Prevalence and Diversity ofBorreliaSpecies in Ticks That Have Bitten Humans in Sweden

Abstract

Members of the genus Borrelia are among the most common infectious agents causing tick-borne disease in humans worldwide. Here, we developed a Light Upon eXtension (LUX) real-time PCR assay that can detect and quantify Borrelia species in ticks that have fed on humans, and we applied the assay to 399 such ticks. Borrelia PCR-positive ticks were identified to species level by sequencing the products of conventional PCR performed using Borrelia group-specific primers. There was a 19% prevalence of Borrelia spp. in the detached ticks, and the number of spirochetes per Borrelia PCR-positive tick ranged from 2.0 ؋ 10 2 to 4.9 ؋ 10 5 , with a median of 7.8 ؋ 10 3 spirochetes. Adult ticks had a significantly larger number of spirochetes, with a median of 8.4 ؋ 10 4 compared to the median of nymphs of 4.4 ؋ 10 4 . Adult ticks also exhibited a higher prevalence of Borrelia (33%) than nymphs (14%). Among the identified species, Borrelia afzelii was found to predominate (61%) and was followed by B. garinii (23%), B. valaisiana (13%), B. burgdorferi sensu stricto (1%), B. lusitaniae (1%), and B. miyamotoi-like (1%). Also, 3% of the ticks were coinfected with multiple strains of B. afzelii. Notably, this is the first report of B. lusitaniae being detected in ticks in Sweden. Our LUX real-time PCR assay proved to be more sensitive than a corresponding TaqMan assay. In conclusion, the novel LUX real-time PCR method is a rapid and sensitive tool for detection and quantification of Borrelia spp. in ticks.Lyme borreliosis (LB) is the most common tick-borne disease in humans in Europe (26), and it is caused by spirochetes belonging to the Borrelia burgdorferi sensu lato complex. That group comprises the species B. burgdorferi sensu stricto, B. afzelii, and B. garinii, which are usually transmitted by the vector Ixodes ricinus. Furthermore, there have been reports of B. valaisiana, B. lusitaniae, and B. spielmanii being detected in samples of human skin and cerebrospinal fluid (5, 7, 30), which suggests that those three species can also give rise to LB. It is often hard to distinguish the clinical symptoms of LB from those of other diseases (10), and hence, it can be difficult to establish a correct diagnosis, especially if the patient is unable to recall having a tick bite.Today, diagnosis is based mainly on serological tests, although some PCR-based approaches, such as the TaqMan real-time PCR assay (3, 12), have been developed to detect Borrelia species in clinical samples. Even if real-time PCR is not yet considered to be a routine method in clinical practice, it can nonetheless provide valuable information about Borrelia infections, with regard to species type and the number of spirochetes present. Additional major advantages of PCR in this context are its simplicity, sensitivity, robustness, and speed.Other assays besides the TaqMan assay include a method based on SYBR green dye chemistry (37) and another using Light Upon eXtension (LUX) (Invitrogen Corporation). Compared to the SYBR green real-time PCR assay, the LUX assay o...

Tick-borne encephalitis virus in ticks detached from humans and follow-up of serological and clinical response

“…In order to assure the reproducibility of the RNA extraction and cDNA synthesis, and to prevent false-negative results, at least 2 randomly selected tick-samples in each 46-tick extraction batch were analyzed for the 16s rRNA gene of the Ixodes ricinus tick, with a realtime PCR assay (Wilhelmsson et al, 2010), using the forward primer F-16sIxodes and the reverse primer R-16sIxodes (Table 1).…”

Borrelia miyamotoi: egy újabb, humán patogén, kullancs által terjesztett, visszatérő lázat okozó baktérium

“…A B. miyamotoi nagy területen elterjedt, jelenleg 18 európai országból van adat az előfordulásáról (1. táblá-zat) [8,9,[13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. A növényzetről gyűjtött közönséges kullancsokban a fertőzöttek aránya 0,18% és 4,8% közöt-ti.…”

Study of a Cohort of 1,886 Persons To Determine Changes in Antibody Reactivity to Borrelia burgdorferi 3 Months after a Tick Bite

“…Serological samples and data collected from 1,886 persons in the TBD STING study bitten by one or more ticks from 2007 to 2009 were analyzed (2)(3)(4)(5). A total of 394 of these participants were also described previously (3).…”

“…Both the vector and the bacterium are prevalent in southern Scandinavia, and ticks frequently attach to humans and occasionally transmit B. burgdorferi (1)(2)(3)(4). Lyme borreliosis (LB) is also common in parts of the United States.…”

“…Ticks that had bitten humans in the Åland Islands, Finland, and different parts of Sweden were collected and analyzed at Linköping University (2)(3)(4)(5). The focus of this study was to analyze the differences in the measurements of B. burgdorferi-specific antibodies in the paired samples and propose methods for detecting changes in antibody reactivity.…”