[1] Univ Glasgow, Fac Vet Med, Glasgow G61 1QH, Lanark, Scotland
[2] Hoechst Roussel Vet, D-65204 Wiesbaden, Germany
[3] Univ Utrecht, Div Parasitol & Trop Vet Med, NL-3508 TD Utrecht, Netherlands
[4] Louisiana State Univ, Sch Vet Med, Baton Rouge, LA 70803 USA
[5] Univ Pretoria, Fac Vet Sci, Dept Vet Trop Dis, ZA-0110 Onderstepoort, South Africa
[6] Univ Kentucky, Dept Vet Sci, Agr Expt Stn, Lexington, KY 40546 USA
[7] E Tennessee Clin Res Inc, Knoxville, TN 37922 USA
[8] Univ Guelph, Ontario Vet Coll, Dept Pathobiol, Guelph, ON N1G 2W1, Canada