esults to argue against committing serious research dollars to investigating the seemingly well-reasoned hypothesis that a bacterium known to cause disease in cattle -- that is shed live in their milk -- can be transmitted to and cause a similar disease in humans.
But without well-funded research, there are no definitive answers to these vexing questions: Does Mp cause or contribute to Crohn's disease in humans? Does Mp survive the pasteurization process? Is it currently in the retail milk supply? Are our children at risk? And if the answer to any of these questions is even possibly yes, why isn't the American public aware that this is indeed a concern?
Estimates are that between 500,000 and 1 million people in the U.S. have Crohn's disease, and it is spreading rapidly. Approximately 55 Americans, mostly between the ages of 15 and 25, will be diagnosed with this incurable disease every day, and at least half of Crohn's patients will require surgery. All will suffer, mostly in silence due to the embarrassing nature of the symptoms, without any awareness that there may be a connection between their illness and the consumption of dairy products.
Researchers investigating the possibility that Mp causes Crohn's suggest that people may be infected with the organism at a young age, when milk consumption is high. Because it is a known to be a slow-growing organism that probably requires a trigger to cause symptoms -- such as the hormonal changes of adolescence -- people do not come down with the disease until later in life. Further, they believe that there is a genetic predisposition, as the disease has a tendency to run in families. They are quick to point out, however, that even the most infectious agents, such as tuberculosis, only causes disease in one out of approximately 300 people who are exposed to it. So exposure to the bacterium does not necessarily equate with contracting the disease. But despite all the mitigating circumstances, a handful of respected researchers around the world suspect Mp is the main culprit in causing Crohn's disease.
"Crohn's disease has a very spotty distribution in the world," notes Dr. Walter Thayer, an expert on the disease at Rhode Island Hospital who worked with Chiodini to culture Mp from Crohn's patients. "But it's seen only in milk-drinking areas -- Australia, southern Africa, Europe, the United States, Canada, New Zealand. Interestingly, it's not seen in India, where they do drink milk, but they boil it first.
"The other thing, Crohn's disease wasn't really known until the '20s. And there were only a few cases in the literature. Now it's a very common disease. What has happened to dairying in that time? Do you get milk from your local dairy? No. You get it from big conglomerates that buy from local dairies and pool all the milk. I think this is possibly the reason the disease has spread so quickly."
Just as Crohn's disease is increasing in the human population, Johne's disease is spreading among dairy cattle. According to a National Animal Health Monitoring System study conducted in 1996 for the United States Department of Agriculture (USDA), an estimated 22 percent of U.S. dairies are infected with the Johne's organism. Larger herds are more likely to be infected -- about 40 percent of the herds with more than 300 cows had at least a 10 percent infection rate.
According to the same study -- despite both its having been identified more than a hundred years ago and the increasing incidence of the disease in dairy herds, which is costing the industry an estimated $1.5 billion a year -- 45 percent of dairy producers are either unaware of Johne's disease or know little about it. This is perhaps due to the fact that between 1992 and 1996, less than 1 percent of the USDA's National Research Initiative Competitive Grants funding was allocated to Johne's research and/or education. Regardless of any human health consequences this organism may cause, clearly a problem has been allowed to fester.
"It's one of the most economically significant infectious diseases," says Collins about the prevalence