**3. Tikc-borne viral encephalitis**

#### **3.1. TBVE Epidemiology**

Virological surveillance, that has been conducted by scientists of the laboratory of Transmis‐ sible Viral Infections (TVI) of State Institution "Lviv Research Institute of Epidemiology and Hygiene Ministry of Health of Ukraine" (LRIEH), enabled detection of 38 strains of TBVE virus. Most of them (26 strains) were isolated from *I. ricinus* ticks, whose rates of TBVE infection in active natural foci are 19,5 %, from mouse-like rodents (*Apodemus аgrarius*, *A. sylvaticus*) – 2 strains, from birds (*Fulica atra*) – 1 strain and from TBVE patients – 9 strains.

Due to their antigen characteristics, strains of TBE virus isolated in Ukraine belong to ricinusserotype (genotype 2) and have almost same biological characteristics as causative agent of Central-European encephalitis of countries of Eastern and Western Europe [3, 4].

For 2011 enzootic as to TBVE territories, distinguished according to one or combination of such characteristics as natural infection (presence of antigen) of ixodid ticks and small mammals (potential carriers and reservoirs of pathogen) with causative agent, diagnosed cases of the disease with local infection, high degrees of population immunity, were registered in 33 settlements of 9 districts of Volyn oblast [5] (fig.1).

**Figure 1.** Shematic map of TBVE enzootic territories in Volyn oblast

The main reservoirs of TBVE virus in nature are *Microtus arvalis*, *Myodes glareolus*, and *Apodemus agrarius,* where the part of *M. arvalis* makes more than 50 %.

Among ixodid ticks, the species which are more often infected with TBE virus are *Dermacentor reticulatus* (64,3 %), while among the *Ixodes ricinus* this number is 35,7% [6].

#### **3.2. TBVE incidence rates**

south it borders with Lviv oblast, on the east with Rivne oblast, on the north with the Republic

Climate of Volyn oblast is mild-continental, with mild winters, short periods of freezing, frequent thaws, mild summers, without significant heat waves, heavy percipitation, long springs and autumns. Average January temperature is +4,5 ⁰C, for July it is +18,6 ⁰C. Vegetation period lasts for about 200 days. The sums of the temperatures for the periods with stabile temperatures above +10, make 2495-2580 ⁰C. Percipitation makes 550-600 mm a year. Relative humidity of the air is in the reverse proportion to its temperature: in the winter it exceeds 80

Territory of Volyn oblast is the part of Eastern-European province of broadleaf forests of the European Broadleaf Zone. The landscapes of the zone are of two types: Polissya, with high prevalence of swamps, meadows, oak-pine and narrow-leaf forests and Forest-Steppe type zone, with prevalence of meadow steppes and oak-hornbeam forests in prehistoric times,

Due to its zoo-geographic parameters, Volyn oblast is a borreal-forest zoo-geographic type of zone. Its territory hosts 301 vertebral species, among them 183 species of nesting and nonmigrating birds, 64 species of mammals. Among small mammals, which are within the range of parasitory system of tick-borne infections, there are *Sorex araneus*, *Castor fiber*, *Аpodemus agrarius*, *Arvicolla terrestris* (*amphibious*), *Microtus oeconomus*. To woods species belong *Sciurus vulgaris*, *Microtus subterraneus*, *Meles meles*. In zoocenozes also are distributed *Dryomys nitedula*, *Glis glis*, *Muscardinus avellanarius*, *Myodes Clethrionomys glareolus*, *Sylvaemus sylvaticus, Sylvaemus tauricus, Talpa europaea, Erinaceus europaeus* [2]. All territory of the oblast is within

The findings of the complex studies and surveillance, conducted in the period of 1990-2011, showed the presence of active natural foci of TBVE and ITBB on the considerable part of the

**Aims of study:** to look at the incidence rates of tick-borne infectious diseases and analyse the range of their clinical manifestations in north-west region of Ukraine taking Volyn oblast as a

Virological surveillance, that has been conducted by scientists of the laboratory of Transmis‐ sible Viral Infections (TVI) of State Institution "Lviv Research Institute of Epidemiology and Hygiene Ministry of Health of Ukraine" (LRIEH), enabled detection of 38 strains of TBVE virus. Most of them (26 strains) were isolated from *I. ricinus* ticks, whose rates of TBVE infection in active natural foci are 19,5 %, from mouse-like rodents (*Apodemus аgrarius*, *A. sylvaticus*) – 2

strains, from birds (*Fulica atra*) – 1 strain and from TBVE patients – 9 strains.

the area of *I. ricinus* ticks - main vector of tick-borne pathogenes in Europe.

of Belarus, on the west (along the Western Bug) with Poland.

%, in the summer it reaches 65-70 % [1].

146 Encephalitis

which are mainly farming lands nowadays.

sample territory during the period of 1990-2011.

**3. Tikc-borne viral encephalitis**

territory of the oblast.

**3.1. TBVE Epidemiology**

Tick-borne viral encephalitis is one of the most prevalent arboviral infections in Ukraine. People get infected with it through the tick bite or by consuming raw, mainly goat milk.

For present moment local cases of TBVE among people are registered yearly in 16 out of 25 oblasts of Ukraine, in cities Kyiv and Sevastopol. However the official data don't reflect the real state of things with the morbidity in Ukraine [7].

During the period of 1955 to 2010 there were only 580 TBVE cases registered, while 132 of them were registered in the period of 2000–2011 (fig. 2). And correspondingly, the indices of morbidity in Ukraine during the decade varied in the range 0,001 – 0,03/100 000 population, including per oblast from 0–1,5 [8].

During the period of 2003-2010 we observed 223 cases of seroconversion in diagnostic titers of people from 14 oblasts of Ukraine. Among them in Volyn oblast - 77 cases [9].

**Figure 3.** The main clinical forms of TBVE in Volyn oblast

by author as"attenuate TBVE" [12].

differ significantly (P>0,05).

and Lutsk districts [13].

patients with poliomyelitic –like form of a disease.

Clinical manifestations are similar to the western type of this infection, but there predominated one-wave character of thermal curve, while two-wave type of fever and changes in hemogram were observed in half frequency. The temperature curve of part of the patients had three waves. In terms of neurological complaints there predominated the vertigo, walk unsteadiness, bones and lips tremor. Sensitivity disorders in forms of paresthesia were common as well. From the side of vegetative nervous system during the acute period the leading symptoms were the following: bradycardia, growth of blood pressure, clearly manifested hyperhidrosis, stable diffuse dermographism. In the acute period of the disease some patients developed thyroid enlargement, asymmetry of skin temperature. Highly notable were various "pseudonevras‐ thenic" complaints which followed the course of the disease: memory decrease, irritability, obsessive fears and thoughts, emotional lability. The before-mentioned clinical form was called

Active Natural Foci of Tick-Borne Neuroinfections in the North-West Region of Ukraine

http://dx.doi.org/10.5772/54912

149

Almost half of patients (48,2 %) – the initial stage of the disease was characterized by some prodromal indications, manifestation of which wasn't pathognomonic for the given disease. As a result of a transmissible form of infection (P<0,05), there were more complicated mani‐ festations of it, when in terms of clearly manifested intoxication and general-cerebral syn‐ drome, changes from the side of a nervous system there developed a disfunction of a vegetative nervous system which prevailed in different parts of it (P<0,05), there were observed patho‐ logic indications in cardio-vascular system (P<0,05), liver enlargement (P<0,001). All disorders of a vegetative nervous system were of central genesis as a rule, and developed mainly as a result of more considerable lesions of a central nervous system. As a common indication there was observed a skin hyperhidrosis, especially of a local character, which developed in all

It has to be mentioned that the rates of TBVE forms with the lesions of a central nervous system which followed the tick bites and those which followed the alimentary way of infection didn't

We found that TBVE area includes Ratne and some more districts, which is confirmed by new cases reported, positive results of TBVE antigen screening in *Ixodid* ticks and rodents, and positive immune layer among healthy population in Kivertsi, Kovel, Rozhysche, Lyuboml,

**Figure 2.** Cases of TBVE in Ukraine (1990-2011)

On the territory of Volyn oblast on the whole, there were 187 cases of TBVE reported. This is almost third of all reported cases for Ukraine (32,5 %).

Within the range of natural foci described, the TBVE morbidity is characterized by a sporadic occurance, its clinical course is similar to western noso-geographic form of the disease. The considerable part of foci forms of TBVE was reported from Ukrainian Polissya (Volyn, Zhytomyr and Kyiv oblasts) [10].

The most active natural TBVE foci, which manifested itself with group morbidity, was detected in Ratne district of Volyn oblast. It was confirmed by isolation of TBVE virus strains from *I. ricinus* ticks and results of antigen screening in *D. reticulatus*, *I. ricinus* and body organs of *Apodemus agrarius*.

During the period of April-October 1995, there were more than 80 patients hospitalized, with fe‐ ver, and the air-ways and central nervous system lesions. The largest part of cases was reported during the period of June-September, which is related to the berries-mushrooms season.

The largest part of cases appeared in residential areas that are in the close proximity to the forests and is caused by tick bites.

The disease was registered in spring-autumn period, starting in May and ending in November, with the peak in July-August. The main means of infection was transmitting (68,0 %). The cases of alimentary infection with TBVE (32,0 %) were due to a consumption of raw goat and cow's milk and its products. The development of a severe and complicated clinical forms of a disease was more common in terms of the transmitting way of infection (P<0,05).

In general TBVE in Volyn is characterized by one-wave feverous period, with predomination of feverous (60 %) and meningeal (24 %) forms of a disease with only 16 % of focal form (fig. 3), coordination disorders, insignificant quantity of paralytic forms and cases of a development of a chronic disease.

**Figure 3.** The main clinical forms of TBVE in Volyn oblast

morbidity in Ukraine during the decade varied in the range 0,001 – 0,03/100 000 population,

During the period of 2003-2010 we observed 223 cases of seroconversion in diagnostic titers of

people from 14 oblasts of Ukraine. Among them in Volyn oblast - 77 cases [9].

including per oblast from 0–1,5 [8].

*Apodemus agrarius*.

of a chronic disease.

no of cases

148 Encephalitis

1990

1991

1992

**Figure 2.** Cases of TBVE in Ukraine (1990-2011)

Zhytomyr and Kyiv oblasts) [10].

forests and is caused by tick bites.

1993

1994

almost third of all reported cases for Ukraine (32,5 %).

1995

1996

1997

1998

1999

2000

On the territory of Volyn oblast on the whole, there were 187 cases of TBVE reported. This is

Within the range of natural foci described, the TBVE morbidity is characterized by a sporadic occurance, its clinical course is similar to western noso-geographic form of the disease. The considerable part of foci forms of TBVE was reported from Ukrainian Polissya (Volyn,

The most active natural TBVE foci, which manifested itself with group morbidity, was detected in Ratne district of Volyn oblast. It was confirmed by isolation of TBVE virus strains from *I. ricinus* ticks and results of antigen screening in *D. reticulatus*, *I. ricinus* and body organs of

During the period of April-October 1995, there were more than 80 patients hospitalized, with fe‐ ver, and the air-ways and central nervous system lesions. The largest part of cases was reported

The largest part of cases appeared in residential areas that are in the close proximity to the

The disease was registered in spring-autumn period, starting in May and ending in November, with the peak in July-August. The main means of infection was transmitting (68,0 %). The cases of alimentary infection with TBVE (32,0 %) were due to a consumption of raw goat and cow's milk and its products. The development of a severe and complicated clinical forms of a disease

In general TBVE in Volyn is characterized by one-wave feverous period, with predomination of feverous (60 %) and meningeal (24 %) forms of a disease with only 16 % of focal form (fig. 3), coordination disorders, insignificant quantity of paralytic forms and cases of a development

during the period of June-September, which is related to the berries-mushrooms season.

was more common in terms of the transmitting way of infection (P<0,05).

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

Clinical manifestations are similar to the western type of this infection, but there predominated one-wave character of thermal curve, while two-wave type of fever and changes in hemogram were observed in half frequency. The temperature curve of part of the patients had three waves.

In terms of neurological complaints there predominated the vertigo, walk unsteadiness, bones and lips tremor. Sensitivity disorders in forms of paresthesia were common as well. From the side of vegetative nervous system during the acute period the leading symptoms were the following: bradycardia, growth of blood pressure, clearly manifested hyperhidrosis, stable diffuse dermographism. In the acute period of the disease some patients developed thyroid enlargement, asymmetry of skin temperature. Highly notable were various "pseudonevras‐ thenic" complaints which followed the course of the disease: memory decrease, irritability, obsessive fears and thoughts, emotional lability. The before-mentioned clinical form was called by author as"attenuate TBVE" [12].

Almost half of patients (48,2 %) – the initial stage of the disease was characterized by some prodromal indications, manifestation of which wasn't pathognomonic for the given disease. As a result of a transmissible form of infection (P<0,05), there were more complicated mani‐ festations of it, when in terms of clearly manifested intoxication and general-cerebral syn‐ drome, changes from the side of a nervous system there developed a disfunction of a vegetative nervous system which prevailed in different parts of it (P<0,05), there were observed patho‐ logic indications in cardio-vascular system (P<0,05), liver enlargement (P<0,001). All disorders of a vegetative nervous system were of central genesis as a rule, and developed mainly as a result of more considerable lesions of a central nervous system. As a common indication there was observed a skin hyperhidrosis, especially of a local character, which developed in all patients with poliomyelitic –like form of a disease.

It has to be mentioned that the rates of TBVE forms with the lesions of a central nervous system which followed the tick bites and those which followed the alimentary way of infection didn't differ significantly (P>0,05).

We found that TBVE area includes Ratne and some more districts, which is confirmed by new cases reported, positive results of TBVE antigen screening in *Ixodid* ticks and rodents, and positive immune layer among healthy population in Kivertsi, Kovel, Rozhysche, Lyuboml, and Lutsk districts [13].
