Hemoparasite Infections in Snowy Owls (Bubo scandiacus)
American Association of Zoo Veterinarians Conference 2017
Christy L. Rettenmund1, DVM, DACZM; Kendra C. Baker2, DVM; Samantha J. Sander1, DVM, DACZM; Anne E. Rivas3, DVM; Kaitlin C. Green1, BS, RVT; Lisa Mangus4, DVM, PhD, DACVP; Ellen Bronson1, Med Vet, DACZM
1The Maryland Zoo in Baltimore, Baltimore, MD, USA; 2Humane Rescue Alliance, Washington, DC, USA; 3Wildlife Conservation Society, The Bronx Zoo, Bronx, NY, USA; 4Department of Molecular and Comparative Pathobiology, School of Medicine, Johns Hopkins University, Baltimore, MD, USA


Hemoparasites including Plasmodium, Leukocytozoon, and Haemoproteus spp. are a common finding on blood smears of various avian species. Wild passerine birds often serve as reservoirs for these vector-borne hemoparasites, and most hemoparasites found in raptor species are associated with subclinical infection rather than overt disease.2,4-5 Very few documented reports of hemoparasite-associated disease in raptors exist.1,3,6 This case series describes five cases of hemoparasite infection in snowy owls (Bubo scandiacus). Of these cases, one mortality was attributed to hemoparasite infection, and Plasmodium spp. infection contributed to the death of a snowy owl in another case. The remaining three infected snowy owls were treated with primaquinea (1 mg/kg every 7 days for five doses, then SID for 10–15 doses PO) and chloroquineb (10 mg/kg loading dose, then 5 mg/kg SID for three doses, then every 7 days for four doses, then SID for 10–15 doses PO) and survived the infection. Based on serial blood smear monitoring, hemoparasite burdens decreased with treatment. Hemoparasitic infection does not appear to be benign in snowy owls, as it is considered to be in other raptor species. Increased environmental temperatures, stress, novel pathogen exposure, and concurrent disease processes may contribute to this morbidity and mortality in this species.

Environmental changes including the addition of fans to cool the exhibit and improved vector control have been implemented. Over the subsequent 2.5 years, lower parasite burdens have occurred on blood smears, and owls have remained asymptomatic without administration of anti-malarial medications.


a. Taylors Pharmacy, Winter Park, FL, USA
b. Rising Pharmaceuticals, Inc., Allendale, NJ, USA


The authors would like to thank the animal care staff at the Maryland Zoo in Baltimore for the diligent care they continue to provide for these birds. The authors also acknowledge the valuable collaboration with Project SNOWstorm, specifically Dr. Cindy Driscoll, David Brinker, and Dr. Erica Miller.

Literature Cited

1.  Evans M, Otter A. Fatal combined infection with Haemoproteus noctuae and Leukocytozoon ziemanni in juvenile snowy owls (Nyctea scandiaca). Vet Rec. 1998;143:72–76.

2.  Ferrell ST, Snowden K, Marlar AB, Garner M, Lung NP. Fatal hemoprotozoal infections in multiple avian species in a zoological park. J Zoo Wildl Med. 2007;38:309–316.

3.  Harasym C. West Nile virus and hemoparasites in captive snowy owls (Bubo scandiacus)—management strategies to optimize survival. Can Vet J. 2008;49:1136–1138.

4.  Levin I, Parker G. Haemosporidian parasites: impacts on avian hosts. In: Miller RE, Fowler ME, eds. Zoo and Wild Animal Medicine, Current Therapy. Volume 7. St. Louis, MO: Elsevier Saunders; 2012:356–362.

5.  Remple J. Intracellular hematozoa of raptors: a review and update. J Avian Med Surg. 2004;18:75–88.

6.  Tavernier P, Sagesse M, Van Wettere A, Redig P. Malaria in an eastern screech owl (Otus asio). Avian Dis. 2005;49:433–435.


Speaker Information
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Christy L. Rettenmund, DVM, DACZM
The Maryland Zoo in Baltimore
Baltimore, MD, USA

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