Most dairy farmers have long recognized that feeding raw milk to calves is not exempt of health risks. Of the U.S. dairy farms only 25.6 percent feed raw milk to their calves (APHIS 2007). Dairies with more than 500 cows are rapidly adopting pasteurization with 30.7 percent of them already doing it. The reason has been the understanding of the role pasteurization played in history as a process to increase milk safety both in cattle and humans.
In the late 1800 tuberculosis in the U.S. decimated both cattle and human populations. At the time 70 to 90 percent of urban inhabitants were infected, and almost 80 percent of those died from the disease. Unpasteurized cow’s milk was a very common cause of tuberculosis, typhoid fever and salmonellosis. Unpasteurized cow’s milk caused nearly 25 percent percent of all food-borne outbreaks during that time. Public outcry demanded solutions to the high children mortality. In 1882 commercial pasteurizers were developed with the first U.S. milk pasteurizing plant opening at Sheffield Farms Dairy in New Jersey in 1891. In 1892 the “Pasteurized Milk Laboratory”, funded by the Straus family, opened in New York offering free of charge “purified milk” (pasteurized) to indigent mothers. In 1897, encouraged by the results obtained in New York, the U.S. Health Department set chemical milk standards, and required milk shop dealers to obtain permits. Chicago became the first major American city in 1908 to pass a law that required commercial milk pasteurization. . Initially introduced to prolong milk shelf life, pasteurization led to the full control of bovine tuberculosis (TB) transmission to humans.
Scientists discovered later on, that the tuberculosis bacterium was not the only pathogen present in milk, and that it could contain other bacteria such as brucella, E. coli, salmonella, and listeria. Alice C. Evans (1881-1975) a USDA microbiologist discovered in 1918 that brucella, the bacterium which caused “undulant fever”, the disease with which she was personally affected, could be found in milk.
Other bacteria sometimes found in raw milk have resulted in recent outbreaks. In a recent E. coli outbreak for example which occurred in Tennessee in November 2013, nine children became ill after drinking raw milk. Five of the nine children, all younger than seven, required hospitalization, and three developed a severe kidney problem known as hemolytic uremic syndrome. Listeria monocytogenes is less frequently found compared to other bacteria however it is feared for its relatively high fatality rate.