Occurrence of antibodies to Anaplasma phagocytophilum in patients with suspected tick-borne encephalitis

Abstract

Introduction and objectives: Human granulocytic anaplasmosis (HGA) is an emerging tick-borne infectious disease caused by Anaplasma phagocytophilum. In Europe, the first serological evidence of HGA was described in 1995 in Switzerland, and the first clinical case was confirmed in 1997 in Slovenia. Since then, many European countries, including Slovakia, have reported the occurrence of HGA. The aim of this study was to examine the occurrence of IgG antibodies against A. phagocytophilum in blood sera of humans with suspected tick-borne encephalitis.

Material and methods: 181 people were examined for the presence of anti-A. phagocytophilum IgG antibodies; 113 were patients with suspected TBE (65 males, 48 females), and 68 from the control group (18 males, 50 females). Respondents were aged 2-80 years (mean age: 31.39; STD: 17.1). Anti-A. phagocytophilum IgG antibodies were detected by the IFA IgG test. Relative risk (RR) and their 95% confidence intervals (95% CI) were estimated for the occurrence of IgG A. phagocytophilum antibodies.

Results: Of the total number of 181 people examined, 32 (17.7%) showed positive for IgG antibodies against A. phagocytophilum, 22 of whom were patients with suspected TBE (19.5%) and 10 people from control group (14.7%). The RR of occurrence of IgG A. phagocytophilum was 1.3-times higher in the patients with suspected TBE than in the control group.

Conclusion: None of the examined patients with suspected TBE had the disease confirmed. Hoever, as shown by the results, the relative risk of occurrence of anaplasmosis is higher in people examined for some another vector-borne disease (in this case TBE). Therefore, the performance of screening examinations in patients suspected of having any tick-borne disease is very important.