Pigs of all ages are susceptible to intestinal diseases, and diarrhea is the clinical sign common to nearly all such disorders. Infectious agents that cause enteropathies are typically transmitted via the fecal-oral route. More than 20 etiologic agents, including bacteria, viruses, and parasites, can cause primary intestinal disease in pigs. Some other viruses, including sapovirus, adenocirus, and enterovirus, also have been isolated from the intestines of pigs but are not associated with economically consequential disease.
Porcine circovirus type 2 Porcine Circovirus Diseases (PCV 2) (PCV2) may be isolated from the intestines of pigs with diarrhea; however, it is more commonly associated with several multisystemic diseases, including postweaning multisystemic wasting syndrome. Diarrhea in a herd may be due to a single agent; however, polymicrobial infections are common. Because several porcine enteric diseases are more common during different production stages, differential diagnosis is best considered by age group ( see Table: Diarrheal Diseases in Pigs by Age Group Diarrheal Diseases in Pigs by Age Group 
). A specific case definition, based on clinical signs and gross lesions at postmortem examination, will help guide appropriate tissue sample collection and laboratory testing.
