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Towards the Development of New Surveillance Approach of Tick Borne Encephalitis Virus
Date Issued |
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2021-06-16 |
no. 444332
Zoonotic Viruses: Clinical Virology
Tick-borne encephalitis (TBE) is recognized as the most important zoonotic tickborne viral disease in Europe. Causative agent of the disease is typically transmitted to human beings through bites of TBEV-infected ticks. However, alimentary infection after consumption of unpasteurized milk from domestic ruminants has previously been reported. In the present study we investigated a total of 2087 ruminant milk samples collected in 2018-2019 from systematically selected farms in various municipalities of Lithuania. All milk samples were collected once every four days from bulk tank throughout lactation period. Samples were analyzed by PCR using primers targeting NS5, NCR5 and E regions. Virus was isolated in Neuro-2a, Vero and MARC-145 cell lines and serial passages were performed to assess its viability to infect cells and obtain sufficient number of viral copies necessary for detection by molecular methods. Positive samples were confirmed by genome sequencing. Overall 4.54% [95% CI 3.54 – 5.53] of samples were positive for TBE virus. Spatio-temporal analysis showed majority of farms being affected by TBE causative agent, indicating widespread geographical distribution covering all major districts of the country. Farm and animal-level factors influencing the occurrence of the virus have also been identified. Simultaneously, ticks were collected in aforementioned municipalities by traditional flagging method, resulting in 0.37% [95% CI 0,14-0,76] of positive pools, which indicates ticks as potential source of animal infection. However, positive tick samples were located only in few endemic regions, which indicate milk sample usage as potential strategy for large scale monitoring of TBE virus.