Clinical features of canine granulocytic anaplasmosis in 18 naturally infected dogs.
BACKGROUND
Anaplasma phagocytophilum, the causative agent of canine granulocytic anaplasmosis (CGA), is a Gram-negative intracellular organism transmitted by ixodid ticks. Thus far, only a few clinical studies evaluating dogs with CGA have been published.


OBJECTIVE
Evaluation of dogs naturally infected with A. phagocytophilum in which known co-infections were excluded.


METHODS
Eighteen dogs with CGA.


METHODS
Prospective study. The diagnosis of CGA was based on a positive PCR test result; dogs with co-infections were excluded. History, clinical findings, CBC, clinical biochemistry, infectious disease screening, diagnostic imaging, and the course of disease were evaluated.


RESULTS
CGA was diagnosed based on a positive PCR test for A. phagocytophilum; 10 dogs also had morulae in neutrophils. Six of 18 dogs were seronegative to A. phagocytophilum, the others were seropositive. All dogs were acutely ill. The most common clinical findings were lethargy, inappetence, fever, and splenomegaly. Abnormal laboratory results included thrombocytopenia, anemia, lymphopenia, hypoalbuminemia, and abnormally high plasma alkaline phosphatase activity. In 6 of 10 dogs tested, the platelet-bound antibody test was positive; Coombs' test was negative in 9 dogs. All dogs were treated with doxycycline and recovered. PCR testing as well as blood smear analysis for morulae were negative in 14 tested dogs 2-8 weeks after beginning treatment.


CONCLUSIONS
Clinical findings in dogs with CGA were nonspecific. Positive platelet-bound antibody test results suggest immune-mediated platelet destruction as an important pathogenic mechanism. With correct diagnosis and treatment, prognosis is good.
Kohn
B
B
Clinic for Small Animals, Faculty of Veterinary Medicine, Free University of Berlin, Berlin, Germany. kohn@vetmed.fu-berlin.de
Galke
D
D
Beelitz
P
P
Pfister
K
K
D000712:Anaplasmosis / Q000188:drug therapy / Q000473:pathology*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D004283:Dog Diseases / Q000188:drug therapy / Q000473:pathology*; D004285:Dogs; D004318:Doxycycline / Q000627:therapeutic use
D000900:Anti-Bacterial Agents; D004318:Doxycycline