Most common age Johne's disease (Mycobacterium paratuberculosis) is diagnosed?

Most common age Johne's disease (Mycobacterium paratuberculosis) is diagnosed?

• A. < 2 years
• B. 2-3 years
• C. 4-6 years
• D. > 8 years

Answer: (C)

Johne's disease is a chronic, slowly progressive infection caused by Mycobacterium paratuberculosis. Infection typically occurs in calves, but the disease takes many years to develop to the point of clinical illness, so signs and diagnosis usually appear in middle age. In cattle and many small ruminants, the most common age range for clinical disease—and thus for diagnosis—is four to six years. Younger animals are often subclinical, and while older animals can be affected, the peak likelihood of diagnosis sits around mid-life.

Johne's disease is a chronic, slowly progressive infection caused by Mycobacterium paratuberculosis. Infection typically occurs in calves, but the disease takes many years to develop to the point of clinical illness, so signs and diagnosis usually appear in middle age. In cattle and many small ruminants, the most common age range for clinical disease—and thus for diagnosis—is four to six years. Younger animals are often subclinical, and while older animals can be affected, the peak likelihood of diagnosis sits around mid-life.