[Show abstract][Hide abstract] ABSTRACT: Ticks were collected from the vegetation in the Baltic countries Estonia, Latvia, Lithuania and eastern Poland and analyzed for the presence of tick-borne encephalitis virus (TBEV) by amplification of the partial E and NS3 genes. In Estonia we found statistically significant differences in the TBEV prevalence between I. persulcatus and I. ricinus ticks (4.23% and 0.42%, respectively). In Latvia, the difference in TBEV prevalence between the two species was not statistically significant (1.02% for I. persulcatus and 1.51% for I. ricinus, respectively). In Lithuania and Poland TBEV was detected in 0.24% and 0.11% of I. ricinus ticks, respectively. Genetic characterization of the partial E and NS3 sequences demonstrated that the TBEV strains belonged to the European subtype in all countries, as well as to the Siberian subtype in Estonia. We also found that in areas where ranges of two tick species overlap, the TBEV subtypes may be detected not only in their natural vector, but also in sympatric tick species.
PLoS ONE 01/2013; 8(5):e61374. · 3.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The incidence of tick-borne encephalitis showed a dramatic spike in several countries in Europe in 2006, a year that was unusually cold in winter but unusually warm and dry in summer and autumn. In this study we examine the possible causes of the sudden increase in disease: more abundant infected ticks and/or increased exposure due to human behaviour, both in response to the weather.
For eight countries across Europe, field data on tick abundance for 2005-2007, collected monthly from a total of 41 sites, were analysed in relation to total annual and seasonal TBE incidence and temperature and rainfall conditions.
The weather in 2006-2007 was exceptional compared with the previous two decades, but neither the very cold start to 2006, nor the very hot period from summer 2006 to late spring 2007 had any consistent impact on tick abundance. Nor was the TBE spike in 2006 related to changes in tick abundance. Countries varied in the degree of TBE spike despite similar weather patterns, and also in the degree to which seasonal variation in TBE incidence matched seasonal tick activity.
The data suggest that the TBE spike was not due to weather-induced variation in tick population dynamics. An alternative explanation, supported by qualitative reports and some data, involves human behavioural responses to weather favourable for outdoor recreational activities, including wild mushroom and berry harvest, differentially influenced by national cultural practices and economic constraints.
[Show abstract][Hide abstract] ABSTRACT: Despite evidence that socio-economic factors associated with political transition played a major causal role in the abrupt upsurge in tick-borne encephalitis (TBE) in the newly independent Baltic States, doubts are still repeatedly expressed about the importance of these factors relative to changes in public health practices that may have affected merely the registration of cases. In response to these doubts, evidence of relevant practices of surveillance, registration, diagnosis, awareness and immunization is presented as taken from archived data and interviews with experienced medical practitioners. There were changes that could have had neutral, negative or positive impacts on recorded TBE incidence, but the variable timing in these changes at both national and regional levels is not consistent with their having been responsible for the epidemiological patterns observed in the early 1990 s.
Clinical Microbiology and Infection 01/2009; 15(1):75-80. · 4.58 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In Lithuania, 171-645 serologically confirmed cases of tick-borne encephalitis occurred annually [Mickiene et al. (2001): Eur J Clin Microbiol Infect Dis 20:886-888] in 1993-1999, and the tick-borne encephalitis virus (TBEV) seroprevalence in the general population was found previously to be 3.0% [Juceviciene et al. (2002): J Clin Virol 25:23-27]. To assess the risk for TBEV virus infection in Lithuania and to characterize the agent a panel of 3,234 ticks combined into 436 pools [Juceviciene et al., 2005] were tested for presence of TBEV RNA by a nested RT-PCR targeting at the NS5 gene. Six pools were confirmed positive and the prevalence of the infected ticks was 0.2% (if one tick per pool [Juceviciene et al., 2005] was considered positive) and the proportion of positive tick pools was 1.4%. The prevalence of the infected ticks in the Panevezys, Siauliai, and Radviliskis regions (in central Lithuania) was 0.1%, 0.4%, and 1.7% corresponding with a higher TBE disease burden in these regions. The 252-nucleotide NS5-region amplicons, and a longer sequence (737 nucleotides) obtained from one sample from the PrM-E gene region, were sequenced. Phylogenetic analysis of the latter showed that all western type TBEV PrM-E sequences, including the Lithuanian strains, were monophyletic, showed no clustering and had very little variation. The NS5 sequences, although identical within one locality, did not show any mutations common to strains from the two Lithuanian regions, nor could any geographical clustering be found among western type TBEV strains from other areas.
Journal of Medical Virology 11/2005; 77(2):249-56. · 2.37 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In order to obtain information about the distribution of tick-borne encephalitis virus (TBEV) in Lithuania, sera of domestic animals were screened for TBEV antibodies by haemagglutination inhibition test. Samples were collected in 2001 from 423 cows, 561 goats and 118 sheep during a prophylactic examination or vaccination by a local veterinary specialist. In addition, a total of 3234 Ixodes ricinus ticks in 436 pools were collected and tested by RT-PCR for the presence of TBEV RNA (detailed analysis with genetic characterization is published separately [Han et al, J Med Virol 2005 (in press)]). Domestic animal sera from 8/18 districts were positive with an overall seropositivity of 1.7% with considerable regional differences. Sheep from the Radviliskis region had the highest seropositivity rate (16%). In comparison, the proportion of tick pools positive for TBEV-RNA was 1.38%, ranging from 1.03% in Panavezys, 3.33% in Siauliai to 16% in Radviliskis.
[Show abstract][Hide abstract] ABSTRACT: Borrelia burgdorferi sensu lato, a tick-borne spirochete, is the causative agent of Lyme disease, the most prevalent vector-borne disease in Europe and United States. However, the incidence of this disease is variable and the clinical picture depends on the pathogen species. The infectivity of Ixodes ticks with Borrelia, was 46 % and 35 % in 2000 and 2001 in Latvia, respectively, and 14 % in 2002 in Lithuania, assessed by nested polymerase chain reaction (PCR) amplifi cation of the plasmid OspA gene fragment of Borrelia. PCR-restriction fragment length polymorphism (RFLP) analysis of the 16S-23S (rrs-rrlA) rRNA intergenic spacer was used for typing of Borrelia directly in ticks. Species-specifi c primers and subsequent sequences analysis were used as another approach for Borrelia species typing. All three clinically relevant B. burgdorferi sensu lato genospecies (B. afzelii, B. garinii, B. burgdorferi sensu stricto) were detected in the ticks collected in Latvia. The same result was obtained earlier in Estonia. B. valaisiana, a possible infectious agent of Lyme borreliosis, was detected only in Latvia. Only B. afzelii and B. garinii species were detected in ticks from Lithuania. Different subspecies were also identifi ed. This study demonstrates the predominance of the genospecies B. afzelii in all three Baltic countries, and the circulation of different B. burgdorferi sensu lato subspecies in the environment. This knowledge might have a signifi cant importance for monitoring of Lyme disease in Europe.