Lyme Borreliosis in Finland, 1995-2014.

We investigated the epidemiology of Lyme borreliosis (LB) in Finland for the period 1995-2014 by using data from 3 different healthcare registers. We reviewed data on disseminated LB cases from the National Infectious Diseases Register (21,051 cases) and the National Hospital Discharge Register (10,402 cases) and data on primary LB (erythema migrans) cases from the Register for Primary Health Care Visits (11,793 cases). Incidence of microbiologically confirmed disseminated LB cases increased from 7/100,000 population in 1995 to 31/100,000 in 2014. Incidence of primary LB cases increased from 44/100,000 in 2011 to 61/100,000 in 2014. Overall, cases occurred predominantly in women, and we observed a bimodal age distribution in all 3 registers. Our results clearly demonstrate that the geographic distribution of LB has expanded in Finland and underscore the importance of LB as an increasing public health concern in Finland and in northern Europe in general.

Lyme Borreliosis and Deficient Mannose-Binding Lectin Pathway of Complement.

Risk factors for the widely endemic and much-debated tick-borne infection, Lyme borreliosis (LB), are unknown. The mannose-binding lectin (MBL) pathway of the complement cascade has an essential role in the eradication of Borrelia burgdorferi. A sufficient concentration of biologically active MBL in body fluids is an indicator of proper function of the MBL pathway. In this study, we investigated whether impaired MBL pathway function, represented by reduced serum MBL concentration, predisposes individuals to LB. First, we determined a serum MBL concentration cut-off level associated with diminished MBL pathway function in a group of 201 individuals. Then, we identified 350 borrelia Ab+ LB patient serum samples and 350 Ab- control samples from the archives of our laboratory and measured serum MBL concentrations in both sample groups. The concentration data were analyzed statistically using logistic regression, controlling for MBL cut-off, age, gender, and age and gender interaction. Serum MBL concentrations < 787 and < 445 ng/ml were associated with diminished and deficient MBL pathway function, respectively. Using these cut-offs, diminished (41.4 versus 27.4%, p = 0.0027) and deficient (26.3 versus 17.1%, p = 0.0361) MBL pathway functions were observed statistically more frequently in the LB patient samples than in the control samples. Also, the age-adjusted median serum MBL concentrations were significantly lower in the LB patient samples than in the non-LB controls. Our findings indicate that a deficiency in the MBL pathway of the complement cascade is a risk factor for developing disseminated Ab+ LB.

Population-based Borrelia burgdorferi sensu lato seroprevalence and associated risk factors in Finland.

Lyme borreliosis (LB) is caused by Borrelia burgdorferi sensu lato (Bb-sl) and is the most common vector-borne disease in Europe. The objectives of this study were to determine the Bb-sl seroprevalence among the general Finnish adult population and to identify risk factors associated with Bb-sl-seropositive status. Two thousand sera from a nationwide health survey from 2011 were tested by whole-cell sonicate IgG ELISA, C6 peptide ELISA, and recomBead IgG 2.0 and test results were linked to a general health questionnaire. A multivariable logistic regression model was used to identify risk factors. The median age of the study population was 56 years (range 29-97) and the Bb-sl weighted seroprevalence was 3.9% (95% confidence interval (CI) 3.03-5.08). The weighted seroprevalence was significantly higher among males than females (adjusted odds ratio 1.91, 95%CI 1.21-3.04). The seroprevalence was highest in Southern, Central, and Eastern regions. The first Bb-sl seroprevalence study in Finland showed a seroprevalence of 3.9% (regional range 0.87%-6.12%). The results of this study can be used, together with previous data on LB incidence and spatial tick distribution, to target public health communication about preventive measures.

Crowdsourcing-based nationwide tick collection reveals the distribution of Ixodes ricinus and I. persulcatus and associated pathogens in Finland.

A national crowdsourcing-based tick collection campaign was organized in 2015 with the objective of producing novel data on tick distribution and tick-borne pathogens in Finland. Nearly 20 000 Ixodes ticks were collected. The collected material revealed the nationwide distribution of I. persulcatus for the first time and a shift northwards in the distribution of I. ricinus in Finland. A subset of 2038 tick samples containing both species was screened for Borrelia burgdorferi sensu lato (the prevalence was 14.2% for I. ricinus and 19.8% for I. persulcatus), B. miyamotoi (0.2% and 0.4%, respectively) and tick-borne encephalitis virus (TBEV; 0.2% and 3.0%, respectively). We also report new risk areas for TBEV in Finland and, for the first time, the presence of B. miyamotoi in ticks from mainland Finland. Most importantly, our study demonstrates the overwhelming power of citizen science in accomplishing a collection effort that would have been impossible with the scientific community alone.