Characterization of tick-borne encephalitis virus in Kazakhstan by serological and molecular-biological techniques

Shin, Anna (2023): Characterization of tick-borne encephalitis virus in Kazakhstan by serological and molecular-biological techniques. Dissertation, LMU München: Medizinische Fakultät

Abstract

Tick-borne Encephalitis virus (TBEV), leading to one of the most dangerous neuroviral infection in humans named Tick-Borne Encephalitis (TBE) and West Nile fever virus that is a cause of neurotropic infection West Nile fever (WNF) are both belonging to the viral family of flaviviruses.In the Republic of Kazakhstan only limited data about TBEV, TBE and WNFV are available. In the last ten years 348 cases of TBE were registered but they are based on unreliable serological investigations. Furthermore, in 400 cases between 2017-2019 the aetiological agent of serous meningitis could not be determined and hence they were declared as cases of serous meningitis with unknown origin. TBEV is transmitted by ticks and up to date there is hardly any information about the rate of infected ticks in Kazakhstan. The presence of WNFV in the Republic of Kazakhstan was confirmed in mosquitos and by the presence IgG specific antibodies in human sera in West Kazakhstan. However, there is no official registration of WNF cases or monitoring of mosquitos and/or birds as vectors.The similarity of the antigenic structure of the members of the flavivirus leads to the need for reliable diagnostic meth-ods to discriminate between these pathogens. In our study we investigated three regions of Ka-zakhstan with TBE cases that are East Kazakhstan Oblast, Almaty and Akmola Oblast including 166 sera and 130 cerebrospinal fluid (CSF) samples from patients with meningitis symptoms. In addition, participants needed to answer a questionnaire with focus on socio-demographic factors, travel history, contact to animals and vectors, tick bites, vaccination status and clinical symptoms to understand more about the mode of infection. All samples were tested for flaviviruses by screening for IgG and IgM antibodies in an ELISA, an immunofluorescence assay using a flavivirus biochip and a TBEV specific real-time RT-PCR. Our findings show TBEV and WNFV antibodies in 31 samples. In Kazakhstan also only limited data on the phylogenesis of TBEV is available. Hence, TBEV in its tick vector was also investigated in our studies. In more than 10,000 screened ticks from the three regions 0.5% of pools were found to be positive for TBEV using a specific real-time RT-PCR. Phylogenetic analysis of gained sequences showed the Siberian subtype of TBEV to be predominant in Kazakhstan. In this study, we present a broad investigation of the spread of TBEV in Kazakhstan in humans and also in ticks. Our results have an impact on diagnostic algorithms in Kazakhstan and medical doctors should be aware of TBEV and WNFV to play a role in meningeal diseases of unknown origin in the Republic of Kazakhstan.

• Dokumententyp: Dissertationen (Dissertation, LMU München)
• Keywords: Zoonosis, Tick-borne encephalitis virus, West Nile Fever virus, meningitis, serology, tick, Siberian subtype
• Themengebiete: 600 Technik, Medizin, angewandte Wissenschaften ; 600 Technik, Medizin, angewandte Wissenschaften > 610 Medizin und Gesundheit
• Fakultäten: Medizinische Fakultät
• Sprache der Hochschulschrift: Englisch
• Datum der mündlichen Prüfung: 20. Januar 2023
• 1. Bericht­erstatter:in: Hoelscher, Michael