Abstract
Anaplasma phagocytophilum is one of the etiological agents of tick-borne rickettsial diseases. It is known as
human and animal granulocytic anaplasmosis. A three-year-old neutered Shih Tzu with no history of overseas
travel became anorexic and feverish one week after being bitten by a tick. The most relevant clinicopathological
findings were thrombocytopenia, neutropenia, and high levels of liver enzyme activity and CRP. The antibody
for A. phagocytophilum was weakly positive in the serum, and PCR analysis confirmed the diagnosis
of A. phagocytophilum infection. Treatment with doxycycline was successful in resolving the clinical signs of
thrombocytopenia and neutropenia. This represents the first documented case of canine A. phagocytophilum
infection to be reported in Japan.
