Consistent Johne’s Disease Testing Checks Beef, Dairy Disease Level
Regular diagnostic testing for Johne’s disease in beef and dairy herds is important because it keeps producers informed about the disease level in the herd, said Jennifer Street, Idaho State Animal Health Laboratory Principal Biologist.
“It’s very important that the producers in the beef and the dairy industry be regularly checking their herds for Johne’s disease,” said Street. “It is not uncommon for cattle to go asymptomatic in their herds. Therefore, they’re spreading the disease throughout their entire herd. If [producers] screen their animals on a regular basis, it’s all about catching the problem early, before needing to eradicate the problem once it has set it. At that point, it’s probably not good for that business owner’s livelihood – it just wipes out their herd.”
The Idaho State Animal Health Laboratory offers several different screening methods that test for Johne’s disease. Historically, they used culture which took weeks or months to get results. Now, they offer ELISA which checks to see if antibodies are present in the animal and when positive, it indicates the animal has been exposed to the disease agent at some point in time.
“More so now, we are actually using PCR, which is a DNA-based test to screen and, not only that, but to confirm if the animal does have Johne’s or not,” she said. “The Johne’s process for testing is so much quicker, and the sensitivity and the specificity for this new test is just amazing compared to the old methods.”
Because Johne’s disease is no longer regulated in Idaho, Street says they are seeing an increase in cases.
“Calves can be born with it, and they’ll be asymptomatic, so they may not show symptoms until they’re adults,” she said. “At that point, you probably have a problem, in which case it’s always best to check with either your local veterinarian or your state veterinarian and find a way to manage the herd and to test and screen for Johne’s.”
With PCR, the lab is able to “pool” samples, meaning they can take five fecal samples from a cow, and combine them into one test. Combining samples saves the producer money and if there is a positive result, the diagnostician can go back to the original samples and retest the samples individually to identify the positive animal or animals.
“The sensitivity of the test is very high, so we will pick it up if it’s there,” she said.