James M. Rasmussen1, DVM; J. Allen Miller2, PhD; Arno Wünschmann3, DVM, Dr med vet, DACVP; Patricia J. Holman4, PhD; Tiffany M. Wolf1, DVM
Babesia odocoilei is an intraerythrocytic parasite transmitted by Ixodid ticks that is endemic in wild whitetail deer populations in various geographic locations within the United States.1,4
In 2003, two acute fatal cases of Babesia odocoilei occurred in musk oxen at the Minnesota Zoological Garden (MZG). A 6-year-old bull recently acquired from a zoo in Colorado succumbed to the disease in late September after being housed at the MZG’s quarantine facility for 13 days. A 1.5-year-old resident male succumbed to the disease approximately 2 weeks later. Both animals presented with sudden lethargy and hematuria and died within 36 and 72 hours respectively. The diagnosis of babesiosis was based upon seeing characteristic intraerythrocytic inclusions on blood smears. The second animal received one treatment of the babesicide imidocarb (Imizol®, 12%, Schering-Plough Animal Health, Union, NJ, USA) at 3 mg/kg IM SID, but the first animal died prior to treatment. Postmortem examination of both animals revealed icterus, anemia, hemoglobinuric nephrosis, hematuria, splenic red pulp hyperplasia, abomasal mucosal edema and hemorrhage, and small intestinal intraluminal hemorrhage. Babesia odocoilei infection was confirmed by 18S ribosomal RNA gene sequence analysis.3
The herd has subsequently been fed Mazuri ADF-16 with ivermectin 10 g/ton (Land O’Lakes Purina Feed, St. Louis, MO, USA) to provide an estimated daily intake of 0.09 mg ivermectin/kg body weight. A previous study on an isolated population of white-tailed deer (Odocoileus virginianus) indicated feeding ivermectin treated corn may be beneficial in reducing disease transmission by Ixodes scapularis.2
1. Holman PJ, Madeley J, Craig TM, Allsopp BA, Allsopp MTEP, Petrini KR, et al. Antigenic, phenotypic and molecular characterization confirms Babesia odocoilei isolated from three cervids. J Wildl Dis. 2000;36(3):518–530.
2. Rand PW, Lacombe EH, Holman MS, Lubelczyk C, Smith Jr. RP. Attempt to control ticks (Acari: Ixodidae) on deer on an isolated island using ivermectin-treated corn. J Med Entomol. 2000;37(1):126–133.
3. Schoelkopf L, Hutchinson CE, Bendele KG, Goff WL, Willette M, Rasmussen JM, Holman PJ. New ruminant hosts and wider geographic range identified for Babesia odocoilei (Emerson and Wright 1970). J Wildl Dis. 2005;41(4):683–690.
4. Waldrup KA, Kocan AA, Barker RW, Wagner GG. Transmission of Babesia odocoilei in white-tailed deer (Odocoileus virginianus) by Ixodes scapularis (Acari: Ixodidae). J Wildl Dis. 1990;26(3):390–391.