Raw milk may contain harmful germs that pose significant health risks to humans. The process of pasteurization is specifically crafted to effectively eliminate the bacteria Mycobacterium tuberculosis and Coxiella burnetii. C. burnetii, an obligate intracellular gram-negative bacterium, is highly infectious and shows resistance to harsh environmental conditions, including physical and chemical stresses.
This bacterium undergoes a two-stage growth process, resulting in two distinct morphological types known as the large-cell variant (LCV) and the small-cell variant (SCV). The resilient SCV morphotype enables C. burnetii to remain stable in the environment and resistant to various physicochemical stresses, such as disinfectants, dehydration, irradiation, and osmosis. Consequently, the bacterium can persist for extended periods in dairy and meat products, as well as in aborted fetuses, manure, wool, animal feed, equipment, and clothing.
C. burnetii is recognized as the causative agent of Q fever, initially identified in 1935 as an occupational disease among abattoir workers in Australia and as a tick-transmitted disease in the United States. Naturally infecting animals like goats, sheep, and cattle, C. burnetii is found in birth products (placenta, amniotic fluid), urine, feces, and milk of infected animals. Shedding of C. burnetii can endure for several months to 1-2 years in vaginal mucus, feces, and milk after the initial infection. Human infection can occur through the inhalation of dust contaminated by infected animal feces, urine, milk, and birth products.
Raw milk is considered the primary source of C. burnetii among animal-origin food products. The bacterium is excreted in the milk of infected animals, including cattle, sheep, and goats, regardless of whether they exhibit clinical signs of infection, and can persist for varying periods during lactation. Following World War II, a notable increase in Q fever and serological conversion was observed in Europe and North America, particularly in regions where the consumption of raw milk and its products was prevalent.
Q Fever from Raw Milk
