Long-term trends in the epidemiology of human leptospirosis (Slovak Republic, 1954-2006)

The purpose of this study was the observation of eventual shifts in some basic epidemiological features of human leptospirosis in Slovakia over a long period of time. Epidemiological traits of human leptospirosis were evaluated in three decades: 1954-1963 (822 cases), 1976-1985 (477 cases) and 1997-2006 (310 cases). The evaluation encompassed the aetiologic structure of cases, the incidence rate of diseases, men-to-women ratio of patients, as well as the professional and seasonal distribution of patients. The most affected feature was the incidence rate, which decreased by more than 70% over time. Another considerable change was the proportion of different major serological types of leptospirosis. The initially prevailing Sejroe infections fell to 4th place in the percentage rank, while Grippotyphosa disease, which was ranked 2nd place at the beginning of the observations, became dominating. Icterohaemorrhagiae disease climbed from 4th place to 2nd place. Third place was reserved by the Pomona + Tarassovi infections during the whole study period. A distinct tendency of age- and gender-specific incidence rate compared to the proportion of leptospirosis by age and gender was noticed; only minor alterations of the values of both parameters were registered over time. The overall value of the men-to-women ratio (MWR) of diseased persons was virtually within the same range in all three time periods but varied according to different age groups. The MWRs relative to the causal Leptospira serovars were stable over time but markedly differed among distinct serovars. Incidence rates related to age and aetiology showed different trends for the major serological types of leptospirosis. Changes were observed in the professional distribution of leptospirosis: there was an important proportional decrease of cases among farmers and field workers, an increase among house-wives + pensioners, but only some slight changes in abattoir workers/butchers, pupils + students and workers. The seasonal distribution of patients did not show any remarkable changes; the maximum percentage of cases occurred during the period extending from July to November during the whole period of observation. The epidemiological features of human leptospirosis underwent important shifts in the Slovak Republic over a 50-year period of time. They were very closely related to economical, social and political changes, which are discussed in this paper. The results may be useful for specialists in other European countries.