Bovine Immunity and Vitamin D 3 : An Emerging Association in Johne's Disease.

Mycobacterium avium subspecies paratuberculosis (MAP) is an environmentally hardy pathogen of ruminants that plagues the dairy industry. Hallmark clinical symptoms include granulomatous enteritis, watery diarrhea, and significant loss of body condition. Transition from subclinical to clinical infection is a dynamic process led by MAP which resides in host macrophages. Clinical stage disease is accompanied by dysfunctional immune responses and a reduction in circulating vitamin D 3 . The immunomodulatory role of vitamin D 3 in infectious disease has been well established in humans, particularly in Mycobacterium tuberculosis infection. However, significant species differences exist between the immune system of humans and bovines, including effects induced by vitamin D 3 . This fact highlights the need for continued study of the relationship between vitamin D 3 and bovine immunity, especially during different stages of paratuberculosis.