Epidemiology of borrelia infections in Austria.

From April 1984 to July 1985 873 cases of Borrelia infections were registered at the Hygiene Institute of the University of Vienna. 2609 serum samples of these patients were investigated for antibodies against B. burgdorferi by means of IFA- and ELISA-tests. Erythema chronicum migrans (ECM) was recognized in 60.9% of patients, neurological abnormalities were recorded in 23.4% of which the majority manifested themselves as polyradiculitis and meningopolyneuritis (MPN). Acrodermatitis chronica atrophicans (ACA) was recognized in 11.5%. A small number of patients suffered from Lymphadenosis cutis benigna (LCB), arthritis and cardiac abnormalities. Sixty percent of patients were females and 40% males. Infections were found in all age groups ranging from 2-83 years in females and 1-85 years in males. Tick- or insect-bites prior to the onset of illness were reported by 47.2% and 15.6% of patients, respectively. The main vector is the hard tick Ixodes ricinus. Flying insects from the family tabanidae, i.e. Chrysops caecutiens and Haematopota species, must also be considered as transmitters. Antibodies to B. burgdorferi were found in 22.3%, 93.6% and 100% of sera from patients with ECM, MPN and ACA, respectively. Six of 11 patients with LCB and all with arthritis and cardiac abnormalities showed serologic reactivity. Geographically, Borrelia infections are distributed in all states of Austria. The seasonal distribution of cases show a peak in July and August, but the onset of clinical manifestation could be observed throughout the year. These results present Austria as an area where tick- or insect-borne Borrelia infections are very frequent and endemic in all Austrian states.