Low sero-prevalence of Lyme borreliosis in the forested mountainous area of Gorski Kotar, Croatia.

AIM Clinical forms of Lyme disease in Gorski Kotar have occurred only sporadically, in contrast to the northwestern Croatia and the neighboring areas of Slovenia, which are well-known Lyme borreliosis endemic regions. Our aim was to assess the level of sero-prevalence of Borrelia burgdorferi sensu lato in a high-risk population of forestry workers in the mountainous region of Gorski Kotar, Croatia, and compare it with the sero-prevalence in the residents of that area and the neighboring littoral region. METHODS A sero-epidemiological study was conducted on 520 healthy subjects, divided in 3 groups: the first group included 234 forestry workers, residents of Gorski Kotar, the second 100 residents of various professions in the same region, and the third 186 subjects of various professions from the neighboring littoral region. The sera were collected during the winters of two successive years, 1997 and 1998. Lyme borreliosis serology was performed by indirect immunofluorescence assay. Sera from 10 hunting dogs from Gorski Kotar were also analyzed. RESULTS The IgG antibodies to B. burgdorferi sensu lato were found in 11 examinees (4.7%) from the group of forestry workers, in 3 (3%) from the second group, and in 5 (2.7%) from the third group. Four out of 10 dogs (40%) had IgG antibodies against B. burgdorferi. CONCLUSION Our results show that the forest and mountainous area of Gorski Kotar, Croatia, has the characteristics of a low sero-prevalence area, in contrast to the endemic neighboring areas.