Result of the laboratory-based diagnostic test of human granulocytic anaplasmosis, 2018

Lee Kyeong Ah, Kim Hwanhee, Hwang Seon Do, Chun Jeong-Hoon, Hwang Kyu Jam
Division of Bacterial Diseases, Center for Laboratory Control of Infectious Diseases, KCDC

Human granulocytic anaplasmosis (HGA) is a zoonotic, tick-borne, infectious disease, transmitted mainly by Haemaphysalis spp. or Ixodes spp. Ticks are infected by the obligate intracellular bacteria Anaplasma phagocytophilum. In South Korea, HGA was first reported in 2014 and since then, there have been several reports of anaplasmosis cases. This study shows the results of laboratory diagnosis of HGA in suspected patients carried out in 2018 using immunofluorescent antibody assay (IFA) and polymerase chain reaction (PCR). We performed serological tests for HGA using immunofluorescent antibody assay (IFA) using the sera of 886 patients and amplification of the 16S rRNA gene of A. phagocytophilum by nested PCR of 328 blood samples. In the serological test using IFA, 189 (21.3%) of the 886 cases were positive for IgG or IgM against A. phagocytophilum (male: 105/189, 55.6% vs. female: 84/189, 44.4%). In the PCR test, 26 (7.9%) of the 328 cases showed a positive result. In serology, there were 32 cases which showed a 4-fold increase between the initial phase and the convalescence phase. According to the laboratory diagnostic criteria, the positive rate of HGA was 6.6% (80/1,214 cases), indicating a increasing pattern, compared with 1.7% (5/302) in 2016 and 5.0% (30/598) in 2017. The results provide evidence of prevalence of HGA in South Korea.

Keywords: Anaplasmosis, Anaplasma phagocytophilum, Laboratory diagnosis