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Anaplasma phagocytophilum infection in dogs: 34 cases (2000–2007)

Jennifer L. Granick DVM, MS, DACVIM1, P. Jane Armstrong DVM, MS, MBA, DACVIM2, and Jeff B. Bender DVM, MS, DACVPM3
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  • 1 Department of Veterinary Clinical Sciences, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108.
  • | 2 Department of Veterinary Clinical Sciences, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108.
  • | 3 Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN 55108.

Abstract

Objective—To determine demographic characteristics of dogs from the upper Midwest infected with Anaplasma phagocytophilum and identify clinical and clinicopathologic abnormalities and response to treatment.

Design—Retrospective case series and owner telephone survey.

Animals—34 dogs with granulocytic anaplasmosis.

Procedures—Records were reviewed for information on signalment, history, physical examination findings, clinicopathologic and serologic findings, and treatment. Owners were contacted by telephone within 4 months after dogs were discharged.

Results—Median age was 8 years. Distribution of month of diagnosis was bimodal, with 15 dogs examined during May or June and 11 others examined during October or November. Camping and hiking were the most frequently reported tick exposure activities. Lethargy (25/34) and anorexia (21/34) were the most common initial complaints, fever was the most common clinical sign (27/32), and thrombocytopenia was the most common clinicopathologic abnormality (21/22). Fifteen of 20 dogs were seropositive for antibodies against A phagocytophilum. Doxycycline was prescribed for 31 dogs, and clinical signs and fever resolved within 3 to 5 days. Median time for platelet count to return to reference limits was 7 days. No owners reported clinical sequelae when contacted after dogs were discharged.

Conclusions and Clinical Relevance—Results suggested that granulocytic anaplasmosis should be suspected in dogs in endemic areas examined because of fever, lethargy, or thrombocytopenia, especially in dogs examined during the late spring or early fall. Treatment with doxycycline was successful in resolving clinical signs and thrombocytopenia.

Contributor Notes

Dr. Granick's present address is the Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California, Davis, CA 95616.

Address correspondence to Dr. Bender.