Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 7/31/2014
Publication Date: 10/31/2015
Citation: Stabel, J.R., Bannantine, J.P., Hostetter, J. 2015. Mycobacterium avium subsp. paratuberculosis infection, immunology and pathology of livestock. In: Mukundan, M., Chambers, M. Waters, R., Larsen, M., editors. Tuberculosis, Leprosy, and Mycobacterial Diseases of Man and Animals: The Many Hosts of Mycobacteria. Boston, MA: Centre for Agriculture and Biosciences International. p. 512-537.
Interpretive Summary: Johne's disease is a chronic, debilitating intestinal disorder in cattle characterized by diarrhea, reduced feed intake, weight loss and death. Cattle usually become infected as young calves by ingesting feces containing the causative bacteria. However, symptoms of disease do not usually present themselves until the animals reach 3 to 5 years of age or even older. During this time the animal is infected and may be shedding the organism in its feces without showing any clinical signs of disease. In addition to reduced milk production by these animals, they also present a potential infective threat to the rest of the herd. Johne’s disease is difficult to manage and control on-farm. This chapter reviews information on the infection process, immune responses to infection, and pathogenesis. Understanding the host immune response to this pathogen as well as the pathogen itself will help us develop new diagnostic tools and vaccines to prevent the spread of disease.
Technical Abstract: Mycobacterium avium subsp. paratuberculosis (MAP) infection in ruminants leads to a chronic and progressive enteric disease (Johne’s disease) that results in loss of intestinal function, poor body condition, and eventual death. Transmission is primarily through a fecal-oral route in neonates but contaminated colostrum, milk, and in utero routes have also been described. An interesting and challenging feature of MAP infection is that it traverses both subclinical and clinical stages. The subclinical period is prolonged, often lasting years, and animals are often asymptomatic, making detection of infected animals difficult. Initially after infection and throughout the subclinical period the bacterial load is low and enteric lesions are absent or difficult to identify. Stressors such as parturition and concurrent disease have been incriminated in progression to clinical disease. It has been suggested that an immunologic disruption occurs to push the animal towards a more clinical presentation of disease but the exact mechanism(s) for this are unclear. During the clinical period animals will lose weight and milk production will decrease. Diarrhea is common and is often intermittent. Large numbers of bacteria are shed in the feces during this phase of infection, which can heavily contaminate the environment. This book chapter describes the process of infection, host immune responses to infection and subsequent pathogenesis, as well as current diagnostic tools and vaccines that have evolved and improved due to recent advances due to our understanding of the pathogen. Current information on the genomics and proteomics of the pathogen and comparative analyses with other mycobacterial pathogens is presented.