Johne's Disease and PCR Testing

[Lonesome Pine]

Hello All,
Looking for help in assessing the result of a PCR test done on our 9 year old Jersey/Aberdeen cross cow. We had the vet out for another reason but while here she witnessed diarrhea from this cow. I had wormed everyone about a month ago and was concerned that perhaps the Bovimectin pour on hadn't worked for her. No sign of worms in test result but I authorized the vet to do the Johne's test, never thinking it would come back positive. So, the test was performed 36 rounds, with the limit being 42, before the shedding of the anti-bodies was found. She is healthy, eating well, no body condition change and about to calve.
Any thoughts would be most appreciated.
Many thanks,
Mary

 

[Stickney94]

It's been a bit since I had Johne's testing done -- my recollection was that blood was drawn and the test results came back in a range. Are you saying that the animals score was 36 out of 42 -- so high likelihood of positive? What did your vet recommend?

With that said, Johne's is a devasting disease to have in your herd. If you have an animal that tests as a potential carrier I'd cull the animal immediately.

 

[A.J.]

Hi Mary. I'm sorry to hear she has Johnes. That puts you in a tough predicament since she is about to calve. If she were mine, I would still go ahead sell her as soon as possible to help minimize the risk of further spread to the rest of your herd. If you don't want to sell her before she calves, I would quarantine her away from the rest of your herd, and sometime soon test the rest of your herd to see if any of the others might have it as well. Testing can be difficult though, as others might be carriers, but not test positive for it yet. That's one of the tough things with Johnes is they typically keep a strong appetite and seem fine overall other than the diarrhea, until they get in advanced stages and start losing weight rapidly. Many times stressful events like calving can trigger it and they can go downhill fast. @Lucky_P on here is a great source of information for this from a veterinary perspective.

 

[Ebenezer]

It's been a bit since I had Johne's testing done -- my recollection was that blood was drawn and the test results came back in a range. Are you saying that the animals score was 36 out of 42 -- so high likelihood of positive? What did your vet recommend?

With that said, Johne's is a devasting disease to have in your herd. If you have an animal that tests as a potential carrier I'd cull the animal immediately.

PCR is more accurate than the blood test from what I have read.

 

[SBMF 2015]

I've delt with a few Johnes cows over the years for other producers. There's a smell you'll never forget.
If a cow comes up suspect or positive on the blood test then quarantine and PRC test them.
I have never knowingly put a Johnes positive cow in the food chain. We have always destroyed them.

 

[CVHFarmsLLC]

I suspected Johnes in our herd at one point and remember a bit about the diagnosis. If I remember correct, you would be pretty safe with a nine year old cow as I believe Johnes symptoms shows at a much younger age. I guess maybe there is a chance it was picked up later in life.

As others have said, PCR is most accurate. We had a positive around 38 of 42 (I could be off a bit). I talked with the head vet at the Texas A&M lab and he explained that it could easily be a false positive. We now suspect it was acidosis I caused by poor feeding decisions I made in our first year in the business. We culled the cow and have had zero signs of Johnes since. I guess my point is, there is a reasonable chance something else is going on and you don't have Johnes. Looking back now, I laugh about it because I was absolutely convinced we had it and I had ruined our family's cattle business.