WSU researcher finds possible link between cattle, human disease - NBC Right Now/KNDO/KNDU Tri-Cities, Yakima, WA |

WSU researcher finds possible link between cattle, human diseases

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PULLMAN, WA - Washington State University Professor, William C. Davis, and his collaborators published a case report last week that provides more evidence that two gastrointestinal diseases, one in cattle the other in people, may be linked.

Davis is an immunologist in the Department of Veterinary Microbiology and Pathology in the WSU College of Veterinary Medicine.  He explains that Johne’s disease, (pronounced YO-knees disease) is a major animal disease problem worldwide. It is caused by a microorganism known as Mycobacterium avium paratuberculosis, or MAP for short. 

MAP infections result in an inflammation of the lining of the bowel leading to severe damages in the gastrointestinal tract.  Once the process begins, the animal can no longer absorb required nutrients, develops severe diarrhea, loses weight, drops milk production, and eventually dies.

He also says humans can suffer a suspiciously similar disease known as Crohn’s disease that has been linked to MAP infections in some studies.  Estimates are that up to 1.4 million people in the U.S. suffer with Crohn’s disease, costing more than $1.7 billion in healthcare costs annually. 

Here too, the intestine is inflamed resulting in severe diarrhea, excessive weight loss, debilitating abdominal pain, rectal bleeding, bowel obstruction, fistulas, and abscesses. About half of Crohn’s patients require surgery to remove a portion of their inflamed intestine.  Each day, about 55 people between the ages of 15 and 25 are diagnosed with Crohn’s disease in the U.S.

“MAP was initially theorized to cause Crohn’s disease in 1913 because of the similarities between the intestinal inflammation seen in cattle and humans,” explained Davis.  “It wasn’t until the mid-1980s when MAP was successfully isolated from three patients with Crohn’s disease that the idea gained more traction.”

Doubt quickly arose in the medical community as to whether MAP actually was the causative agent of Crohn’s. Investigators were unable to consistently demonstrate the presence of MAP in Crohn’s patients.  Other doctors isolated MAP alive and well in otherwise healthy subjects and some patients with other diseases.

A lack of definitive proof has resulted in a continued reluctance to accept that MAP is a zoonotic pathogen, meaning it is one that causes disease in both animals and humans.

Ongoing studies in Davis’ laboratory in Pullman, Wash., and collaborative studies with investigators in India may now reveal why it has been so difficult to show MAP is the causative agent of Crohn’s disease, in at least some patients.

A survey of 42,400 subjects in India was recently undertaken.  The subjects had a variety of diseases, including subjects with the clinical features of Crohn’s disease and subjects with no apparent health problems. The survey found that humans, regardless of health status, are susceptible to MAP infection.

Davis’ theory linking Crohn’s disease to MAP infections in humans, has driven him to devote a significant part of his career to the development of a vaccine to remove MAP from cattle, and thus from the food supply and the environment. 

Regardless of whether or not MAP is causative, “We’re making significant progress on a vaccine,” explained Davis.  A cattle vaccine provides the greatest promise for controlling Johne’s disease and benefitting cattle, regardless of the uncertainty surrounding the associations to human Crohn’s disease.

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