[1] No Illinois Univ, Dept Math, De Kalb, IL 60115 USA
[2] Gen BioTechnol LLC, Indianapolis, IN USA
[3] Indiana Univ Sch Med, Dept Microbiol & Immunol, Indianapolis, IN USA
[4] Univ Missouri Columbia, Div Anim Sci, Columbia, MO USA
[5] Univ Missouri Columbia, Coll Vet Med, Comparat Med Ctr, Columbia, MO USA