Provincial agriculture ministries, farmers and veterinarians are stepping up efforts to control Johne’s disease, a common intestinal illness that affects cattle and other ruminants. On Jan. 1, Ontario’s dairy industry launched an unprecedented four-year mass program of subsidized testing and culling of animals that have high levels of the Johne’s bacteria.
Suppressing Johne’s (pronounced “yoh-knees”), which is acquired by calves at birth but doesn’t usually cause diarrhea and weight loss until an animal is three or more years old, would be good for milk production. But there’s another reason for action. The pathogen that causes Johne’s, Mycobacterium avium paratuberculosis (MAP), is known to pass into milk and survive pasteurization. It may play a role in a human sickness estimated to affect more than 80,000 Canadians: Crohn’s disease.
The possibility is very speculative, though one Australian pharma company, Giaconda, is testing a mix of MAP-targeted antibiotics as a Crohn’s treatment. “I’d say there’s a big question mark around that hypothesis,” says Gerald Hauer, Alberta’s chief provincial veterinarian. “It has never been proven, and the literature always seems to be split down the middle.”
Researchers noticed as early as 1913 that Crohn’s disease lesions actually look a lot like Johne’s. And an August 2007 literature review in Lancet Infectious Diseases found that Crohn’s patients in 28 studies were, overall, much more likely to have MAP in their guts. What nobody knows is whether Crohn’s made those patients more vulnerable to MAP infestation, or whether MAP caused the Crohn’s.
With the question open, Canadian dairymen, mindful of the BSE/mad-cow ordeal their beef-raising brethren are still emerging from, aren’t waiting around passively for a food panic and the erecting of trade barriers.