Health & Medicine

The Agony and Mystery of Crohn's Disease

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THE CAPITAL ã ANNAPOLIS, MARYLAND ã HOMETOWNANNAPOLIS.COM ã CAPITALONLINE.COM Pathogens & People: Agony and mystery of Crohn's Disease By EDWARD McSWEEGAN, For The Capital Published January 04, 2009 About 75 years ago, an American physician described a gastrointestinal disorder that was similar to intestinal tuberculosis. Today, that disorder is known as Crohn's disease. Unfortunately, after 75 years, there are still many unanswered questions about this disease, including the cause. There also
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  THE CAPITAL ã ANNAPOLIS, MARYLAND ã HOMETOWNANNAPOLIS.COM ãCAPITALONLINE.COM Pathogens & People: Agony and mystery of Crohn's Disease By EDWARD McSWEEGAN, For The CapitalPublished January 04, 2009About 75 years ago, an American physician described a gastrointestinal disorder that was similar to intestinal tuberculosis. Today, that disorder is known as Crohn's disease. Unfortunately, after 75 years, there are still many unanswered questions about this disease, including the cause. Therealso is no cure and no truly effective therapy.What Dr. Burrill Crohn described in 1932 is a chronic inflammation of the intestinal tract.Common symptoms include abdominal pain, persistent diarrhea, weight loss and malnutrition,and occasional bleeding and anemia. It is a painful, unpredictable condition that can makenormal work schedules and social activities difficult. The Centers for Disease Control andPrevention estimates there may be 500,000 people in the United States with Crohn's disease.What causes it? It was thought to be an immune disorder, so steroids and other anti-inflammationand immunosuppressive agents have been prescribed, along with anti-diarrheal drugs. In severecases, surgeons can remove ulcerated or infected parts of the affected intestine.Interestingly, humans are not the only species to suffer from such a depressing and disastrousdisorder. Cattle also suffer from a Crohn's-like illness called Johne's disease. This bovine illnessis an infection caused by Mycobacterium avium paratuberculosis , a bacterial cousin of thetuberculosis bug.Could the MAP bacteria also cause Crohn's disease in people? It's a good bet, but showingcausality is proving to be difficult. Still, if you can identify a cause, you can design a cure, andMAP seems like a good place to start.How would a person acquire bacteria that are normally associated with a livestock infection? Notmany people spend time around cattle herds, but it is possible the MAP bacteria may betransmitted through contaminated meat and dairy products. MAP frequently survives standardmilk pasteurization, for example. Alternatively, it could be transmitted through soil and water contaminated by livestock waste.The majority of patients with Crohn's disease usually test positive for the presence of MAP. Yet,ranchers and dairy farmers - who might be expected to have greater exposure to MAP - do nothave higher rates of Crohn's disease. So perhaps there is also a degree of genetic susceptibility insome people that allows MAP exposure to progress to active infection and overt disease.If Crohn's is caused by MAP bacteria it should be treatable with antibiotics. Indeed, someCrohn's disease patients readily respond to antibiotic treatments. For those who do not respond, itmay be a matter of finding the most effective combination of antibiotics and the most effectivelength of treatment time. So far, it's been mostly guesswork. Common anti-TB drugs were used  until it was discovered that MAP is resistant to them. Since then, a cocktail of three antibiotics -rifabutin, clarithro-mycin and clofazimine - have been used to treat patients in the U.S. andAustralia.A two-year study of 213 Crohn's disease patients in Australia ended in 2007. The study used thethree antibiotics listed above, but the results only seemed to add to the confusion and controversyabout MAP as a definitive cause of Crohn's. In medical journals, the study was called flawed  because the researchers apparently used suboptimal antibiotic doses and failed to detect MAP in patients before or after treatment. To be fair, the gastrointestinal tract is a hostile environment toresearchers trying to study drug effects on a single type of bacteria. The human intestinal tractcontains numerous chemical and physical barriers; has a rapid turnover of cells and activelyempties the intestinal contents; contains acids, bile and digestive enzymes; and is home totrillions of other bacteria that normally live there. MAP is a very small target in a very crowded,chaotic environment.Still, research and treatment trials continue. Earlier this year, the American Academy of Microbiology released a report on expert recommendations for more research on MAP andCrohn's disease. The report laid out a compelling case for MAP's involvement in Crohn's disease,and recommended more laboratory research on diagnosing MAP and measuring the bacteria'ssusceptibility to various antibiotics. Two other important questions that need answers are: how isthe disease transmitted and who is susceptible to MAP and subsequent disease? Commenting onthe report, study director Carol Nacy of Sequella Inc. in Rockville said, We still have a longway to go. For more information about Crohn's disease, see the Crohn's and Colitis Foundation of Americaatwww.ccfa.org.For ongoing treatment trials for Crohn's patients, searchwww.clinicaltrials.gov.Dr. Edward McSweegan has a Ph.D. in microbiology and lives in Crofton. He works on andwrites about infectious disease issues. He may be contacted atmcsweegan@nasw.org.
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