Paratuberculosis

Paratuberculosis, also known as Johne's disease, is a chronic infectious disease affecting ruminants, including cattle, sheep, goats, and other wild ruminants. It is caused by the bacterium Mycobacterium avium subspecies paratuberculosis (MAP). The disease primarily affects the small intestine, leading to inflammation and thickening of the intestinal wall, which impairs nutrient absorption. This malabsorption results in progressive weight loss, diarrhea, and a decline in milk production, ultimately leading to debilitation and death.

Transmission of MAP typically occurs through the fecal-oral route. Infected animals shed the bacteria in their feces, contaminating the environment, feed, and water sources. Calves and lambs are most susceptible to infection, often acquired around the time of birth or during early life. The incubation period for paratuberculosis is long, usually several years, meaning that animals may appear healthy for an extended period while harboring the infection and shedding MAP.

Diagnosis of paratuberculosis can be challenging due to the long incubation period and the intermittent shedding of bacteria. Various diagnostic methods are available, including fecal culture, fecal PCR, blood tests (serology), and Johnin skin testing. These tests can help identify infected animals, although their sensitivity and specificity can vary.

There is currently no effective treatment for paratuberculosis. Antibiotics are generally not curative, and infected animals usually continue to shed MAP. Therefore, control and prevention strategies focus on herd management practices aimed at reducing exposure and transmission. These include biosecurity measures, testing and culling of infected animals, and management of young stock to minimize contact with fecal contamination. Paratuberculosis is a significant economic concern for livestock producers due to reduced productivity, animal losses, and increased management costs.