Direct sunlight, heat and some disinfectants kill the organism. Even with a normal appetite and good feed, affected animals lose weight. Milk production is lessened and diarrhea develops. The diarrhea occurs off and on, eventually becoming chronic and does not respond to treatment. A low grade fever may develop and some animals will have a swelling under the jaw.
Animals can die within weeks to months after symptoms appear.
In most cases of Johne s Disease, symptoms do not appear until the first or second lactation, even if the animal contracted the bacteria as a young calf. Age of the animal, amount of bacteria present, genetics and stresses such as calving or moving to a new environment may be determining factors as to when clinical disease or symptoms are noticed. Cattle may also have subclinical infections during which no symptoms of diarrhea or weight loss are seen. However, they do not produce as much milk and may be more susceptible to other problems, such as infertility. Johne s Disease is spread by feed and water that is contaminated with the bacteria.