[Risk factors associated with the presence of antibodies against Borrelia burgdorferi]. / Factores de riesgo asociados con la presencia de anticuerpos contra Borrelia burgdorferi.

BACKGROUND: The seroprevalence of Borrelia burgdorferi infection in risk populations is not well known and varies from area to area due to its marked local trend. OBJECTIVE: To know the seroprevalence of B. burgdorferi infection in persons with high risk for acquiring the disease on account of their outdoor activities, as well as parameters determining that risk. PATIENTS AND METHODS: A cross-sectional study was undertaken with a sample size of 302 voluntary people corresponding to risk populations in the Biscay province by means of an epidemiologic questionnaire as well as serology (ELISA and immunoblot) against B. burgdorferi. RESULTS: A total of 106 individuals (35%) were positive, with no differences regarding sex. The predominant age interval was between 51 and 60 years. The groups with the highest risk for seropositivity were shepherds (42%) and apiculturists (41%). There was a positive correlation with the number of years spent on the activity. Sixty percent of the total studied population remembered a tick bite in the last five years; among seropositive patients, 64% of them remembered that event. There were no differences regarding the type or rural or urban house. However, differences were indeed marked regarding the geographic distribution where the activity took place, which is consistent with the focal distribution of the disease. CONCLUSIONS: Outdoor activities represent a considerable risk factor for acquiring B. burgdorferi infection and a high prevalence (35%) of seropositivity was observed among such groups in the Biscay province. Educational public health campaigns addressed to the different risk groups might help prevent this infection.