Scientists with USDA’s Agricultural Research Service (ARS) have developed a new experimental vaccine to protect cattle from the bacterium that causes Johne’s disease. Johne’s disease (pronounced “Yo-knees”), also known as paratuberculosis, is a contagious, chronic and often fatal infection. The disease primarily affects cattle and other ruminants. Johne’s disease causes a gradual thickening of the intestines reducing nutrient absorption and resulting in weight loss, diarrhea and eventually death. The disease is named after the German veterinarian, H.A. Johne, who first described the disease in 1895. The economic cost of Johne’s disease is substantial due to later rebreeding, reduced weaning weights, and losing or culling cows before they have recouped their production costs.
Johne’s disease is caused by the bacterium Mycobacterium avium, subspecies paratuberculosis (MAP). This bacterium is closely related to bacteria that cause tuberculosis in cattle and humans. Calves are typically infected early in life through exposure to colostrum, milk or manure from a Johne’s infected cow. However, signs of the disease do not become apparent until years later. In the meantime, subclinical cattle (an infected animal that does not exhibit clinical signs) are shedding bacterium cells and infecting herd mates. MAP typically harbors and multiplies in the small intestine. MAP can also be spread to areas outside the intestine, such as the uterus, lymph nodes, udder, reproductive organs of bulls, and maybe excreted directly in milk or semen.
Unlike traditional vaccines that use cells of live, but weakened, or dead Johne’s causing baceteria, ARS researchers have focused on four proteins from the bacterium. Initial studies have been successful, rendering treated animals immune over the course of a year. The vaccine has shown little to no cross-reactivity with serological tests and the cocktail did not trigger blemishes at the injection site. Researchers note that additional efficacy trials and welcome collaboration with an industry partner to explore the patented vaccine cocktail’s commercial potential further. For additional information visit www.ars.usda.gov.