[1] Univ Turin, Dipartimento Prod Anim Epidemiol Ecol, I-10095 Grugliasco, TO, Italy
[2] Univ Illinois, Dept Pathobiol, Urbana, IL 61802 USA
[3] Michigan State Univ, Dept Microbiol & Mol Genet, E Lansing, MI 48824 USA
[4] Univ Illinois, Dept Nat Resources & Environm Sci, Urbana, IL 61801 USA
[5] Michigan State Univ, Dept Fisheries & Wildlife, E Lansing, MI 48824 USA