These animals pose a risk to others in the herd by contaminating the environment. They have acute or intermittent watery diarrhea, weight loss, and a drop in feed efficiency and milk production. Intermittent signs at this stage usually progress to more severe infection. These animals will likely test positive on blood and fecal culture tests. Stage 4 is the end of the disease process.
Most animals appear very thin, with fluid diarrhea.
Animals may progress from Stage 2 to Stage 4 in just a few weeks. The best detector of Johne s is a fecal culture test. This method is slow requiring 12 weeks to 16 weeks of culture time in the laboratory. Blood tests, while less accurate than culture, are faster and less expensive. Blood testing can be used most effectively to confirm clinical cases or to test a group of animals in a herd.