In addition, since Johne's is a slow-growing organism, it may take up to 16 weeks of incubation in the lab before a final result can be given. It detects antibodies in blood to M paratuberculosis . Animals not infected with M. paratuberculosis will test negative on the follow-up fecal culture and would be properly considered Johne's negative. However, these animals will need to be followed carefully. Necropsy of a suspect animal, with submission of tissue, blood, and fecal samples to the diagnostic lab, is another way to diagnose Johne's in a herd.
Lesions are very characteristic and numerous bacteria are commonly seen in lesions.
Cultures can be done on tissues, which gives more reliable results than culture of feces only. Prevention of Johne's Disease Producers who do not have Johne's disease should take every precaution to avoid introducing it to their herd. The most common way to introduce Johne's into a herd is through purchase of a Johne's infected animal. Inquire if the herd has an active Johne's surveillance program, including a testing program. This gives some measure of certainty whether or not the seller is concerned about Johne's disease and is looking for evidence of Johne's in their herd.