Certain modern trends can sometimes threaten the progress that science has brought us. This is the case with the recent fad of drinking raw milk, a practice that puts food safety at risk and which experts and health authorities have warned against. And it’s an opportune moment to remember the pioneer to whom we owe safe milk, American microbiologist Alice Catherine Evans, whose landmark discovery found acceptance despite resistance from those who were suspicious of a woman without a doctorate or medical degree.
Evans (January 29, 1881 – September 5, 1975) lived at a time when microbiology was in its infancy. In 1864, French biologist and chemist Louis Pasteur had described his system for preserving liquids by heat —pasteurization— but at that time it was applied to wine or beer, not to milk, which was believed to be safe as long as it was not contaminated. However, the speed with which milk spoiled made it a very dangerous food. In the past, dairy farms were sometimes located in the cities to reduce the time between production and consumption, but the disappearance of these establishments led in some cases to the use of adulterants to disguise the spoilage, such as bicarbonate, sugar, molasses or even chalk.
At that time, knowledge of the diseases associated with raw milk was still very limited. It was known that a bacterium, Bacillus abortus, spread between animals, causing spontaneous abortions. In humans, Malta fever was caused by Micrococcus melitensis, found in the milk of Maltese goats. However, no one had ever thought of linking these two ailments, until a bacteriologist from the US Department of Agriculture (USDA), dedicated to investigating the bacterial flora in milk, tied up the loose ends.
From rural teacher to bacteriologist
Evans’ journey to the laboratory was hampered by her lack of money to pay for university studies. She was introduced to the study of natural sciences through a course that Cornell University offered free of charge to rural teachers, her occupation at the time. Fascinated by biology, she took advantage of an opportunity that Cornell offered to study agriculture also free of charge, and which allowed her to select a scientific specialty, bacteriology. But when the time came to choose between a doctorate or a research position in the USDA’s Dairy Division, she opted for the latter.
Evans discovered that B. abortus was present in raw milk on a regular basis, contrary to the prevailing view that this product was safe. By studying and comparing this microbe to M. melitensis in goats, she noted that they were almost identical. In 1917 she presented her findings to the American Society of Bacteriologists, and the following year she published them in the Journal of Infectious Diseases. Evans’ claim that normal raw milk could cause disease in humans, and that this risk was eliminated by pasteurization, was met with disbelief by scientists, doctors and veterinarians; in the case of farmers, she was even falsely accused of having a pecuniary interest in pasteurization equipment.
Trailblazing and pugnacious
Evans’ work was corroborated by other experts, and in 1920 a new genus, Brucella, was proposed to encompass the former B. abortus and M. melitensis. The latter, renamed Brucella melitensis, ended up infecting the researcher herself in 1922, and would impair her health for more than 20 years. However, there were still those who rejected her conclusions: the renowned doctor and researcher Theobald Smith was reluctant to believe that brucellosis affected humans. “He was not accustomed to considering a scientific idea proposed by a woman,” Evans would write about him. Years later, the two would work together on a committee on communicable diseases causing spontaneous abortions.
Recognition of Evans’ findings led to the imposition of milk pasteurization beginning in the 1930s, and resulted in the researcher becoming the first female president of the Society of American Bacteriologists (now the American Society for Microbiology) in 1928. Evans was trailblazing and pugnacious by nature: in high school she played basketball, and she flew in an airplane a year after Lindbergh’s famous Atlantic crossing. In 1966, at age 85, she denounced as unconstitutional the regulation that required the disclosure of communist affiliations in the application for public health insurance, Medicare. The following year, this requirement was withdrawn.