Page 343 - TBE_Book_V2_2019

Chapter 12b

TBE in Mongolia

Tserennorov Damdindorj, Uyanga Baasandagva,

Tsogbadrakh Nyamdorj and Burmaajav Badrakh

History and Current Situation

Already in the 1980s Mongolian scientists Seroprevalence against TBEV in human serum
worked together with researchers from the samples was 5.1% in the province of Selenge
21
Institute of Epidemiology and Microbiology of and 0.9% in Bulgan province.
Irkutsk, Russia to investigate the spread of
ticks carrying the TBEV in forest areas of The Selenge province was found to carry the
Khuvsgul, Khentii, Bulgan, Selenge, Orkhon, highest counts of I. persulcatus ticks frequent-
Central, Dornod, Arkhangai and Uvurkhangai ly infected with the TBEV. I. persulcatus ticks
provinces, which had been identified as TBE- were also found to be abun-dant in Bulgan,
1
endemic regions. Finally in 1989, following Tuv, Khuvsgul and Orkhon provinces of
5,6,9
available local information on diseases Mongolia. Human cases of TBE have been
suspected to be TBE, Abmed et al. document- officially registered at the national level since
ed natural foci of the TBEV in the cities of 2005. Between 2005-2017, 287 confirmed
Zelter, Bugant and Khuder in the Selenge cases have been documented in 63 cities of 15
province and noted that it is important to plan provinces (administrative units) and UB city.
2
and implement preventive measures. Most patients remembered a tick bite to have
occurred in the areas of Selenge (78%) or the
The physician of the city of Khuder in the Bulgan (12%) provinces. The overall TBE inci-
province of Selenge remembers that she had dence rate per 100,000 population increased
treated more than 400 patients with clinical five-fold in the last 3 years comparing the
signs of tick-borne encephalitis from 1993- previous 5-years (from 0.33 in 2010-2014 to
2000. Five of them had died and had been 1.73 in 2015-2017). During this period (2005-
recorded as „viral infections“. This is evidence 2017), there were 14 fatal cases (CFR 4.9%)
to indicate that TBE was first recorded at that attributed to severe meningoencephalitis
3
6
time. (Figure 1). In recent years (2014-2017) the
number of reported TBE cases and deaths
Between 1998-2005 population-based epi- increased annually. Also TBE cases have been
demiological surveillance detected 161 cases notified from areas without the main vector I.
of TBE in 18 cities and villages in 7 provinces, persulcatus and moreover the expansion of
including 90 cases of TBE, 65 cases of natural TBEV- foci is observed. 7,8,9,10,11
4
borreliosis, and 8 cases with dual infections.
In a seroprevalence study conducted before Vaccination against TBE has been consistently
2006, neutralizing antibodies against the TBEV carried out since 2005 in the risk areas of the
were only observed among residents of the country. 12,13,14 A molecular biological study of
northern parts of Mongolia, where the main TBEV was performed in collaboration with
vector, Ixodes persulcatus, is abundant. researchers from Germany and Russia and
determined the prevalent viral subtypes by
genetic sequencing. 7,15,16,17,18,19,20

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