Herd Testing

What do we test for?

 

I am a big believer in herd testing. I have tested yearly for CAE/CL/Johne's since 2021. I test CAE and CL on everyone older than 6 months of age by blood. I have historically tested Johne's by ELISA, but I had what I believe is my first "false positive" ELISA Johne's* this year.  As a result, after consultation with Dr. Michael Collins, DVM, PhD at the Johne's Information Center, annual screenings for Johne's will be tested only by fecal PCR. Per his recommendation, I will do pooled fecal PCRs on everyone 1 year of age and older going forward. I also like to test does that will be in milk for Q Fever, but I do not consistently test every doe, every year for this. I like to test for all 4 diseases on animals in winter. This is at least 3 months after show season, and milking season has slowed down or stopped. It also is the perfect time to test my does within a couple months of kidding to make sure everyone is clear before the avalanche of babies happens. Testing for CL is more accurate by testing abscesses. I have had 2 abscesses since I started raising goats. Every abscess has been sent for culture. Both were negative.

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*See 2025 testing to see more about my false positive

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So, what are these diseases?

​​Johne's Disease pronounced "yo-knees"

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https://johnes.org/goats/faqs/

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Here is a great video about Johne's Disease (MAP) by Dr. Michael Collins DVM at Johne's Information Center

https://johnes.org/presentations-and-mini-lectures 

(scroll down to Johne's disease in goats)​

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Click here to go to Cornell's website

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Click here to see link to VMRD test( ELISA test used by WADDL). You will need to scroll down to Product Documents to see the study on goats. The study is small in my opinion, and while the study shows 100% sensitivity, the specificity is 98.5%, leaving room for 1.5% false positives. Anecdotally, it seems WADDL is having a much higher false positivity rate than study shows. Hopefully WADDL is taking a close look at these results. URBL and Texas A&M use IDEXX ELISA. Dr. Melissa Holahan, who works with WADDL, believes the VMRD is more sensitive in picking up early shedders than the IDEXX test.

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A few quotes from Dr. Michael Collins, DVM, PhD, DACVM 

"Many people test for Johne's disease using a blood test, called ELISA. What they fail to understand is that the ELISA is only a rapid, low-cost screening test and cannot definitively diagnose Johne's Disease. Only by using fecal sample can a diagnosis of Johne's disease be confirmed. A single negative fecal PCR indicates that the goat is not shedding MAP in its feces at the time of sampling. It significantly raises the probability the goat is not MAP-infected. However, due to the chronic nature of this bacterial infection, repeat testing at one year intervals is advisable. After 3 negative fecal PCR tests done a year apart by qualified labs you can be 99+% sure the goat is not MAP-infected. I recommend breeders not use the ELISA but only use the fecal PCR."

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"It is quite possible that the blood test was a false-positive. This is especially true of the goats who are in contact with backyard poultry...I recommend that breeders not use the ELISA but only use the fecal PCR for their annual herd test. To control costs, I further recommend that goat breeders use laboratories that are USDA-approved to pool samples (5 goat fecals per pool)." Click here to go to USDA page for list of approved labs. Scroll down to one labeled "Johne's disease-pooling methods'.

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CAE

Click here to go to Merck's Vet Manual

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CL

Click here to go to Merck's Vet Manual

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Q Fever

Click here to go to Merck's vet manual

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Information on Disease testing for goat owners

Click here to hear the podcast The Big 3:Testing your goats for CAE, CL, and Johnes 

Ringside with Dr. Melissa Holahan DVM

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