In the sick animal, the diagnosis is made by use of blood tests. These tests use blood serum and consist primarily of two tests. This test is not very useful for determining cattle that may be shedding the organism and not yet showing symptoms of the disease. Culture of feces is the best test to diagnose shedding and clinically infected cattle. The main restriction of this test is that it requires seven to eight weeks for the organism to grow.
Some strains even require up to fifteen weeks.
A recent development in testing for Johne s disease is the DNA probe. Two tests that have been used to diagnose clinically affected cattle are the acid-fast stain of a smear of tissue from the large intestine and the intradermal or intravenous Johnin tests. These tests are unreliable and are not used much anymore. Your practicing veterinarian can arrange for the Oklahoma Animal Diagnostic Laboratory to run blood samples for the diagnosis of this disease. Prevalence of Johne s Disease in Oklahoma Johne s disease is present in cattle throughout Oklahoma, and the incidence appears to be increasing.