Towards an Evidence-Based Treatment Protocol for Cervid Babesiosis: Pharmacokinetics of Imidocarb in White-Tailed Deer (Odocoileus virginianus)
American Association of Zoo Veterinarians Conference 2019
Ellie L. Milnes1,2,3, VetMB, DVSc; Pauline Delnatte3, DVM, DVSc, DACZM, DECZM (Zoo Health Management); Murray Woodbury4, MSc, DVM; Ron Johnson1, DVM, PhD, DACVCP; Ronette Gehring5, BVSc, MMedVet (Pharm), DACVCP; Dale A. Smith1, DVM, DVSc; Nicole Nemeth1,6, BA, DVM, PhD, DACVP
1Ontario Veterinary College, University of Guelph, Guelph, ON, Canada; 2Toronto Zoo, Toronto, ON, Canada; 3Current address: Ol Jogi Wildlife Conservancy, Nanyuki, Kenya; 4Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada; 5Faculty of Veterinary Medicine, Utrecht University, Utrecht, Netherlands; 6Current address: Southeastern Cooperative Wildlife Disease Study, University of Georgia, Athens, GA, USA


Cervid babesiosis, caused by infection of erythrocytes with Babesia odocoilei, is an emerging tick-borne hemolytic disease of cervids in North America.1-3 Clinical signs in affected animals include lethargy, respiratory distress, hemoglobinuria, icterus, and sudden death.1-4 Supportive care for cervids in hemolytic crisis includes anti-inflammatory drugs, fluid therapy to minimize the secondary renal effects of hemolysis, and blood transfusion in very anemic animals.4 Imidocarb, an anti-protozoal, has been used successfully to treat clinical babesiosis and eliminate parasitemia.1 This study was designed to investigate the pharmacokinetics of a single dose of imidocarb (3.0 mg/kg IM; Imizol® 120 mg/ml, Merck Animal Health, Intervet Inc., Madison, NJ, USA) in white-tailed deer (Odocoileus virginianus, n=10). Blood samples were collected at 14 time points over a 48-h period after drug administration, and plasma imidocarb concentrations determined by HPLC with UV detection. The mean±SE maximal imidocarb concentration was 880.78±81.12 ng/ml at 38.63±5.30 min post-injection. The distribution phase had a half-life of 25.90±10.21 min, and plasma imidocarb concentration declined with a terminal elimination half- life of 464.06±104.08 min. The rapid distribution and slow elimination of imidocarb in white-tailed deer following IM injection at 3.0 mg/kg may result in plasma concentrations remaining at therapeutic concentrations for at least 8 h. However, pharmacokinetic parameters are not necessarily comparable across species, and caution must be used in generalizing the results of the present study to other cervids. Clinical trials in parasitemic cervids are required to evaluate the efficacy of this dose of imidocarb as a treatment for cervid babesiosis.


Funding for this project was provided by the Toronto Zoo and the American Association of Zoo Veterinarians Wild Animal Health Fund.

Literature Cited

1.  Bartlett SL, Abou-Madi N, Messick JB, Birkenheuer A, Kollias GV. Diagnosis and treatment of Babesia odocoilei in captive reindeer (Rangifer tarandus tarandus) and recognition of three novel host species. J Zoo Wildl Med. 2009;40:152–159.

2.  Mathieu A, Pastor AR, Berkvens CN, Gara-Boivin C, Hébert M, Léveillé AN, Barta JR, Smith DA. Babesia odocoilei as a cause of mortality in captive cervids in Canada. Can Vet J. 2018;59:52–58.

3.  Petrini KF, Holman PJ, Rhyan JC, Wagner GG. Fatal babesiosis in an American woodland caribou (Rangifer tarandus caribou). J Zoo Wildl Med. 1995;26:298–305.

4.  Pastor A, Milnes E. Babesiosis in cervidae. In: Miller RE, Lamberski N, Calle PP, eds. Fowler’s Zoo and Wild Animal Medicine: Current Therapy. Volume 9. St. Louis, MO: Elsevier; 2019: 647–655.


Speaker Information
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Ellie L. Milnes, VetMB, DVSc
Toronto Zoo
Toronto, ON, Canada

Ontario Veterinary College
University of Guelph
Guelph, ON, Canada

Ol Jogi Wildlife Conservancy
Nanyuki, Kenya

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