<http://www.sciencedaily.com/releases/2008/08/080807144309.htm>
Pathogen That Causes Disease In Cattle Also Associated With Crohn's Disease
ScienceDaily (Aug. 11, 2008) — People with Crohn's disease (CD) are
seven-fold more likely to have in their gut tissues the bacterium that
causes a digestive-tract disease in cattle called Johne's disease. The
role this bacterium may or may not play in causing CD is a top research
priority, according to a new report released by the American Academy of
Microbiology.
The reports points out that the cause of CD is unknown, and the possible
role of this bacterium—which could conceivably be passed up the food chain
to people—has received too little attention from the research community.
The report, Mycobacterium avium paratuberculosis: Incidental Human
Pathogen or Public Health Threat?, summarizes conclusions and
recommendations from a colloquium convened by the American Academy of
Microbiology in June 2007 that brought together experts in microbiology,
medicine, veterinary pathology, epidemiology, infectious diseases, and
food safety. Colloquium participants described the state of knowledge
about the relationship between Mycobacterium avium subspecies
paratuberculosis (MAP) and CD and developed a research agenda to move the
field forward.
Scientists largely agree that multiple factors cause CD, including an
environmental stimulus, a genetic propensity, and an overactive
inflammatory and immune system triggered by an unknown event. There is
mounting evidence that the unknown trigger may be infectious in origin,
with several bacteria currently under consideration. "This complicated
network of causation has confounded efforts to understand CD, says Carol
Nacy, Ph.D., CEO of Sequella, Inc., who chaired the colloquium and is the
report's co-author. "MAP may be one of the causes of CD," Nacy adds,
"since, among other things, multiple studies identified the pathogen in
tissues of CD patients. Treating some of these patients with antibiotics
that target Mycobacteria provided relief from symptoms."
Johne's disease is a severe and fatal bacterial infection that strikes
cattle, sheep, and other livestock. MAP has long been identified as the
cause of Johne's disease. Despite efforts to limit the spread of MAP,
roughly 68% of cattle herds in this country are infected, meaning one or
more animals in the herd carry the bacterium and may develop Johne's
disease or spread the infection to other animals. MAP has been found in
some dairy products—milk and cheese—and beef on supermarket shelves.
The critical steps for research now, according to the report, are to
determine whether humans are exposed and infected with MAP by eating
infected meat and dairy products and whether MAP causes or incites CD or
whether it is only incidentally present in those afflicted with the
disease. The prospect that MAP could play a role in the incitement or
development of CD is a sobering one, and, once the situation becomes
clearer through research, there could be important changes in store for
agriculture, food safety, and public health. It is in the best interest of
the public that the possible connection between MAP and CD be explored
exhaustively, according to the report.
The research agenda, however, is seriously hampered by the lack of
reliable methods for isolating and indentifying MAP and for diagnosing
people with MAP infection. Public health laboratories and U.S. Centers for
Disease Control and Prevention laboratories have made it clear they cannot
grow MAP in the laboratory—an inability that hinders diagnosis and
screening. The report recommends establishment of a task force to develop
a specific road map for improved methods for MAP detection and diagnosis.
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