs found in raw milk and raw dairy products can be especially dangerous to pregnant women, sometimes leading to abortion, stillbirth, or severe disease in newborns.
Between 1973 and 1992, 46 outbreaks associated with raw milk consumption were reported to the Centers for Disease Control and Prevention. An additional 45 outbreaks were reported to CDC between 1998 and May 2005, accounting for 1,007 illnesses, 104 hospitalizations, and two deaths.
What is pasteurization?
Pasteurization is simply the process of heating milk for a set period of time to a specific temperature to kill any bacteria that might be present in the milk. By heating the milk, bacteria that cause human illness are killed or inactivated. This process was discovered by Louis Pasteur over 120 years ago.
What about the health benefits often mentioned by raw milk proponents?
According to the FDA, CDC and other scientific bodies, there is no meaningful difference in the nutritional value of pasteurized and unpasteurized milk. Pasteurization is the only effective method for eliminating the bacteria in raw milk and milk products. Pasteurization uses heat applied for a length of time sufficient to destroy harmful bacteria such as E. coli O157:H7 without significantly changing milk's nutritional value. Pasteurization can also prevent other contagious diseases such as salmonellosis, campylobacteriosis, listeriosis, yersiniosis, and others that can be spread by bacteria in milk. All milk shipped between states is required by law to be pasteurized.
Are you trying to clamp down on all raw milk sales? It seems like you are trying to take away our food source, our ability to choose to drink raw milk.
- Like Mr. Hartmann, we wholeheartedly endorse the value of consumer choice.
- Statutes governing the sale of raw milk were written in 1949. However, in this case, human disease – in the form of E. coli O157:H7 infection – has been clearly linked with consumption of milk from Mr. Hartmann’s farm
- Generally, the risk of getting a disease like E. coli O157:H7 is small, but the consequences can be very great. When one consumes raw milk, the risk of getting a disease like E. coli O157:H7 is much, much greater.
- At best, an E. coli infection can cause up to two weeks of bloody diarrhea.
- At worst, in very young children, it can lead to potentially fatal kidney failure.
- We nonetheless support the rights of consumers who wish to assume that risk – IF they do so knowingly.
- When raw milk is distributed beyond the premises of the farm where it was produced, you drastically increase the likelihood that consumers will purchase the product without knowing that they are in fact getting raw milk – or what the risks involved might be.
That’s why current law forbids the distribution of raw milk beyond the location where it was produced.
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