Listeria is a bacteria found in raw milk (milk that has not been pasteurized). It is actually everywhere: in the soil, on the floor of the barn, and in the water. Because it is ubiquitous, meat, milk, cheese, and even vegetables can easily become contaminated.
Listeria poses a specific risk to pregnant women. If exposed to listeria, a pregnant woman is 20 times more likely to become ill (people with weakened immune systems, such as a premature baby, the elderly, or those with HIV, are also at increased risk). In the United States, pregnant women make up about 30% of cases of listeria infections.
A pregnant woman with listeria may develop a flu-like illness or she may have no symptoms at all. However, listeria can impact her pregnancy even if a woman doesn’t feel very ill. Listeria in pregnancy can cause to miscarriage, stillbirth, premature delivery, and infection of the newborn.
Illness and deaths from listeria infectious acquired from raw milk are well reported in the medical literature. In 2007 five people were sickened with listeria from drinking milk purchased from Whittier farms, a family owned dairy in Massachusetts. Of the five who fell ill, three were men between the ages of 75 and 87 and two were pregnant women. All three men died and and the two pregnant women had serious complications: one delivered her baby prematurely, her placenta tested positive for listeria, and the other suffered a stillbirth at 37 weeks – an autopsy indicated her baby had been infected with listeria.
The FDA is now inspecting cheese making facilities for listeria (both companies that use unpasteurized milk and those that use pasteurized milk). With products made on a farm (for example, cheese or milk sold in pails) there are 2 sources of contamination, the milk that is being used but also the environment where product is made/bottled/packaged. Many artisan cheese makers work on their farm. If they are not obsessive about cleaning, sterilization, and making sure no one is tracking in dirt from the farm, the cheese can become contaminated. As many artisan cheeses age > 60 days that is a lot of opportunity for contamination if there isn’t obsessive attention to cleanliness.
To avoid listeria infection in pregnancy the CDC recommends the following:
- Avoid raw milk and any products, such as cheese or butter, made with raw milk. Soft cheeses post a greater risk, because they are low acidity and have a lot of moisture, so it is easier for the bacteria to grow during the aging process.
- Thoroughly cook all meat. Use a meat thermometer: 1 out of 4 hamburgers turns brown before it reaches a safe internal temperature! Click here for a temperature refresher courtesy of the USDA.
- Wash all vegetables thoroughly before eating.
- Don’t eat deli meats. They can become contaminated with listeria after processing. If you just HAVE to eat something from the deli, make sure the meat is heated until it is steaming hot, although it’s really best to skip the deli.
- Treat hot dogs like deli meat. Heat until are steaming hot before consuming.
- Do not eat refrigerated smoked fish such as salmon, trout or mackerel (also can become contaminated after processing).
Remember, this blog is not direct medical advice.