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Leptospirosis is a typical zoonosis with natural nidalily, and its occurrence in the climatic conditions of the Czech Republic is sporadic, with a normal incidence of about 0.3 cases per 100000 inhabitants. In 1997 and 2002, however, the incidence of leptospirosis has been influenced by natural phenomena, catastrophic floods, which increased the numbers of serologically diagnosed and registered cases three times. In 1997 a total of 7156 subjects in the Czech Republic were examined for a leptospirosis, and the disease was diagnosed and registered in 94 of them.

Present risk assessment and prediction of future risk of humans exposed to Ixodes (I.) ricinus tick attacks and, consequently, to tick-borne encephalitis (TBE) virus infection as one of the basic preconditions for successful TBE prevention has been intensively studied in the Czech Republic. An atlas of TBE in the Czech Republic containing predictive maps of I. ricinus high-incidence habitats and TBE risk sites identified by satellite data (Landsat 5 TM with spatial resolution 30 m) at a scale of 1:200,000 over a territory of 52,000 km(2) and maps of human TBE case distribution (1971-2000) has been prepared using remote sensing and geographical information systems technologies. The influence of climate changes on a forest ecosystem inhabited by I. ricinus has been studied in the southern region of the Czech Republic. The analysis of long-term series (1931-2000) of climatologic and phenological characteristics has been carried out. The results are compared with the long-term series of TBE incidence. The influence of weather condition on day-to-day changes of I. ricinus host-seeking activities was studied in 2001-2004. Field observations were realized in the south-eastern periphery of Prague where the experimental plots for tick monitoring were established in a relevant type of forest growth (Querceto-carpinetum). I. ricinus activities were investigated by the flagging method on three plots (200 m(2) each) in weekly intervals (March to November) during 2001-2004. The instruments for micrometeorological observations were installed between the experimental plots. Macrometeorological data were used from the nearby Czech Hydrometeorological Institute first class meteorological observatory. Simple and multiple linear regression and quadratic regression were used to test the relation between weather modification and I. ricinus host-seeking activity. Two preliminary most suitable 'models' are demonstrated.

After higher rates of occupational or leisure diseases recorded in the Czech Republic in the second half of the last century it was found that the last climatic changes and catastrophic floods of 1997 and 2002 were followed by outbreaks of leptospirosis as the only re-emerging postflood infection. While in tropics and subtropics the monsoon season is typically followed by highly increased rates of leptospirosis in humans, even, with fatal outcomes, this phenomenon remained unknown under the climatic conditions of the Czech Republic where human leptospirosis has been reported rather sporadically, mostly in natural foci of infection, and its incidence rate is usually about 0.3% per 100,000 population. Nevertheless, after the unexpected vast floods of 1997 and 2002 that also afflicted natural foci of leptospirosis, the rates of reported and serologically confirmed cases of leptospirosis in the Czech Republic were three times as high as usual with the specific morbidity reaching 0.9 case per 100,000 population. In 1997, as many as 7156 persons were tested for leptospirosis in the Czech Republic: the disease was diagnosed and reported in 94 patients and in 2002, 92 out of 4999 persons tested were diagnosed with leptospirosis. Two thirds of these cases were from inundation areas, half of them being directly associated with floods (exposure to residual water, flood mud in cellars, etc.). Four case of Weil disease reported in 1997 were fatal. As many as 41 deaths from Weil disease have been reported in the Czech Republic since 1963 when the disease became reportable.

Repeated serological investigations (CFT, IFT, ELISA) of 50,000 pregnant women revealed that 5.1/1000 pregnancies in the Karviná district, Czech Republic are threatened by toxoplasmosis. In 2.8/1000 pregnancies the infection was contracted shortly before pregnancy, one third of them ended by spontaneous abortion. In this group the birth of a congenitally infected infant is rare. Primary infections of women who are already pregnant (2.3/1000 of pregnancies) are much more serious. This number comprises 1.2/1000 pregnancies with a spontaneous abortion and 1.2/1000 pregnancies leading to the delivery of a congenitally infected infant. By early detection, i.e. repeated serological examinations in all pregnancies, and by treatment of patients with Toxoplasma infections this hazard can be reduced substantially, i.e. to one eighth.