[Investigation on the endemic foci of new emerged tick-borne encephalitis in Charles Hilary, Xinjiang].

Abstract

To investigate the recent emerged endemic region of tick-borne encephalitis (TBE) regarding its natural reserves, in Charles Hilary, northern Xinjiang and to isolate and characterize the viral geographic strain. Using indirect fluorescent assay to detect tick-borne encephalitis virus (TBEV) specific IgG antibodies from serum of local residents including 2 unconfirmed viral encephalitis patients in 2011 spring-summer. Viruses were isolated from tick samples by inoculating BALB/c mice and BHK-21 cells. For phylogenetic analysis. TBEV NS1 gene fragments were detected by RT-PCR and then subjected to sequence alignment. 1760 ticks were captured from the fields to have found that Ixodes persulcatus were dominated among the tick population. Two viral encephalitis patients were diagnosed as TBEV infection. In addition, 35.4% (23/65) local residents were detected positive for presence of TBEV specific-IgG antibodies in serum. After inoculation, morbidity and mortality of BALB/c mice were 72.9% (70/96) and 55.7% (44/79), respectively. TBEV specific-fragments were amplified from brain tissue of dead mice and cells culture supernatant. NS1 sequence alignment showed that the viral isolates were clustered into TBEV far-eastern sub-type, phylogenetically, and were mostly close to the isolates from northeastern China (99%) and Russian strain (98%). In this study, a new endemic loci of TBE was firstly described in Charles Hilary natural reserve, northern Xinjiang. TBEV geographic isolates belonged to TBEV far-eastern subtype while Ixodes persulcatus and Dermacentor silvarum played crucial roles for disease transition.