PARA Report

National Johne's Working Group at annual meeting of U.S. Animal Health Association

National Johne's Working Group (NJWG) -- October 20,2000

This year marked a partial return to its roots for the NJWG, with two significant presentations: one discussing Mycobacterium avium subspecies paratuberculosis (MAP) as a potential cause of Crohn's disease in humans; the other an update on pasteurization studies.

Presentation by Dr. Michael Collins

Dr. Michael Collins delivered a summary of the highlights a paper to be published in the December issue of the Journal of Clinical Microbiology entitled "Results of multiple diagnostic tests for Mycobacterium avium subsp. paratuberculosis in patients with inflammatory bowel disease and controls."

Dr. Collins, together with ten other researchers, had completed a study that applied multiple diagnostic tests for Mycobacterium avium subspecies paratuberculosis to humans having some form of inflammatory bowel disease.

The researchers tested patients using six different diagnostic assays, normally used for testing animals, adapted to human subjects.

When the data were in, the researchers concluded that there was an "association" between MAP and Crohn's disease. As Dr. Collins explained, "Association ... means that we found these two things occurring simultaneously beyond what we would by chance. This is not happening by accident. These two are occurring at the same time -- inflammatory bowel disease and paratuberculosis or evidence of it -- way beyond chance."

"Association," explained Dr. Collins, "does not prove causation." But as he pointed out, the definitive study to prove causation would require inoculating 100 children with the MAP organism and studying them -- an unthinkable scenario.

But with the data from this study, the researchers agreed that the "preponderance of evidence suggests involvement of a mycobacterial agent in inflammatory bowel disease."

"As food for thought," concluded Dr. Collins, "I think we have to put this in the context of what we know about pathogens in the field of mycobacteria. We have essentially a list of pathogenic species, all of which are known to cross freely between animals and humans:

• Tuberculosis, a known human pathogen, we are now isolating from elephants on a routine basis.
  
  
• M. bovis -- well-known to cross the other way -- it prefers to be in animals, but freely crosses to humans.
  
  
• Mycobacterium leprae -- it's natural host we think is armadillos. They are regularly infected, but it's a disease of humans.
  
  
• Mycobacterium avium. Lower virulence, well-known as a cause of tuberculosis in chickens, but now with the AIDS epidemic we know it can also infect humans.
  
  

"So when we get down to paratuberculosis, technically a subspecies of M. avium, and we know that it's an animal pathogen, the leap to the assumption that it might infect humans is not really such a great one."

Full text and audio of Dr. Collins' presentation

Abstract of paper

Presentation by Dr. Judy Stabel

Dr. Stabel is the lead scientist of the Johne's Disease Project at USDA/ARS Ames, Iowa center.

Of the topics that Dr. Stabel covered, of interest to Crohn's sufferers are the updates on current and future pasteurization studies around the world -- UK, USA, New Zealand, Australia, Germany and the Netherlands:

• The report from the UK Food Standards Agency Preliminary results from the National Study on the microbiological quality and heat processing of cow's milk: Mycobacterium avium subsp. paratuberculosis
  
  
• The Food Standards Agency's press release Agency plans action on milk bug
  
  
• Excerpt from IDFA Report -- Task force on M. paratuberculosis:

  USA: A trial of pasteurization of milk, cheeses, ice cream and other dairy products, using lab-scale and commercial pasturizing equipment. Study set to begin November 2000.

  New Zealand: Completed first series of experiments using pilot-scale pasteurizer. Results show that "laboratory simulations can seriously underestimate the effectiveness of commercial pasteurization."

  Australia: Tests under way of commercial pasteurizer. Researchers endeavoring to simulate real-world conditions accurately.

  Germany: Researchers used pilot plant pasteurizer. Conclusion: MAP survives even the upper limit of legal pasteurization temperature and time standards (72-75ºC, 15-30 sec.)

  The Netherlands: Cooperating with Belgium and Great Britain in experiments. One goal: to find "natural" heat resistance of MAP by using cells from naturally contaminated milk.

  IFDA Summary: HTST (the most common method) pasteurization produces "significant killing" of MAP. (PARA's note: But not complete killing.)