Prevalence of Borrelia burgdorferi in Ixodes ricinus Ticks in Urban Recreational Areas of Helsinki

Abstract

Lyme borreliosis, an infection caused by the tick-borne spirocheteBorrelia burgdorferi, is a major health problem for populations in areas of endemicity in the Northern Hemisphere. In the present study we assessed the density of ticks and the prevalence ofB. burgdorferi sensu lato among ticks in popular urban recreational areas of Helsinki, Finland. Altogether 1,688 Ixodes ricinus ticks were collected from five areas located within 5 km of the downtown section of Helsinki, and 726 of them (303 nymphs, 189 females, and 234 males) were randomly chosen for laboratory analysis. The midguts of the ticks were divided into three pieces, one for dark-field microscopy, one for cultivation in BSK-II medium, and one for PCR analysis. Ticks were found in all the study areas; their densities varied from 1 to 36 per 100 m along which a cloth was dragged. The rate of tick infection with B. burgdorferi sensu lato varied from 19 to 55%, with the average being 32%. Borellia afzelii was the most predominant genospecies in all the areas, and no B. burgdorferi sensu stricto isolates were detected. Only two ticks were concurrently infected with both B. afzelii and Borrelia garinii. Dark-field microscopy gave more positive results for B. burgdorferi than did cultivation or PCR analysis. However, the agreement between all three methods was fairly good. We conclude that Lyme borreliosis can be contracted even in urban environments not populated with large mammals like deer or elk. The disease should be taken into account in the differential diagnosis of certain symptoms of patients from these areas, and the use of measures to improve the awareness of the general population and health care officials of the risk of contracting the disease is warranted.

Prevalence of granulocytic Ehrlichia and Borrelia burgdorferi sensu lato in Ixodes ricinus ticks collected from Southwestern Finland and from Vormsi Island in Estonia

“…infection in the ticks of Turku and the Turku archipelago was 5% (range 0-11.6%). Earlier, Junttila et al have reported an average infection rate of 32% (range 19-55%) in ticks collected from Helsinki city parks (23). One reason for these discrepant findings may be that the method repertoire used by Junttila et al was more extensive than ours.…”

“…occur in Europe (19)(20)(21). In Finland, Borrelia garinii and Borrelia afzelii have been found to be the most prevalent genospecies (22,23).…”

Early dissemination of Borrelia burgdorferi without generalized symptoms in patients with erythema migransNote

“…In 15 patients, the genospecies was B. garinii, in 6 patients B. afzelii, and in one patient both genospecies were found. This was an inverse genospecies distribution of B. garinii and B.afzelii as compared to that reported for Finnish tick isolates by Junttila et al (17). They studied 726 ticks collected from urban parks in Helsinki and found B. afzelii in 99 ticks and B. garinii in 36 ticks.…”

“…One explanation for the high incidence may be the rural nature of the survey area. However, evidence is accumulating that ticks can be abundant and their rates of infestation with B. burgdorferi high even in highly urban environments (17). In Finland, about 1-2 million people live in areas where Lyme borreliosis is as endemic as in the survey area.…”

Transcriptional response of human dendritic cells toBorrelia garinii—defective CD38 and CCR7 expression detected

“…Bg Å218, a Finnish tick isolate, has been described previously elsewhere [29]. The bacteria were grown in liquid Barbour-Stoenner-Kelly II medium and passaged weekly.…”