Johne disease, also known as paratuberculosis, is a chronic contagious bacterial infection that primarily affects ruminants, including cattle, goats, and sheep. It is named after its discoverer, Heinrich Albert Johne, a German veterinarian who first identified the disease in the early 1900s.
The disease is caused by the bacterium Mycobacterium avium subspecies paratuberculosis (MAP), which primarily infects the intestinal tract of animals. Johne disease is characterized by a slow progression and a long incubation period, with infected animals typically not exhibiting clinical signs until several years after infection.
Infected animals shed the bacteria through their feces, contaminating the environment and potentially infecting other herd members through ingestion. The bacteria invade the intestinal lining, leading to chronic inflammation, thickening of the intestinal wall, and malabsorption of nutrients. As a result, infected animals may experience chronic diarrhea, weight loss, decreased milk production, and diminished overall health.
Diagnosis of Johne disease typically involves a combination of medical history, clinical signs, and laboratory tests, such as serological assays or polymerase chain reaction (PCR) tests. Unfortunately, accurate diagnosis is challenging due to the disease's long incubation period and intermittent shedding of bacteria.
While there is no cure for Johne disease, management strategies primarily focus on prevention and control to limit spread within herds. This includes maintaining strict hygiene practices, avoiding contaminated pastures, separating infected animals, and culling or removing animals with confirmed diagnosis.
