northeastern Ohio | junk fun - 4/11/2025 09:56
Clinical cases, or subclinical carriers also? I'm behind the times.
Both.
In the early 1990's, our state offered free Johnes testing and then published a list of Johnes free herds. We had never seen a clinical case in our herd, but we found a few carriers/shedders. We adopted all the control measures immediately, but year after year we continued to find a few carriers/shedders.
The funding for free testing dried up in the mid 2000's but we continued to test at our own expense. Fecal testing is the most accurate although the blood test is cheaper. We alternated for a couple years, but then went solely to fecal tests.
Following all the protocols, we reduced the number of shedders in our herd but never eliminated it. There was just too much of an environmental load that could not be overcome. A few calves would get exposed and the long incubation meant they would eventually shed before we could detect and cull them.
Rumensin was approved in 2004 for dairy cows and I think we started using it around 2007. By 2010, we finally had zero positive tests. I think the last time we tested was 2018 and did not have any positives.
Rumensin significantly reduces shedding and when coupled with all the other control measures can effectively eliminate Johnes: https://pubmed.ncbi.nlm.nih.gov/16631972/
I had a neighbor that had a large number of Johnes cases and shedders. His vet got approval to use the Johnes vaccine and they vaccinated every calf for years. It worked, but was expensive. And the animal could not be blood tested after vaccination because the antibodies from the vaccine would produce a positive Johnes test even though they did not have a clinical case. The fecal test would work, but he dropped testing in order to pay for the vaccine. I would not recommend this route.
In summary, Rumensin is part of the equation to get rid of Johnes. Put it in the calf and heifer feed as well as the cow ration. It breaks the cycle, but you also need to follow the other protocols to reduce all chances of transmission. |
Johnes control
