Case Report Journal of Veterinary Emergency and Critical Care 25(6) 2015, pp 789–794 doi: 10.1111/vec.12367 Splenic vasculitis, thrombosis, and infarction in a febrile dog infected with Bartonella henselae Steven G. Friedenberg, DVM, MS, DACVECC; Nandhakumar Balakrishnan, PhD; Julien Guillaumin, DVM, DACVECC, DECVECC; Edward S. Cooper, VMD, MS, DACVECC; Kristin Lewis, DVM; Duncan S. Russell, BVMS, DACVP and Edward B. Breitschwerdt, DVM, DACVIM Abstract Objective – To describe the clinical course and successful management of a febrile dog with polyarthritis, splenic vasculitis, thrombosis, and infarction that was infected with Bartonella henselae. Case Summary – An 8-year-old female spayed Labrador Retriever was referred to The Ohio State University Veterinary Medical Center Emergency Service for evaluation of limping, fever, vomiting, and malaise of 4 days’ duration. Physical examination abnormalities included generalized weakness, diminished conscious proprio- ception, bilateral temporalis muscle atrophy, and diarrhea. Peripheral lymph nodes were normal, and there were no signs of abdominal organomegaly, joint effusion, or spinal pain. Abdominal ultrasound identified a nonocclusive splenic vein thrombus. Fine-needle aspirates of the spleen revealed pyogranulomatous inflam- mation, mild reactive lymphoid hyperplasia, and mild extramedullary hematopoiesis. Splenic histopathology found marked, multifocal to coalescing acute coagulation necrosis (splenic infarctions) and fibrinoid necrotizing vasculitis. Bartonella henselae DNA was amplified by polymerase chain reaction and sequenced from the splenic tissue. The dog responded favorably to antimicrobials and was healthy at the time of follow-up evaluation. New and Unique Information Provided – Bartonella henselae is an incompletely characterized emerging ca- nine pathogen. This case report establishes a potential role for this bacterium as a cause of vasculitis and thromboembolism, which have not been previously reported in association with B. henselae infection in dogs. (J Vet Emerg Crit Care 2015; 25(6): 789–794) doi: 10.1111/vec.12367 Keywords: B. henselae, polyarthritis, splenic vasculitis, thrombosis From the Department of Veterinary Clinical Sciences (Friedenberg, Guil- laumin, Cooper), and the Department of Veterinary Biosciences (Lewis, Russell), College of Veterinary Medicine, The Ohio State University, Colum- bus, OH 43210; and the Intracellular Pathogens Research Laboratory, Center for Comparative Medicine and Translational Research, College of Veterinary Medicine, North Carolina State University, Raleigh, NC 27607 (Balakrishnan, Breitschwerdt). Supported in part by the state of North Carolina and a monetary donation from Bayer Animal Health. Dr. Nandhakumar Balakrishnan is funded as the Bayer Fellow in Vector Borne Infectious Diseases Research at the College of Veterinary Medicine, NorthCarolina State University. In conjunction with Dr. Sushama Sontakke and North Carolina State Uni- versity, Dr. Breitschwerdt holds U.S. Patent No. 7,115,385; Media and Methods for cultivation of microorganisms, which was issued October 3, 2006. He is the chief scientific officer for Galaxy Diagnostics, a company that provides diagnostic testing for the detection of Bartonella species in- fection in animals and human patients. All other authors have no potential conflicts. The funding agencies were not involved in the decision to pursue or provide testing for evidence of Bartonella spp. infection in this dog. Address correspondence and reprint requests to Dr. Edward B. Breitschwerdt, College of Veterinary Medicine, North Carolina State University, 1060 William Moore Dr, Raleigh, NC 27607, USA. Email: ed_breitschwerdt@ncsu.edu Submitted August 12, 2013; Accepted July 22, 2015. Abbreviation PCR polymerase chain reaction Case Description An 8-year-old female spayed Labrador Retriever was referred to The Ohio State University Veterinary Medical Center Emergency Service for evaluation of limping, fever, vomiting, and malaise of 4 days’ duration. When evaluated by a veterinarian 2 days prior to presentation, there was neck pain and temporalis muscle wasting, and the dog had a rectal temperature of 40.9°C (105.7°F). Complete blood count (CBC) abnormalities at that time included leukocytosis (25.0 × 10 9 /L [25.0 × 10 3 /L], reference interval 5.0 - 16.8 × 10 9 /L [5.0 – 16.8 × 10 3 /L]), neutrophilia (20.3 × 10 9 /L [20.3 × 10 3 /L], reference interval 3.0 - 11.6 × 10 9 /L [3.0 – 11.6 × C  Veterinary Emergency and Critical Care Society 2015 789