Preliminary results from two ongoing Ontario studies suggest that a bacterium responsible for a widespread disease in cattle, survives pasteurization. Researchers have suspected for almost twenty years that a bacterium responsible for causing a gastrointestinal disease in cattle may also play a major role in the development of Crohn's disease in humans. The problem to this day remains to prove the theory. The bacterium may be transmitted from animals to humans through pasteurized milk. Public Health authorities are increasingly preoccupied by the possibility of such a link. The dairy industry is facing scientific evidence that is controversial and because uncertainties abound, there is no consensus to know whether a causal link in fact exists between the bacterium and the human disease. Nonetheless, a mere suggestion that milk may not be exempt from this bacterium represents a potential nightmare for marketing of this consumer food.
The Association of dairy producers in Ontario is financing two studies being carried out by the Department of Microbiology at Guelph University in Ontario. One study analyses samples of retail milk that have been injected with the bacterium "Mycobacterium avium subspecies paratuberculosis" or Map as it's known in the jargon of microbiology. The samples are then pasteurized in the lab. The second study consists of analyzing samples of commercially pasteurized milk. In both cases, they want to know whether the pasteurization process succeeds at killing the bacterium. Wes Lane, research director for the association, explains what prompted the dairy producers to finance such studies: "First of all, there is the economic impact of bovine paratuberculosis that is becoming progressively more common in dairy herds. And furthermore, the possibility that a link between milk and Crohn's disease is ever determined worries the Ontario dairy industry. It would be a catastrophe if the public lost confidence in their milk."
Wes Lane and Joseph Odumeru, microbiologist responsible for the studies, maintain that no test results are presently available. Even so, a document from Health Canada dated last December 14th makes mention of preliminary results. The document from the Food Risk Agency of Health Canada in fact indicates that milk samples from the two studies being performed at Guelph University, have tested positive for the presence of the bacterium Map. In what proportion is this bacterium present can only be determined by studies that are more extensive. Joseph Odumeru admits that this is a very delicate subject and that Guelph University has agreed to discuss the results with Ontario's dairy producers before making them public.
And if the final test results are positive that in fact the bacterium was present in milk? What would be the next step? Wes Lane doesn't want to anticipate what decisions would be taken at that moment. What is certain though is that the results would elicit much interest on the part of the dairy industry, but also on the part of the organization responsible for public health in this country, and that is Health Canada. Stacey Mantha, biologist at the Infectious Disease Branch of Health Canada, is well acquainted with the bacterium that is presently being studied most everywhere in the world. "I've participated in discussions where there was question of national investigation of retail milk, like the studies recently concluded in the UK (last year). For the moment though, nothing's in the works."
Tracking A Bacterium
Canada's not the first country to search for the presence of this germ in pasteurized milk. Since 1993, there have been seven major studies in Europe and in the United-States. Five of them reported that the bacterium survived pasteurization. Between 1990 and 1998, the American National Medical Library lists 27 research papers of international significance, on the possible link between Crohn's disease and MAP. These are investigations, which have generally arrived at contradictory results.
Health Canada has followed the studies for at least seven years. In 1994, the Food Risk Agency of Health Canada draws up an internal document stamped in English: "Protected, not for distribution". There is question of Mycobacterium paratuberculosis as agent responsible for Crohn's disease and milk as possible vector of transmission and cause for concern for public health. The following year, Agriculture and Agri-Food Canada, in conjunction with Cornell University in New-York State, mounts a study of non-pasteurized milk samples coming from southern Ontario, to try to detect the microorganism. Scientists do not detect the bacterium. At that time, methods for isolating and identifying this bacterium are not very sophisticated. Since 1997, American and European studies have proved that the bacterium can survive pasteurization.
Official results from the ongoing studies at Guelph University will be known later this year. We will then know if retail milk is free of the bacterium. The Ontario dairy industry would like to be free of this nagging issue. And with cause: 81% of dairy resources are situated in Ontario and Quebec. Canada's dairy industry ranks 3rd in importance in agriculture after cereals and red meat. In 1999, it was an industry worth 4 billion dollars.
Dr Jean Lachance, gastroenterologist at Sainte-Justine Hospital, says that there is no need for undue concern at this moment: "Each year I participate in many scientific conferences and this link between bacterium, pasteurized milk and Crohn's disease is far from unanimously accepted. Even if I had a young patient coming from a family where Crohn's disease already exists, I would certainly not advise him to stop drinking milk. Not at all." Are the dairy industry and the Ministry of Agriculture for Quebec (MAPAQ) worried about the presence of this bacterium in milk? The role of the Quebec Federation of dairy producers is similar to that of the Association of dairy producers of Ontario. Jean Vigneault, director of communications for the Federation, had few comments on the issue. "I must inform myself before answering on a subject that, for the moment, means nothing to me." Something that he did. He declares that the Federation will follow the problem closely. As for the Council for the Quebecs dairy industry, its main responsibility is the economic development of the industry. Its president, Claude Lambert, emphasizes that it's not up to the Council to set quality controls in order to certify that milk poses no danger to the consumer. The responsibility for those controls falls on the Ministries of Agriculture, both at the federal and at the provincial levels, through their inspection agencies. He confirms however, that whatever can impact negatively on the dairy industry concerns them. During the interview, Mr. Lambert acknowledges that it's the first time that he hears of a possible link between this cattle disease and Crohn's disease.
National Studies in the UK
On the government side, the inspection agency for the Ministry of Agriculture in Quebec (MAPAQ), is responsible for the inspection of milk and dairy products destined for sale inside Quebec. Michel Houle, operations advisor, keeps abreast of scientific research, however controversial, on the role that this bacterium may play in Crohn's disease. His department hasn't contemplated doing any studies to test for the bacterium in milk sold in Quebec. "We are waiting to see, in part, the final results of the British tests," said Michel Houle. Preliminary results from the national tests in the UK showed last autumn, that 3% of samples of commercially pasteurized milk, originating from approximately 800 British dairies, contained the bacterium. The Food Research Institute in the UK is analyzing the report and will present the final results at a conference later in the spring. In the meantime, the institute recommends that the public not change its milk consumption. Réjean Bouchard, president of Canada's dairy producers, asks himself: "To begin with, did the British dairies do their job well, according to regulations? I believe that in North America, we do better than over there."
If there's a risk that the bacterium that causes bovine paratuberculosis can find its way into milk destined for human consumption, we must try to control the disease in cattle. Michel Major, veterinary for the Ministry of Agriculture, is about to undertake an investigation of dairy herds in Quebec in order to learn how widespread bovine paratuberculosis has become at home. In the US, the Federal Bureau of Agriculture has disclosed that 41% of dairy herds of more than 300 animals were infected with paratuberculosis. Investigations in the Maritime Provinces in 1998, and in Ontario in 1999 give similar results. Michel Major states that in spite of differences in investigative methods from one area to another, "there is no reason to believe that our results will be very different from those found elsewhere in the world".
Living with Crohn's Disease
We still don't know what causes the disease that carries the name of the researcher who first identified it in 1932. We know that it's a chronic disease that can be devastating in its episodes of severe diarrhoea that lead to substantial weight loss. It attacks mostly the young in early adulthood and people after their sixties. Scientists seem convinced of one thing however: this disease is not "mono-factorial" which means that it is most probably caused by multiple factors. It is possible that it is triggered by an abnormal reaction to a bacterium or a virus. A reaction that could be triggered by a genetic predisposition, but that hypothesis has not been proved either.
Studies that could tell us how many people suffer from this disease in Canada are few in numbers and mostly regional. In 1994, a study in Manitoba revealed almost 200 cases of Crohn's disease per 100 000 population. This represents the highest incidence ever published in the world. In comparison, there are 60 cases per 100 000 population in the UK, 34 in Australia and 6 in Japan. The Canadian Crohn's/Colitis Foundation, in collaboration with researchers from every province, including Quebec, is presently establishing a registry for Crohn's patients. This registry will give a more accurate picture of the number of Canadians suffering from the disease.
The Foundation estimates that at this moment, there are app. 100 000 Canadians with inflammatory bowel disease. Gilles Demers is 20 years old when he's told that he suffers from Crohn's, a disease with no known cause and no known cure. "I cried all day when they announced the diagnosis", says this man from the Sherbrooke region, now 39 years old. Four surgeries performed in the early 80's have resulted in his having today only 2 meters of intestine instead of 6 meters. His inability to absorb nutrients properly necessitates his using a tube at night in order to feed himself. "The first 10 years were very hard", remembers Gilles, now married and father of two children. After periods of flares and then convalescence, he eventually has to stop working indefinitely. He's in remission now for the last 9 years and receives a disability pension from Quebec. Gilles' case is pretty severe. People with Crohn's disease can have symptoms that are less severe than Gilles' but all suffer a lifetime of flares and remissions.
Similarities with the bovine disease
American and British scientists wanted to establish a link between the bacterium that causes paratuberculosis in cattle and Crohn's disease in humans, precisely because the symptoms bear such striking similarities. Dairy cows or beef cattle present the following symptoms: severe inflammation of the intestinal wall and severe diarrhoea and weight loss. In 1984, the American microbiologist Rod Chiodini, then at the University of Connecticut, was the first to succeed in isolating the bacterium from the intestines of Crohn's patients. During this same period, Professor John Hermon-Taylor, chief of surgery at St George Hospital in London, discovers a DNA sequence unique to the bacterium that will facilitate identification of the bacterium in both Crohn's tissue and in milk. "Because after many discussions, John and I arrived at the conclusion that milk would be the most plausible carrier between animals and humans, but there can also be water and ground meat", remarks Rod Chiodini during the interview. For John Hermon-Taylor, after 20 years of research, "there is no more doubt, this bacterium that causes a disease in cattle also plays a role in Crohn's disease. Let's at least assure ourselves that milk is safe", he states during a telephone conversation. Herbert Van Kruiningen, professor of pathobiology at the University of Connecticut, is an old colleague of Rod Chiodini. "We were on a good track there during the 80's but as for me, the scientific community failed to repeat the experiment in a satisfactory way" he concludes when contacted on the subject. For him, science was not able to prove that there is a common cause between the bovine disease and the human disease, in spite of apparent similarities between the two diseases.
This debate, which is not settled among the scientific community, has nonetheless caught the attention of Nicole Fréchette. Her son developed Crohn's disease just as he was entering university. Nicole, originally from Quebec, has been living in British Columbia for many years. Having made a career in nursing, she was able to navigate the scientific documents with a certain ease. It's during this search that she discovered the Internet site PARA (Paratuberculosis Awareness and Research Association).
PARA is an international organization that was established in 1997 by 2 American mothers, one from Ohio and the other from Florida. These mothers share a common bond in both having a child who suffers from Crohn's disease. PARA is actively lobbying the diverse government agencies in the US for funds to be earmarked for research into an infectious aetiology of Crohn's disease and for testing of retail milk. Last March 13, Cheryl Miller, co-president of PARA, addressed the American Congress to request allocation of 500 million US, the amount required to mount extensive research on this bacterium and on retail milk. It will be next September before allocation of research funds are announced by Congress but nonetheless, members of Congress have publicly indicated that they will give their request very serious consideration.