Anaplasma phagocytophilum is an obligate intracellular bacterium that causes febrile illness in humans and livestock. A 49-year-old woman was suffering from feverish symptoms, fatigue, arthralgia, general body pain, and anorexia for 2 weeks. Later, she visited the Bayannur Centers for Disease Control and Prevention Hospital in Inner Mongolia, China. Molecular-based diagnostic analysis of the patient's blood revealed that A. phagocytophilum p44 DNA was positive, but Brucella omp31, spotted fever group Rickettsia gltA, Orientia tsutsugamushi 16S rDNA, and Ehrlichia p28 were negative. The amino acid sequences of 9 A. phagocytophilum p44 clones obtained from the patient shared 44-100% similarity among them and were closely related to those of previously identified p44 clones from Canis familiaris (accession no. KJV64194) and from Ixodes persulcatus tick (no. BAN28309). Serological tests using the patient's serum showed that immunoglobulin M (IgM) and IgG titers to A. phagocytophilum antigens were 160 and 20, respectively, determined using indirect immunofluorescence assay, and the reaction to recombinant P44 proteins (rP44-1, rP44-18ES, and/or rP44-47) was confirmed using Western blot analysis. Thus, the results obtained in this study strongly suggest that the patient was infected with A. phagocytophilum. To our knowledge, this is the first case of human anaplasmosis infection in the Inner Mongolia Autonomous Region.
Keywords: Anaplasma phagocytophilum; China; Inner Mongolia; human granulocytic anaplasmosis (HGA); p44 multigene.