Dr. Murai Éva szerk.: Parasitologia Hungarica 24. (Budapest, 1991)

the patient considered borrelia infection as a real possibility, when the questionnaire was filled in.) The risk of neuroborreliosis was 2.42 times higher in cases of multiple tick bites (Table 4). Seasonality The total number of Lb cases and the number of seropositive patients are shown in Figure 14, in monthly distribution, according to the first clinical symptom. Taking into consideration that much more patients' material was sent to our lab for serological testing in the summer months, a better picture can be drawn if Lb cases are represented in the proportion of the patients tested (Fig. 15). An accumulation became visible in the early spring and late autumn. ECM showed a midsummer seasonality while ACA had no seasonality at all. The analysis of the few LBC cases suggests a more balanced seasonal distribution than that found for ECM. Dividing the rheumatological manifestations into arthralgia and frank arthritis seems to be justified by differences in the seasonal distribution of the two forms (Fig. 16). Neuroborreliosis has a seasonal pattern too. It is most pronounced in the CNS manifestations in the midsummer months, while in the case of peripheral neuritis an autumnal peak can be seen. Facial palsy has a relatively balanced distribution. Because of the screening characteristic of the latter symptom, it is worth to show the seropositive cases as a percentage of all cases examined (Fig. 17). A weak accumulation of the seropositive cases in the early spring and a stronger one in the autumn can be seen. The seasonal pattern can be better understood by showing the incubation time from the tick bite to the onset of different symptoms. It is the shortest in ECM: from a few days to 4 months (median: 10 days). The longest incubation time (1-3 years) was found in ACA. In most of the neurological manifestations an incubation time of 10-50 days (median: 32 days) was measured. Most of the frank arthritis developed from two months to two years, but 15% of them appeared in one month after the tick bite (Fig. 18). Arthralgia may develop at the onset of infection or several months later. Similar data can be derived by analysing the time that elapsed from the onset of ECM to the appearance of complications (Fig. 19). Neurological symptoms usually appear within a short time. Three peaks can be seen in the arthritis cases: an early form, almost at the time of development of ECM, the second with an incubation time of 3-8 months, and a late form appearing after 3 years. Arthralgia may develop at any time during the long disease process. Age The average age of the total examined population was 33.3 years, and that of the Lb cases was 34.3 years. The youngest seropositive was a 14-month-old patient suffering from ECM and facial palsy, the oldest an 83-year-old man with arthritis. Figure 20 shows that most of the patients examined were in the 10 to 15-year-old age group and in young adulthood. In contrast, the ratio of Lb cases in the examined population was highest in the youngest and in the oldest age groups. The high