Johne�s Disease & Human Health
Dr. Clell V. Bagley, D.V.M.
USU Extension Veterinarian
Below is information abstracted from two articles relating to this disease and human health. It is important for dairy producers to be aware of this concern and consider the implications for their products. There has been important and very interesting progress in research efforts for control of JD. New tools will soon be available to enable more effective control of this disease in cattle. Watch for a summary of those new tools in the next Dairy Newsletter.
Johne�s-Crohn�s link gains ground
More refined tests for diagnosing Johne�s disease in cattle � a disease that causes animal suffering and costs U.S. dairy producers more than $200 million a year � appear to be on the way as the result of a newly completed genome map for the organism that causes the disease. It is a development that will help battle the devastation of Johne�s disease, while also advancing knowledge about what scientists increasingly believe could be a public health threat from the causative organism, Mycobacterium avium paratuberculosis (MAP).
While the connection has yet to be proven, after years of research, scientists are, with increasing frequency, uncovering tantalizing circumstantial evidence that the organism that causes Johne�s disease in cattle may play some role in Crohn�s disease, a complex, chronic and disabling inflammatory bowel disease in humans. Both Johne�s in cattle and Crohn�s in humans are increasing worldwide in all industrialized countries, scientists reported. Several countries have initiated Johne�s control programs.
News of the completed MAP genome sequence came just as two other key studies heightened concern about the MAP organism�s role in public health.
One study, conducted by the Marshfield Clinic in Marshfield, Wis., found viable MAP organisms in samples of pasteurized retail milk in California, Minnesota and Wisconsin � all among the nation�s top five dairy states.
The second study, conducted by a University of Central Florida research team, was reported a year ago in the British medical journal Lancet. It reported the team�s finding of viable MAP in blood of 50% of the Crohn�s disease patients sampled for the organism. The majority of these patients lived in Florida.
The Florida team, led by Dr. Saleh Naser, had earlier found MAP in the breast milk of three Crohn�s patients, as reported in the American Journal of Gastroenterology in 2000. Their research is continuing and is among a suite of projects on MAP, funded nationwide by the National Institutes of Health.
For the first time, the newly reported genome map identifies gene sequences unique to MAP, a breakthrough that allows more specific tests for the disease. The work, led by Dr. Vivek Kapur was completed through a USDA grant. The team already has developed a commercial test that will identify MAP in both fecal samples and milk.
Kapur said, �There is increasing evidence that MAP is present in a certain subset of Crohn�s patients. It is identifiable in tissue or blood of those patients.� Kapur believes �an association� between MAP and Crohn�s disease rather than �a causal relationship� has been proven. He describes Crohn�s as a complex autoimmune disease.
Naser concluded, �in short, for somebody to develop Crohn�s disease, the subject must be genetically or immunologically susceptible and exposed to MAP through contamination of food or drinks.� Fortunately, not everyone exposed to MAP is at risk of contracting disease.
(Feedstuffs, September 19, 2005; pp 1 & 32)
Marshfield study startles vet community
The Marshfield Clinic retail milk study published this spring in the Journal of Food Protection startled the veterinary community when preliminary findings were first reported last fall at the U.S. Animal Health Assn.�s annual meeting.
In the study, a research team from the Marshfield Clinic in Wisconsin, led by Dr. Jay Ellingson, reported finding viable Mycobacterium avium paratuberculosis (MAP) present in 2.8% of milk samples taken directly from retail grocery stores in three of the nation�s five largest dairy states.
The study also found remnant DNA from MAP in 64% of the 702 pints of retail milk sampled from California, Minnesota and Wisconsin. That DNA was not viable, but indicated that the milk had been exposed to MAP. The results revealed that viable MAP, which causes Johne�s was present in almost three out of every 100 bottles of milk.
However, Ellingson pointed out, pasteurization is not intended to kill every microorganism. �Pasteurization is not a lethality step, meaning it sterilizes milk.� Rather, he explained, pasteurization aims at reducing microorganisms through a �log reduction kill� that prevents them from reaching risky levels.
MAP is enormously tough. �It knows how to survive in multiple ranges of temperature and multiple ranges of acidity,� he said. �The organism is a survivor.�
That retail milk study �was developed to help farmers,� Ellingson reported, �to try to get the organism reduced on the farm and improve farmer�s economics. We know Johne�s is a big economic issue.�
Other researchers had tested milk pasteurized in laboratories to simulate commercial conditions. However, Ellingson said, �The real scientific laboratory is on the shelf of all of the grocery stores.� In the testing, �Every month, we took the same amount of samples from the same locations in the same states.� The samples were �double-blinded� and tested under the Marshfield protocol and by an independent lab.
(Feedstuffs, September 19, 2005; pg 33)
For more information contact Clell Bagley at email@example.com or (435) 797-1882.