Listeria monocytogenes septicemia in a foal.

Listeria monocytogenes is rarely reported as a cause of septicemia in foals. In this case, the foal had diarrhea 2 weeks prior to the onset of signs of lethargy, high rectal temperature, and leukopenia with a left shift. Listeria monocytogenes was isolated from the blood culture. The most commonly isolated organism causing septicemia in foals is Escherichia coli. Without the blood cultures, a definitive diagnosis would not have been possible.