TBE in Belarus

Volha Kniazeva, Wilhelm Erber and Tamara Vuković-Janković

E-CDC risk status: endemic

(data as of end 2022)

History and current situation

Belarus is a landlocked country of eastern Europe with a population of 9.4 million, of which 78.4% reside in urban areas bordered by Lithuania and Latvia to the north west, by Russia to the north and east, by Ukraine to the south, and by Poland to the west. The country of Belarus is divided into six administrative districts (Brest, Gomel, Grodno, Minsk, Mogilev, Vitebsk regions) each centered around a major city (Minsk). Much of the country consists of flat lowlands separated by low-level topped hills and uplands; the highest point is Dzyarzhynskaya Hill, being only 1135 feet (346 meters) above sea level. Over half of the surface area of Belarus lies below 660 feet (200 meters), and about 40% of the country is forested. The most common tick species in Belarus are Ixodes ricinus and Dermacentor reticulatus.1-3

Almost the entire territory of Belarus is believed to be endemic for tick-borne encephalitis virus (TBEV), with the Central European subtype, also known as TBEV-EU (Figure 1). In all, 96 counties (i.e., 71.5% of all administrative districts) are considered to be risk areas for tick-borne encephalitis (TBE).1 The most intensive natural foci have been found in the western part of the country Tick-borne encephalitis virus circulation is detected in 15 out of 16 administrative territories of Brest region, among which 5 districts are defined as endemic (where the disease has been formed and maintained for a long period of time): Berezovsky, Ivatsevichy, Kamenetsky, Malorita and Pruzhany districts, and most of administrative territories of Grodno region.4

Figure 1: Administrative territories of the Republic of Belarus where circulation of tick-borne encephalitis virus (TBEV/VTBE) causal agents were identified, 1998–20075

Click the image above to enlarge

To determine whether or not changes in the TBEV infection rates in ticks followed a trend over time, joinpoint regression was estimated for annual percentage of infected ticks group by using the Joinpoint Trend Analysis Software, Version 4.5.0.1 (Statistical Research and Applications Branch, National Cancer Institute; https://surveillance.cancer.gov/joinpoint/). Same analysis was performed for TBE incidence of population of Belarus.

In brief, by using the TBE incidence rate per 100 000 and population of Belarus data for TBE and annual percentage of infected ticks rate data for TBEV in the transmitters as inputs, this method identifies the year(s) when a trend change occurs. One can therefore calculate the annual percentage change (APC) in rates between trend-change points, and also estimate the average annual percentage change (AAPC) in the whole period studied (Figure 2).6-7

To estimate the APC, the following model was used:

where log (Yx) is the natural logarithm of the rate in year x.

Then, the APC from year x to year x + 1 is:

When there are no join points (i.e., no changes in trend), APC is constant, so it equals the AAPC.2-3

 

Figure 2: Joinpoint regression model of TBEV in ticks in Belarus, 2012-2020

Click the image above to enlarge

Source data –
ObservedModeled Crude Rate
20129.89.55
201319.89.66
2014159.78
20151.69.9
20169.410.03
201716.710.15
20188.710.28
201915.810.4
202010.210.53
SegmentLower EndpointUpper EndpointAPCLower ClUpper ClTest Statistic (t)Prob > |t|
1201220201.2-20.729.20.10.9
*Indicates that Annual Percent Change (APC) at significantly different from zero at a=0.05

In the decades from 2000 to 2020, the number of registered human TBE cases ranged from 18 in 2002 (incidence rate, 0.2 per 100,000) to 171 in 2019 (1.8 per 100,000). Overall, 1912 cases were registered in that period, which corresponds to a mean annual case number of 91. Figure 3 displays the increasing trend of TBE incidence by 6.41% every year that was significantly different from zero at a = 0.05. (Figure 3).8

 

Figure 3

Click the image above to enlarge

Source data –
YearNumber of CasesIncidence / 105
2000230.2
2001610.64
2002180.2
2003530.5
2004440.4
2005460.5
20061081.1
2007820.8
2008660.7
2009880.9
2010911
20111081.1
20121221.3
20131091.2
20141191.3
2015770.8
20161411.5
20171421.5
20181351.4
20191711.8
20201081.1
20211081.17
2022No data
SegmentLower EndpointUpper EndpointAPCLower ClUpper ClTest Statistic (t)Prob > |t|
1200020206.4^4.18.85.90
*Indicates that Annual Percent Change (APC) at significantly different from zero at a=0.05

Given the presence of high numbers of TBEV-infected ticks, the number of reported cases appears to be low and the true burden of TBE is likely underestimated.

Children aged 7–14 years represented 10%–15% of the total number of TBE cases.5

Two alimentary outbreaks have been reported, one in 2006 and one in 2007, with a total number of 16 persons infected.5

Overview of TBE in Belarus

Table 1: Virus, vector, transmission of TBE in Belarus
Viral subtypes, distribution Central European subtype (TBEV-EU) has been detected in almost the entire country.5
Reservoir animals Information not available
Infected tick species (%) In Belarus the main vectors for TBE are Ixodes ricinus and Dermacentor reticulatus.5
Since 2005, surveillance of TBE in ticks started. A medium direct correlation was established (r = 0.7 with Р ≤ 0.05) between the incidence rate of tick-borne encephalitis and the natural foci intensity rate.
Dairy product transmission Cases of alimentary TBE 2006–2007: 16 cases reported due to the consumption of raw goat milk.5

 

Table 2: TBE reporting and vaccine prevention in Belarus
Mandatory TBE reporting Registration of people with tick bites seeking medical advice and/or primary diagnosis of TBE according to clinical signs and epidemiological anamnesis. From counties, reports are sent to higher healthcare organizations.
Other TBE surveillance No information available
Special clinical features Biphasic disease
Available vaccines EnceVir, TBE vaccine Moscow4
Vaccination recommendations and reimbursement Recommended for high-risk population living in endemic areas
Vaccine uptake by age group/risk group/general population Information not available
Name, address/website of TBE National Reference Center Republican Centre of Hygiene, Epidemiology and Public Health (Ministry of Health) of Belarus http://rcheph.by/en/

 

Figure 4: Burden of TBE in Belarus over time

Click the image above to enlarge

Source Data:
YearNumber of CasesIncidence / 105
2000230.2
2001610.64
2002180.2
2003530.5
2004440.4
2005460.5
20061081.1
2007820.8
2008660.7
2009880.9
2010911
20111081.1
20121221.3
20131091.2
20141191.3
2015770.8
20161411.5
20171421.5
20181351.4
20191711.8
20201081.1
20211081.17
2022No data

Age and gender distribution of TBE in Belarus:

No data available

TBEV-isolation in Belarus:

No data available

Contact:

olgaknyazzeva@gmail.com

Citation:

Kniazeva V, Erber W, Vuković-Janković T. TBE in Belarus. Chapter 12b. In: Dobler G, Erber W, Bröker M, Schmitt HJ, eds. The TBE Book. 6th ed. Singapore: Global Health Press; 2023. doi: 10.33442/26613980_12b2-6

References

  1. Krasko A, Kniazeva V, Scheslenok E, Semizon P, Vedenkov A, et al. Pathogenic microorganisms in Ixodes ricinus ticks collected in Belarus. Medical virology, Moscow. 2013, ХХVII (1) (article in Russian)
  2. Kniazeva V, Pogotskaya Y, Higgs S, Krasko A. The Prevalence of Different Human Pathogenic Microorganisms Transmitted by Ixodes Tick Vectors in Belarus. Vector Borne Zoonotic Dis. 2021 Jan;21(1):6-10.
  3. Reye AL, Stegniy V, Mishaeva NP, Velhin S, Hübschen JM, et al. Prevalence of Tick-Borne Pathogens in Ixodes ricinus and Dermacentor reticulatus Ticks from Different Geographical Locations in Belarus. PLOS ONE. 2013;8(1): e54476.
  4. http://brest-region.gov.by/index.php/glavnaya/241-oblast/obshchestvo/zdravookhranenie/zdorovyj-obraz-zhizni/publikatsii/8103-profilaktika-transmissivnykh-infektsij
  5. Karaban I, Vedenkov A, Yashkova S, Sebut N. Epidemiology of tick-borne encephalitis and Lyme disease in the Republic of Belarus, 1998-2007. EpiNorth. 2009;10:48–57. [Google Scholar]
  6. Radzisauskiene D, Zagminas K, Asokliene L, et al. Epidemiological patterns of tick-borne encephalitis in Lithuania and clinical features in adults in the light of the high incidence in recent years: a retrospective study. European journal of neurology: the official journal of the European Federation of Neurological Societies. 2018;25(2):268-274.
  7. Dragomirescu I, Llorca J, Gómez-Acebo I, Dierssen-Sotos T. A join point regression analysis of trends in mortality due to osteoporosis in Spain. Scientific reports. 2019;9(1):4264.Krotkova EN. et al. Epidemiological and clinical features of tick-borne encephalitis in north-western region in Belarus. Przegl Epidemiol. 2016;70(3):436-43.
  8. Public health in the Republic of Belarus An official statistics collection, 2005-2019. https://www.belstat.gov.by/en/ofitsialnaya-statistika/
  9. Kollaritsch H, Krasilnikov V, Holzmann H, et al. Background Document on Vaccines and Vaccination against Tick-borne Encephalitis (TBE). Geneva, WHO Strategic Advisory Group of Experts on Immunization. Available at: http://www.who.int/immunization/sage/6_TBE_backgr_18_Mar_net_apr_2011.pdf. [Accessed: June 2017].

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