MELITON N. NOVILLA,^* VAGN FLYGER,^** ELLIOTT R. JACOBSON,^*** SUKANTA K. DUTTA,^*** EDOARDO M. SACCHl<sup>****


*</sup>Department of Pathology, Lilly Research Laboratories, P.O. Box 708, Greenfield, Indiana 46140, USA.
^**Department of Animal Sciences, University of Maryland, College Park, Maryland 20742, USA.
^***Department of Veterinary Science, University of Maryland, College Park, Maryland 20742, USA.
^****Central Animal Health Laboratory, Maryland Department of Agriculture, College Park, Maryland 20740, USA.