[1] Philadelphia Zoo, 3400 W Girard Ave, Philadelphia, PA 19104 USA
[2] ARS, USDA, Anim Parasit Dis Lab, Beltsville Agr Res Ctr, Bldg 1001, Beltsville, MD 20705 USA
[3] ARS, USDA, Electron & Confocal Microscopy Unit, Beltsville Agr Res Ctr, Bldg 12, Beltsville, MD 20705 USA
[4] Univ Penn, Sch Vet Med, New Bolton Ctr, Penn Anim Diagnost Lab Syst, 382 West St Rd, Kennett Sq, PA 19348 USA