Herd Stratification to Reduce the Spread of Johne's Disease

Abstract

Johne's disease (JD) is a chronic, progressive enteric disease of ruminants caused by infection with Mycobacterium avium subspecies Paratuberculosis (MAP). Johne's disease causes major economic losses to the cattle industry. There is an age susceptibility to JD with younger cattle being more susceptible. Calves are generally infected as neonates. After a prolonged incubation period of two to ten years, initial clinical signs may develop, including severe progressive diarrhea and gradual weight loss, despite the persistence of a normal appetite. Typically, the infection develops in the ileum and gradually spreads to regional lymph nodes and other viscera. Over time, cattle become lethargic, emaciated and, in the terminal stages of disease, exhibit cachexia and severe watery diarrhea. MAP survives in the soil and the cattle environment for extended periods of time. Environmental contamination contributes to the pathogen load and infection rate of neonatal calves. In an attempt to reduce the pathogen load that neonatal calves are exposed to, these two cow herds were stratified by age and stage of production.