Grass silage contaminated with Mycobacterium avium subspecies paratuberculosis (MAP): a possible source of paratuberculosis infection in ruminants?

Mycobacterium avium subsp. paratuberculosis (MAP) is the causative agent of paratuberculosis (Johneʹs disease) in ruminants. Paratuberculosis can cause severe economic losses and is acknowledged as one of the most important diseases of ruminants today. High amounts of MAP can be shed in the faeces of infected individuals and can survive for a long period in the environment. In the presented trial, baled grass silage was inoculated with a MAP-suspension, and the viability of MAP was studied over time. Samples from the bales were taken at increasing intervals and subsequently tested for the presence of MAP by solid culture on Herroldʹs Egg Yolk Media (HEYM), liquid culture and real time Polymerase Chain Reaction (PCR) for the IS900 and F57 fragments. No growth of MAP was observed at any time on solid or in liquid cultures, except at the time of inoculation; PCR detections were positive in the majority of the bales. From the results of the presented study, baled grass silage can be classed as a minor risk for the transmission of MAP.