04/03/2026
Our herd once again tested negative for CAE and Johnes- but with a hiccup........
It is inevitable in the over 30 years we have been testing that a positive (False) would occur.
Tests are not 100% accurate 100% of the time. It depends on what type of test and the sensitivity and specificity level of the test.
So here is our saga of the false positive Johnes and why one of the Top bucks in Canada ended up being put down.
We bought a buck who was ranked #2 in Canada for type behind his son! And ranked #5 in Canada combined MILK and TYPE in Canada. He has several lovely daughters in milk. We have one who was unbeatable as dry yearling in the ring last year.
He had come from a farm that test regularly, in fact he had just tested Negative VIA f***l PCR just before we bought him. He had consistent negative Johnes f***l PCR tests from the breeder and previous owner.
The issues, he arrived thin, which is not unusual for mature buck in full rut, and he had very loose manure. His manure would go from almost normal to basically shooting diarrhea in the same day! This was highly unusual. On inquiry with the previous owner, it was indicated he had a delicate stomach and would have loose manure periodically with any change.
We had the vet out to assess him as I had run out of management protocols (worming, diet, etc.) to get him on track manure wise.
I had sent in ANOTHER F***l PCR it came back negative.
The vet specialises in ruminants which is rarity here on the island. We discussed options (looked at all the negative Johnes tests) and she stated he looked like he had an autoimmune disease.
I had her draw blood on the rest of the herd to send of for our herd routine testing. I asked should I have him done again as he just had serology (CAE) 2 months prior by the previous owner and TWO negative Johne f***l PCR tests in as many months.
She said it would be a good idea to test him via serology given his signs.
So, we did. His serology on Johnes came back positive and CAE was negative.
It is not uncommon now for the Abbotsford Ag lab to have false positive serology Johne’s test. As they changed test somewhere around 2022-23. Several other breeders have also had issues with false positives.
IF he had been a younger animal and IF he had not been presenting signs which can indicate Johnes (Thin condition and loose manure) I would not have worried and would have had the vet out to resend blood tests to WADDL.
But he was older and had signs which could indicate Johnes. So, we worked with the Vet. With the new serology test being positive, she was convinced he had Johnes.
Here’s why the vet came to that conclusion:
A negative f***l PCR is not all that informative.
Why?
Johnes is an INTERMITENT shedding disease. Meaning bacterium is not shedding continuously in the manure. F***l PCR is ONLY the gold standard IF the test is POSITIVE. There is almost no room for false positive in f***l PCR.
Why do I use Serology over PCR? With Johnes the animal will most likely seroconvert before they start to shed in the manure. This means serology will most likely pick up a positive animal before f***l PCR testing will. Thankfully in 30 years plus of testing this is the first time we have seen Positive result in our herd, and of course it turned out to be false.
A negative Serology test is good indicator that that animal is indeed negative at that point. Whereas positive serology test always needs to be confirmed with either necropsy or f***l PCR.
But if they have just seroconverted they most likely won’t test positive on a f***l PCR test, so that ONLY leaves a necropsy/ histology to determine if the animal is positive or if it was false positive serology test.
So, we now had a buck that had tested positive via serology, had classic signs of Johnes and was an older animal, which is when Johnes typically rears its ugly head. Plus, we had a ruminant vet who had examined him several times and she firmly believed he had Johnes due to the signs he was exhibiting.
That only left the option of putting him down for necropsy to confirm. BUT even then, the pathologists who I spoke with and emailed extensively, stated that there could be a slight possibility that they miss picking up Johnes bacterium from the intestinal lymph nodes if he has just seroconverted. Unlikely but a possibility… Really…yes really …I was being to really despise this insidious disease!
Statement from the pathologist:
“Here are my thoughts on the serology test:
• There may be a very low level of infection with Johne’s (enough to trigger an immune response but not enough to detect on PCR or histopathology)
• The results may be false positives. This is most likely to occur in goats exposed to caseous lymphadenitis, as that bacterium produces antibodies that cross react with those produced by Johne’s. Do you know if your herd or the source herd were ever exposed to caseous lymphadenitis?”
No, he was never exposed to CL (spoiler alert, nothing showed up in necropsy either…WHEW!!)
As side note I wonder if CL vaccines could cause an issue here.
Anyway, had the vet out again had him put down and helped with the necropsy. The vet sent everything off in duplicate. Each portion was divided in two, one portion in formalin and one frozen to ensure that nothing was missed or even if one was not viable in package the other portion would be.
And yes, by this point the costs were racking up BIG time, but I had to know.
Thankfully we had him in a quarantine area the entire time we had him which was about two months. So, if the necropsy results came back positive, we only had small area to thoroughly disinfect. Which was a very and I mean VERY small thing to be thankful for.
Anyway! We had also sent off blood work again to the Abbotsford Ag lab, and f***l.
AS WELL we send blood and f***l to WADDL.
WADDL recently posted that they have gone back to the prior ELSIA test as the current test had too many false positives.
Abbotsford Ag lab f***l PCR negative again and Blood serology positive again.
WADDL blood serology test came back NEGATIVE along with f***l PCR NEGATIVE.
We had conflicting serology test results.
Now had to wait from the necropsy results………it seemed like forever>>>
They came back:
Diagnosis:
Lymphoplasmacytic and eosinophilic enteritis (LEE)
Comments: The history and microscopic lesions in this goat are consistent with LEE, a condition of small ruminants that has only recently be described (see Pitel et al. J Vet Intern Med. 2021; 35:1620-1625). The diagnosis of this form of inflammatory bowel disease is based on compatible histopathological lesions in combination and exclusion of Johne's disease (note that PCR for Mycobacterium paratuberculosis was negative) and parasitism. The cause is not well understood but treatment with immunosuppressive therapy has been successful. I am performing special stains on the affected tissues for Johne's to make that it was not missed on PCR. Addendum 2026-02-18: No Mycobacterium spp. could be observed on specials stains.
What??? He had a rare newly discovered disease of goats, but NOT
Johnes…..
UGGGH….what that heck is LEE?
It turns out it is an autoimmune disease, so the vet had been right in initial visit!! Hats off to her!
LEE is not contagious…whew!!! It does not appear to be inheritable …whew…..
It seems as far as I can read from the research LEE is brought on by high parasite load at some point in time, which causes damage to the intestinal lining. But only time will tell if that is the cause of this autoimmune disease.
Thankfully our vet also conferred with the Ag Lab pathologist as well as the large animal internal medicine team at the Atlantic Veterinary College and this is the vet response:
“…. because none of the confirmatory f***l PCR tests OR histology have come back positive, then your herd can be considered negative.” YAY!
Take away points:
Serology will most likely pick up Johnes before f***l PCR.
A Positive serology test needs to be confirmed by PCR or histology to rule out a false positive.
Several herds in BC have had false positives at the Abbotsford Ag lab. WADDL down in the USA has gone back to the old test, which has less false positives.
Johnes is a slow progressing disease, a positive serology test on older animals if far more concerning than on a younger animal.
F***l PCR test that is negative is not that informative as Johnes bacterium is shed intermittently. It means they MAY not be shedding at that moment or in the part of the manure that was tested.
F***l PCR Positive means they have Johnes.
Looking forward:
It looks like three of our does were bred to him when he first arrived. So, with excitement and some sadness we look forward to seeing what his last kids will be.
This is a reminder, that testing for disease particularly one like Johnes is never cut and dry.
My hats off to everyone who has had a false positive and takes the time to post about it, as ultimately it benefits the goat community at large.
We are confident he did not have Johnes as confirmed by our Vet.
BUT the cost was so high…not the money, time and stress, but that Hat Trick had to pay the final cost, which hurts the most.
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