johnes
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Texas PaPaw
Well-known member
Way I understand it screws up the intestinal lining where they can't absorb the feed nutrients. Essentially over time they will stave to death even though eating well.
Rafter S
Well-known member
Correlations have been made between Johnes disease in cattle and Chrones disease in people, but it is not settled science, a lot of works need to be done to prove if there is or isn't a meaningful connection. Pasteurization is an effective method of killing Johnes, so the disease is not a concern in commercial milk production. Raw milk could potentially have some risk, but there are a host of other pathogens I would be more worried about.
The greatest risk for nursing calves to pick up Johnes is through consumption of colostrum for an infected cow. It would be prudent not to keep those animals for replacements.
The greatest risk for nursing calves to pick up Johnes is through consumption of colostrum for an infected cow. It would be prudent not to keep those animals for replacements.
Lucky_P
Well-known member
Tons of current info here: johnes.org
Calves born to infected cows are infected in utero or via ingestion of organisms passed in colostrum/milk - and from fecal material containing the bacteria - 'clinical' cows may be seeding 60 million organisms per day into the environment. In a beef herd, calves born to an infected dam are 10X more likely to be infected than herdmates born to noninfected cows...but all are at risk, due to fecal contamination. We generally recommend NOT keeping offspring born to known infected dams.
Resistance to infection increases as animals get older, but with massive or constant exposure, even older animals may become infected.
Routine pasteurization is not effective in killing the Johne's organism in milk. It can - and has been - cultured from milk off the grocery store shelves. Lab experiments where they 'spiked' milk samples and then pasteurized them showed no significant decrease in bacterial colony counts of M.avium subsp. paratuberculosis (MAP).
Pasteurization temps/times are established to kill important human pathogens; Coxiella burnetti, specifically. Due to its thick waxy cell wall, MAP survives routine pasteurization.
At this point, the connection between MAP and Crohn's Disease in humans is unproven...but there are some aspects of the correlation that seem plausible.
Calves born to infected cows are infected in utero or via ingestion of organisms passed in colostrum/milk - and from fecal material containing the bacteria - 'clinical' cows may be seeding 60 million organisms per day into the environment. In a beef herd, calves born to an infected dam are 10X more likely to be infected than herdmates born to noninfected cows...but all are at risk, due to fecal contamination. We generally recommend NOT keeping offspring born to known infected dams.
Resistance to infection increases as animals get older, but with massive or constant exposure, even older animals may become infected.
Routine pasteurization is not effective in killing the Johne's organism in milk. It can - and has been - cultured from milk off the grocery store shelves. Lab experiments where they 'spiked' milk samples and then pasteurized them showed no significant decrease in bacterial colony counts of M.avium subsp. paratuberculosis (MAP).
Pasteurization temps/times are established to kill important human pathogens; Coxiella burnetti, specifically. Due to its thick waxy cell wall, MAP survives routine pasteurization.
At this point, the connection between MAP and Crohn's Disease in humans is unproven...but there are some aspects of the correlation that seem plausible.
Lucky_P
Well-known member
In English...
Cattle(particularly calves) ingest the MAP bacteria. MAP are absorbed, intact, through specialized intestinal epithelial cells(Momotani cells, situated over the top of islands of lymphoid tissue in the small intestine), and are phagocytosed(ingested) by macrophages(mononuclear white blood cells) in the submucosa of the intestine.
Macrophages can kill most bacteria - but MAP lives happily inside the macrophages, and continues to grow and reproduce. Eventually, that macrophage ruptures, releasing all the MAP that grew inside it. More macrophages are recruited to ingest the MAP organisms. Rinse, repeat. Eventually, the accumulation of all those white blood cells recruited in an effort to corral/clean up the infection - which they're unable to do, effectively - causes thickening of the gut wall, and interferes with normal nutrient absorption. Diarrhea and tissue wasting(loss of body condition) results as a consequence of diminished nutrient absorption.
Diagnosis is problematic...
Because these Johne's-infected animals are exposed in utero or at an extremely young age, and because the macrophages cannot effectively kill the bacteria and present bacterial antigens to other immune cells... we see a condition of 'oral tolerance' - the animal's immune system does not 'recognize' the MAP bacteria as a 'foreign' agent until it reaches a critical 'tipping point' and the animal does not produce antibodies against MAP until just about the time they break with clinical disease... profuse diarrhea,wasting, and heavy fecal shedding of the infectious organisms.
So... these animals, which may have been infected very early in their life may not give a positive blood test or fecal culture until they are 3, 4, 5 (or more) years old...
Cattle(particularly calves) ingest the MAP bacteria. MAP are absorbed, intact, through specialized intestinal epithelial cells(Momotani cells, situated over the top of islands of lymphoid tissue in the small intestine), and are phagocytosed(ingested) by macrophages(mononuclear white blood cells) in the submucosa of the intestine.
Macrophages can kill most bacteria - but MAP lives happily inside the macrophages, and continues to grow and reproduce. Eventually, that macrophage ruptures, releasing all the MAP that grew inside it. More macrophages are recruited to ingest the MAP organisms. Rinse, repeat. Eventually, the accumulation of all those white blood cells recruited in an effort to corral/clean up the infection - which they're unable to do, effectively - causes thickening of the gut wall, and interferes with normal nutrient absorption. Diarrhea and tissue wasting(loss of body condition) results as a consequence of diminished nutrient absorption.
Diagnosis is problematic...
Because these Johne's-infected animals are exposed in utero or at an extremely young age, and because the macrophages cannot effectively kill the bacteria and present bacterial antigens to other immune cells... we see a condition of 'oral tolerance' - the animal's immune system does not 'recognize' the MAP bacteria as a 'foreign' agent until it reaches a critical 'tipping point' and the animal does not produce antibodies against MAP until just about the time they break with clinical disease... profuse diarrhea,wasting, and heavy fecal shedding of the infectious organisms.
So... these animals, which may have been infected very early in their life may not give a positive blood test or fecal culture until they are 3, 4, 5 (or more) years old...
kenny thomas
Well-known member
How is a test done to see if a cow/calf carries the bacteria?
Rafter S
Well-known member
kenny thomas":1l44780p said:
Your vet can draw blood and send it off to be tested. You should get the result in a few days.
You can call me a sucker, but I still buy into the USDA's line that pasteurization kills Johnes. I will admit it likely does not do as well against MAP as it does C. burnetii or M. bovis, but there is likely a significant decline in the number of viable organisms. Some may sneak through in milk samples with a high burden, but I don't know that we can say pasteurization doesn't kill most MAP. I know they found it in milk in grocery stores in Wales, or Scotland, or one of those half countries over there. I think the dairy people in the US were claiming that the high heat short time pasteurization protocol they used there differed from the US or something like that so we shouldn't worry and should all drink a gallon of milk each day. There's probably a little sneaking through, but most of it is likely getting killed. I probably should visit the lit on the topic and make sure I'm not digging myself a hole misremembering things I haven't looked at in a while, but it can wait til tomorrow, or the next day. Additionally, isn't milk pasteurization one of the mainstays of the Johnes prevention program in dairy herds?
