Granulocytic anaplasmosis in 63 dogs: clinical signs, laboratory results, therapy and course of disease

OBJECTIVES : To describe the clinical signs, laboratory results, therapy and course of disease in dogs with canine granulocytic anaplasmosis in which co-infections had been excluded. METHODS : Medical records of dogs naturally infected with Anaplasma phagocytophilum were retrospectively evaluated with regard to clinical signs and laboratory abnormalities at the time of presentation, therapy and course of disease. RESULTS : Nine hundred and seventy-four dogs with clinical signs suspicious for canine granulocytic anaplasmosis were tested for A. phagocytophilum DNA by modified real-time PCR; 72 dogs had a positive result. Nine of the positive dogs were excluded from further evaluation due to other diseases or lack of data. The most common clinical signs in the 63 A. phagocytophilum-positive dogs included in the study were lethargy and reduced activity (83%), fever (67%) and inappetence (63%). Thrombocytopenia was the most common laboratory abnormality (86%), followed by increased liver enzyme activities and hyperbilirubinaemia (77%), anaemia (70%), hypoalbuminaemia (62%) and leucocytosis (27%). Of 36 thrombocytopenic dogs tested for platelet-bound antibodies, 44% were positive. Of the 63 infected dogs, 59 (97%) recovered, two dogs died (epileptic seizures and immune-mediated haemolytic anaemia) and two were lost to follow-up. CLINICAL SIGNIFICANCE : In areas where it is endemic, canine granulocytic anaplasmosis should be considered as a potential cause of acute nonspecific clinical signs or immune-mediated disease if tick exposure cannot be excluded.