Reduced Severity of Disease Associated With Feeding a Pharmacologic Amount of Zinc in a Laboratory Mouse Model of Swine Dysentery

University of Nebraska 1995 Swine Day Report. Swine dysentery is a highly contagious diarrheal disease of growing and finishing pigs which continues to cost an estimated $115.2 million to the United States pork producers each year. The disease is caused by the spiralshaped bacterium, Serpulina (Treponema) hyodysenteriae and is characterized by severe bloody diarrhea, reduced weight gain and death of susceptible pigs. When introduced in an uninfected herd, the disease quickly becomes established, requiring continuous medication at a cost of more than $8.00 per pig going to market. Although the cause of the disease has been known since the early 1970s, disease control strategies have essentially remained the same; medication of animals with expensive residuecausing antimicrobials and sanitation of premises. Serpulina hyodysenteriae produces a toxin capable of destroying red blood cells and killing white blood cells that are involved in the pigs immune defense. Production of intestinal damage in animals inoculated with partially-purified toxin suggests that the toxin is involved in the disease. We have shown previously that the production of the toxin by S. hyodysenteriae can be greatly reduced or completely eliminated by adding various amounts of zinc sulfate (ZnSO4) to culture medium used in the laboratory. Based on that result, we hypothesized that dietary zinc compounds could affect the severity of intestinal infection by S. hyodysenteriae. Indeed, a group of researchers had noted reduced severity of dysentery in swine fed zinc-supplemented diets, but the benefit of this approach was not evaluated under wellcontrolled laboratory conditions. The purpose of the present investigation was to assess the prophylactic effect of a pharmacologic amount of different, feed-grade zinc compounds on infection and production of intestinal damage in laboratory mice inoculated with S. hyodysenteriae. Laboratory mice were chosen because they have been extensively used as a model to evaluate intestinal damage caused by S. hyodysenteriae infection.