[The incidence of tularemia in Slovakia in 1997-2008]. / Výskyt tularémie na Slovensku v rokoch 1997-2008.

STUDY OBJECTIVE: Analysis of epidemiological trends in tularemia in the Slovak Republic (SR) over the last 12 years and changes in the epidemiology of this infection. MATERIAL AND METHODS: The sources of data for the epidemiological analysis are the SR annual tularemia surveillance report, records of epidemiological investigation of reported cases and knowledge from long-term surveillance of natural foci. The incidence of tularemia was analyzed based on the standard epidemiological indicators and in relation to infection sources and transmission routes. RESULTS: In 1997-2008, a total of 453 tularemia cases were reported from all administrative regions in Slovakia, the mean incidence was 0.71/10(5) population and 95.4% of cases were reported in the West, with the predominance of cases in the Nitra region where the mean incidence was 4/10(5) population. In the outbreak of 2002, the incidence of tularemia was as high as 18 cases/10(5) population. Tularemia cases were reported in all age groups and more than half of the patients were aged between 30 to 59 years. Tularemia cases were 1.9 times more frequent in males than in females. The seasonal trend peaked in summer, month of July. In a greater proportion of cases, 58.5%, the source of infection was other than brown hares, 16.3%, which correlates well with the decrease in the hare tularemia foci in the study period. The most frequent route of transmission was work exposure to contaminated animal feed and bedding and in an dusty environment with increased occurrence of small rodents. The proportion of tick-borne and biting insect-borne cases was 12.8% and 12.4% of cases were not elucidated epidemiologically. Clinical manifestations were ulceroglandular and glandular tularemia in 55.6%, pulmonary tularemia in 21.2 %, oroglandular tularaemia in 18.8% and other forms of tularaemia in 4.4%. CONCLUSION: The changes in the distribution of sources of infection and routes of transmission resulted in changed epidemiological characteristics and clinical forms of tularemia in Slovakia. The importance of tularemia surveillance is underlined.

Importance of surveillance of tularemia natural foci in the known endemic area of Central Europe, 1991-1997.

INTRODUCTION AND PURPOSE: Marked activation of natural foci of tularemia in the known endemic area of Central Europe, comprising the borderland of Slovakia, Austria and the Czech Republic, led to an epidemic outbreak in western Slovakia and an increase in the number of human tularemia cases in the adjoining regions of northeastern Austria and southern Moravia from 1995 to 1997. The aim of this paper was to present the results of a longitudinal study on the prevalence of infection with Francisella tularensis in small mammals and ticks in six localities of western Slovakia and northeastern Austria from 1991 to 1997, and to draw attention to the importance of systematic surveillance of natural foci for epidemiologic prognoses and for taking preventive measures. METHODS: In Slovakia, three localities of the Záhorie lowland were monitored for 3 to 6 years (1991 to 1996) for the presence of F. tularensis in small terrestrial mammals. In Austria, small mammals and ticks from three localities were investigated for 1 to 3 years (1994 to 1997). Spleens of live-trapped animals (at 1- to 2-month intervals) and ticks collected by flagging (in 6- to 8-week intervals) were examined by inoculation of pools into white mice, or individually by cultivation. RESULTS: In four localities under investigation (three localities in western Slovakia and one in Austria), a nearly simultaneous flare-up of tularemia epizootics was recorded in the autumn of 1994. The highest mean prevalence of infection in small mammals was 3.9% in the last quarter of the year, which along with isolations of F. tularensis from Dermacentor reticulatus ticks collected from vegetation in the locality of Austria (1.3% positivity), indicated the high epizootic activity of foci. F. tularensis was isolated from five rodent species--Apodemus flavicollis, A. sylvaticus, Clethrionomys glareolus, Microtus arvalis and Sorex araneus. From 1995 to 1996, the persistent activity of the focus was repeatedly confirmed by isolations of F. tularensis from D. reticulatus ticks. In 1995 a natural focus of tularemia was detected in a further locality of Austria, where the agent was isolated from D. reticulatus. The increased epizootic activity of foci in the endemic region of Central Europe indicated a higher risk of acquiring tularemia for humans and was, in fact, followed by an epidemic outbreak in western Slovakia as well as by a large number of cases in Austria and the Czech Republic. CONCLUSION: Our findings clearly demonstrate that long-term surveillance of natural foci in endemic regions provides useful information on the activation of tularemia foci before the onset of epidemic outbreaks, thus permitting timely epidemiologic prognoses and the institution of preventive measures.

Genetic diversity of Borrelia burgdorferi sensu lato isolates obtained from Ixodes ricinus ticks collected in Slovakia.

In Europe, Borrelia burgdorferi sensu lato is diverse, including B. burgdorferi s.s., B. garinii, B. afzelii, B. valaisiana and B. lusitaniae. In this study, we focused on the distribution of the different B. burgdorferi species among Ixodes ricinus adult ticks collected in an endemic area within Slovakia. We compared results of prevalence of B. burgdorferi infection in ticks obtained by immunofluorescence (IF) and by isolation. Isolates were characterized by restriction fragment length polymorphism (RFLP) of the rrf-rrl intergenic spacer genes using MseI. Using immunofluorescence we observed that 56/114 (49%) ticks were infected by B. burgdorferi s.l. Males were found to be more often infected (32/57, 56%) than females (24/57, 42%) but the difference was not significant (p = 0.1895). From the same 114 ticks a total of 37 isolates were obtained: 19 from males (33%) and 18 from females (32%). The RFLP identification revealed 25 B. afzelii (68%), 5 B. garinii (14%), 5 B. valaisiana (14%) and 2 B. lusitaniae (5%). The infection in ticks was more often detected by IF than by isolation (p = 0.0153) and isolation success was higher when the infection degree in ticks was high (p = 0.0397). The infection prevalence observed in this area is among the highest observed in Europe.

[A tularemia epidemic in western Slovakia 1995-1996]. / Epidémia tularémie na západnom Slovensku v rokoch 1995-1996.

The activation of natural foci of tularaemia in West Slovakia during 1994-1996 led to an epidemic outbreak in 1995-1996--mean annual morbidity 6.2 per 10(5) population. In comparison with the mean annual morbidity rate in the preceding period (1980-1994), a more than sevenfold increase was recorded. Of 213 notified cases of the disease 156 cases occurred in 1995--morbidity 8.9 per 10(5) population--being the highest morbidity recorded in this endemic region since the period of epidemic occurrence in the 60s. The highest proportion of cases (59.2%) was recorded in the districts of Nitra and Nové Zámky. The activation of natural foci along with changing social conditions, caused also marked changes of some epidemiological characteristics of tularaemia in Slovakia, such as seasonal and professional occurrence, as well as clinical forms of the disease. The impaired epidemiological situation in the occurrence of tularaemia is pointing to the importance of systematic surveillance to improve the diagnosis of the disease and ensure effective preventive measures.

Prevalence of ticks infected with Francisella tularensis in natural foci of tularemia in western Slovakia.

The prevalence of ticks infected with F. tularensis was followed during a systematic surveillance in endemic area of tularemia in western Slovakia over the years 1984-93. Ticks were collected from vegetation in localities of Podunajské Biskupice, in the vicinity of the capital of Slovakia, Bratislava, near the river Danube. In total 6033 ticks, mostly adults of Dermacentor reticulatus and Ixodes ricinus (4994 and 1004, respectively) and 35 nymphs of Haemaphysalis concinna, were examined for the presence of F. tularensis. Out of 4542 starving ticks, 34 F. tularensis strains were isolated predominantly from D. reticulatus (30), and to a smaller extent also from I. ricinus (3) and H. concinna (1). Natural infection with F. tularensis was further proved from 1491 adults of D. reticulatus fed on laboratory animals, rabbits and white mice, together in 27 cases. From that, 21 times it was by positive isolation either from suspensions of partly or fully engorged ticks and their feaces, or from spleens of animals dead after the feeding of ticks. In addition, solely the development of antibodies against the agent was confirmed in 6 rabbit hosts. The presence of F. tularensis in all the above mentioned tick species and namely the relatively high and permanent infestation of D. reticulatus adults, ranging between 0.5-2% during the followed time period, demonstrated the maintenance of active natural focus of tularemia in the area under study. The present paper also emphasizes the epidemiologic consequence of various species of ticks in endemic foci of tularemia and the aspect of possible ways of transmission of the agent to humans.

[Transstadial transmission of Francisella tularensis by Ixodes ricinus ticks infected during the nymphal stage]. / Transstadiálny prenos Francisella tularensis u kliest'ov Ixodes ricinus infikovaných v stádiu nymfy.

The degree of infection of nymphs of Ixodes ricinus which finished their feeding on experimentally infected mice on the day of their death from tularaemia represented more than 10(7) cells of Francisella tularensis per tick after feeding. The high degree of positivity was preserved in ticks also during one month of metamorphosis. Transstadial transmission of the agent from the stage of nymph to the stage of imago was confirmed in adults either by cultivation or by experiments attempting to transmit the infection to white mice, even after more than a year after infection of nymphs or more than a year after metamorphosis. Some of the ticks which did not transmit the infection while feeding were found to be positive subsequently. Results of quantitative examination of the degree of infection indicate also the possibility of reproduction of the agent in imagines after feeding on hosts. Incompletely engorged nymphs which fed repeatedly on mice after being collected from their host dead from tularaemia, were able to transmit the infection during interrupted feeding. Further possibilities of transmission were indicated by findings of consumption of infected ticks by hosts or by elimination of F. tularensis in faeces of infected nymphs and adults.

[An unusual finding on the eyelid]. / Prekvapujúci nález na mihalnici.

The authors describe an unusual case of tick on the patient's eyelid. The ophthamologist considers the case as being benign. From the epidemiologic point of view it is necessary to consider the possibility of transmission of some infectious diseases by this mode. Ticks transmit the early summer meningocephalitis and Lym borreliosis. (Ref. 4.)

[Transstadial transmission of Francisella tularensis in the tick, Ixodes ricinus, infected during the larval stage]. / Transstadiálny prenos Francisella tularensis u kliest'ov Ixodes ricinus infikovaných v stádiu larvy.

Based on previous studies which proved the decisive importance of the degree of bacteraemia of experimentally infected white mice for the degree of infection of ticks Ixodes ricinus the authors confirmed the possibility of transstadial transmission of Francisella tularensis from larvae via nymphs to imagos by the detection of germs in the ticks and by experiments attempting their transmission to white mice. This applied to imagos even one year after the infection of larvae. Transmission was recorded even in imagos which did not transmit the infection in the nymphal stage. F. tularensis was repeatedly detected in the faeces of nymphs and imagos, which along with possible consumption of infected ticks by hosts, indicates further possibilities of transmission of the infection in nature. The results of quantitative examinations of the degree of infection of ticks enable us to conclude that the germs reproduce in the ticks after feeding on the host.

Tick-borne encephalitis virus activity in Styria, Austria.

From 3,404 Ixodes ricinus ticks collected in 12 localities of Styria, Austria in 1990, 15 tick-borne encephalitis (TBE) virus isolates were recovered. Minimal field infection rate reached 4.4 virus containing ticks out of 1,000 collected ticks. Five isolates of TBE virus were obtained from target organs of Apodemus flavicollis trapped in locality Wagnitz. In a serosurvey based on virus neutralizing antibodies high prevalence of TBE virus was demonstrated in A. flavicollis (47.9%) and Clethrionomys glareolus (29.4%). These rodents formed 57.8% and 41.0% of 83 trapped small mammals.

[Relation between the level of infection in Ixodes ricinus with Francisella tularensis and the level of bacteremia in the host]. / Závislost' stupna infikovanosti kliest'ov Ixodes ricinus Francisellou tularensis na stupni bakteriémie hostitel'a.

The dynamics of bacteremia on white mice subcutaneously infected with an inoculum of 100 and 10 cells of F. tularensis (strain 273) was compared in two parallel experiments. The rise of bacteremia was relatively uniform, about 3 logarithms a day in both groups of animals, so that it reached values of 10(9)-10(10) cells per 1 ml of blood ante finem. Larvae of Ixodes ricinus were fed on white mice in different stages of bacteremia, so that groups of ticks with different degrees of infection were obtained. Our results of quantitative examination show an evident correlation between the degree of bacteremia of the host and the degree of infection of ticks. The highest values of positivity 10(6)-10(7) cells were recorded in larvae, which finished their feeding on the day of the host's death, during the time when bacteremia was reaching the highest degree 10(10) cells per ml of the blood. Persistence of the agent in the organism of infected larvae could be observed up to hatching, under given experimental conditions one month after infection. In nymphs developed from larvae with the highest degree of infection this ability was preserved in about one third of individuals still after 5 months of starvation. In ticks with low degrees of infection it disappeared during the experiments.

[Infestation of ticks with Borrelia burgdorferi and Francisella tularensis in Slovakia]. / Stúdium premorenosti kliest'ov Boréliou burgdorferi a Francisellou tularensis na Slovensku.

Examination of ticks for the presence of F. tularensis resulted in the isolation of 29 strains, predominantly from the species D. reticulatus (19x), further from I. ricinus (8x) and from H. concinna (2x). The results confirmed the activity of the known endemic focus in the area of Podunajské Biskupice and revealed three new foci in the localities Smolenice (district of Trnava), Olichov (district of Nitra), and Plást'ovce (district of Levice). In the focus of Podunajské Biskupice the mean infestation of ticks of the species D. reticulatus was around 1.4% over the years of investigation. With regard to the one-year developmental cycle, D. reticulatus can be considered an appropriate indicator of current epizootic activity of the focus, while the occurrence of I. ricinus is rather an indicator of the geographic spread of foci. The third part of the study addresses questions of the ecology of ticks. It analyzes their biological characteristics in our conditions, their spread and bionomy, particularly from aspects related with their epidemiological significance as vectors of Lyma borreliosis and tularemia. Systematic follow up of infestation of ticks with causative agents of borreliosis and tularemia in established endemic foci as well as in epidemiologically indicated localities is an inevitable part of modern surveillance of these infections.

Investigations of ticks for the presence of Borrelia in Czechoslovakia.

More than 570 ticks from different parts of the country were studied microscopically. In 45 cases (8%) Borreliae were found. The infectivity rate of ticks in different foci varied from 3-11%, in some instances nearly 20%. Only Ixodes ricinus, male and female ticks were positive in this study.

Isolation of Francisella tularensis from mites Haemogamasus nidi and Laelaps hilaris in western slovakia.

Isolating of F. tularensis from gamasid mites H. nidi parasitizing on the bank vole (Cl. glareolus) and L. hilaris on the common vole (M. arvalis) are reported. The epidemiological significance of this finding is discussed.