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To obtain detailed information about the current geographical distribution and incidence of tick bites and
Lyme borreliosis in the Netherlands and to identify regional differences in the ecological risk factors that might be involved.
Retrospective questionnaire study.
All Dutch general practitioner’s (GP) practices.
In April 2002, all GPs in the Netherlands were asked to complete a short questionnaire on the number of cases of tick bites and erythema migrans seen in 2001 and the size of their practice. Associations with possible risk factors were determined at the municipal level. Results were compared with the results of a similar study done in 1995.
The response of the GPs was 64.5% (4730/7330). Together, all GPs reported seeing approximately 61,000 patients in 2001 with tick bites and 12,000 patients with erythema migrans. The incidence of erythema migrans was estimated at 73 per 100,000 inhabitants. There were obvious risk areas. At the municipal level, tick bites and erythema migrans were positively associated with the area covered by forest, sandy soil, the number of roe deer and tourism. There was a negative association with the degree of urbanisation. Increases in tourism in areas with many ticks, new forests in urban regions and an increased number of horses were positively associated with the increase in tick bites and erythema migrans since 1994.
The number of patients with tick bites and erythema migrans seen by GPs in the Netherlands had doubled between 1994 and 2001. This increase may be attributed partly to changes in ecological risk factors and human behaviour. The number of cases of
Lyme borreliosis may be reduced by giving prophylactic information annually about ticks and ways to remove them, plus additional education of patients about the recognition of erythema migrans.