3. Environmental Determinants of SD Transmission
Although SD is a multifactorial disease which pathogenesis is complex and poorly understood, several factors have been associated with the occurrence of the condition. Thus, the outcome of infection by B. hyodysenteriae might be influenced by age [38], stress [39], acid secretion in the stomach [40], differences in the dose of the infectious agent, diet and the virulence of B. hyodysenteriae strains [41,42]. The following sections of the review emphasize the main environmental factors determining disease establishment and transmission, i.e., environmental survival of the pathogen, husbandry factors, role of vectors, relevance of pig’s diet, and interaction of the microorganism with gut microbiota (Figure 1).