Comparative pathogenesis of enteric viral infections of swine

At least 11 enteric viruses belonging to 6 distinct families (Adenoviridae, Astroviridae, Caliciviridae, Coronaviridae, Parvoviridae, and Reoviridae) cause diarrhea in swine mainly during the nursing and immediate post-weanin g period. Most infect the small intestinal enterocytes, inducing various de grees of villous atrophy and subsequently a malabsorptive, maldigestive dia rrhea. In addition rotaviruses possess an enterotoxin (NSP4) which induces a secretory diarrhea in mice. These viruses have distinct predilections for different vertical (villus/crypt) and horizontal (duodenum, jejunum, ileum , colon) replication sites in the intestine and the diarrhea intensity is o ften related to the extent of viral replication at these sites. In addition concurrent infections with multiple enteric viruses can produce synergisti c or additive effects leading to more extensive villous atrophy throughout the intestine and more severe and prolonged diarrhea. Knowledge of enteric viral replication sites and comparative mechanisms of diarrhea induction ma y lead to new or improved vaccine strategies or therapeutic approaches for the prevention or treatment of these viral diarrheas.