I'm sure the irony is quite unintentional. Nonetheless, I couldn't help but chuckle at the notice for the International Raw Milk Symposium: From Production to Consumption taking place in Toronto on Jan. 31. You see, "consumption" is a commonly used term for tuberculosis, and pasteurization of milk was mandated to help fight it and other diseases that can be transmitted from animals to people.
These diseases, also called zoonotic diseases, have caused enormous human suffering through the centuries. Although not all tuberculosis was transmitted through cattle, historically about 10 per cent of human tuberculosis cases were related to cattle and raw milk consumption via zoonotic tuberculosis and brucellosis.
Zoonotic diseases pose an enormous and growing challenge to public health. It's estimated that 60 per cent of human pathogens - and more than 75 per cent of new, emerging infectious diseases of humans - come from animals or their products. Zoonotic food-borne diseases will affect one in four individuals annually in developed countries.
Pasteurization is a process that heats a product - milk in this case - for a predetermined time at a predetermined temperature to kill bacteria, and pasteurization of milk has been mandatory in Ontario since 1938. It is also used for other products, such as cheese, cider and fruit juices.
So with a safe alternative available, and in fact mandated by law, why would anyone want to drink raw milk? Proponents cite a number of potential health benefits, such as decreased risk of lactose intolerance and allergic reactions. They also say that pasteurized milk is "clean" but lacks natural, beneficial milk components that are lost through the process. However, these claims are generally not substantiated by the scientific literature.
While we are fortunate that bovine tuberculosis has been eradicated in domestic cattle in Canada, there are still public-health risks associated with the consumption of raw milk. These risks include campylobacter, salmonella, listeria, E. coli O157 and others. And these risks are not uncommon - as seen by the current peanut butter recall here and in the United States, and the Canadian listeriosis outbreak of late 2008.
The opportunities to pass disease from cattle to humans are many. The cattle may directly shed bacteria in the milk or, more commonly, in their feces. Even in a clean environment, there is the potential for cattle udders to become contaminated with feces, which can result in contaminated milk.
Of particular concern is that these bacteria may be present in cattle intestinal tracts or milk without causing apparent disease in the cattle and are found in cattle under a variety of farm management types. For instance, E. coli O157:H7, which can cause serious and even fatal disease in humans, is carried in the feces of healthy cattle of all ages and from cattle on a variety of diets, including pasture and hay-fed.
While unpasteurized products pose health risks to all, pregnant women face additional risks from the consumption of raw milk. For example, listeria can cause miscarriages or fetal death.
Dairy farmers strive to produce a safe and nutritious product for consumption by all Canadians, particularly children. Pasteurization is an important part of the milk production system and is performed for the safety of the public.
Dr. Jan Sargeant, a veterinarian, holds a national applied public health chair from the Canadian Institutes of Health. She is director of the Centre for Public Health and Zoonoses at the Ontario Veterinary College, University of Guelph.
