Brachyspira, the organism responsible for swine dysentery infections, is controlled at low concentrations of tiamulin and carbadox, according to a study at Iowa State University. Control by lincomycin was observed at much higher levels.

Some of the non-Brachyspira hyodysenteriae did exhibit higher levels of resistance to antimicrobial intervention, including Brachyspira species that may be pathogenic.

The findings in this study are important for pork producers to be aware of so they can adopt appropriate measures to identify and test for antimicrobial susceptibility if standard antibiotic treatments are not producing expected results. Not all Brachyspira are equally susceptible to antimicrobials commonly used to treat swine dysentery.

While the differences in susceptibility between Brachyspira species were not dramatic in this study, they may represent reason enough to conduct antimicrobial susceptibility

In the early 1990s, when cases of swine dysentery were at their peak, economic studies determined that swine dysentery cost the pork industry $115.2 million annually. Profit margins for a 220-lb. live weight hog in a swine dysentery-free herd were $7.44 compared to $1.61 for a swine dysentery-infected herd. It is likely that the differences in 2012 dollars would make the cost of swine dysentery even greater.

Having the capability to test Brachyspira isolates for their susceptibility to available antimicrobials could reduce these potential losses and support prudent use concerns.

Researcher: Tim Frana, DVM, Iowa State University. For more information, contact Frana by phone (515) 294-1950, fax (515) 294-3564 or e-mail