https://orcid.org/0000-0002-3095-0184
We report a case-series of two co-travellers from Florida, USA, who returned to the USA in June 2018 after an 11-day trip to Ireland (Figure 1a). The patients (Patient A adult male and Patient B adult female) found partially engorged ticks on the 6th and 10th day of travel, respectively (Figure 1b and c), which they removed with tweezers and stored in alcohol in a pill bottle. The exact location of where the ticks were encountered was not known. The patients did not camp or hike extensively during their trip. They did wear long pants during most of their outings, but did not use tick repellent during their outdoor activities. Upon return home, they sought care from their primary physician for potential Lyme Borrelia exposure, and both were treated prophylactically with 100 mg doxycycline BID for 3 weeks. Neither patient experienced any subsequent signs or symptoms. The ticks were later submitted to the investigative laboratory at the University of North Florida for species identification and Borrelia testing.
(a) Map of Ireland showing locations visited by two travellers from the USA in 2018; (b) the tick attached to patient A; (c) the tick attached to patient B
Both ticks were identified as Ixodes ricinus nymphs. Molecular sequencing of 12SrRNA, 16SrRNA and Cox1 DNA (Genbank OM779137, OM757843 and OM757845) of the tick from Patient A confirmed the species as I. ricinus and ruled out locally acquired Ixodes scapularis. Based on level of engorgement, the tick from Patient A was attached only ~24–48 hours, while the tick from Patient B was likely attached for at least 4 days (see Figure). Initial PCR screening for Borrelia species was positive for the tick from Patient A (Figure 1b) and the DNA sequence suggested a species within the Borrelia burgdorferi sensu lato complex. Subsequently, multi-locus sequence typing1 of 10 gene fragments, including 16S–23S rRNA intergenic spacer, clpA, clpX, nifS, ospC, pepX, pyrG, recG, rplB and uvrA (Genbank OM779140, OM780102–OM780105 and OM816715–OM816719) confirmed unequivocally the presence of Borrelia afzelii.
In Ireland, like much of Europe, I. ricinus is the primary vector of B. burgdorferi sensu lato genospecies that cause Lyme borreliosis in humans.2 Also known as the castor bean tick, I. ricinus parasitizes reptiles, birds, and small, medium, and large mammals. The ticks actively seek hosts by positioning themselves on the edges of low-lying vegetation to optimize chances of contact with a host that passes by.2
A 1996 survey of Borrelia species in I. ricinus in Ireland identified B. afzelii, along with B. burgdorferi sensu stricto and Borrelia garinii.3 A survey of I. ricinus in Ireland in 2018 demonstrated several pathogenic Borrelia species including Borrelia miyamotoi, B. garinii and Borrelia valaisiana, but failed to confirm B. afzelii in any samples.4 A more recent update5 found B. burgdorferi sensu lato in 9.2% of I. ricinus tested from sites throughout Ireland. A subset of analysed ticks showed that B. afzelii represented 2.4% of positive ticks.
Lyme borreliosis often presents with non-specific signs and symptoms such as fever, chills, malaise, fatigue and muscle or joint pain, and ~89% of infections present with erythema migrans skin rash.6 Infections with B. afzelii are more often associated with degenerative skin lesions.2 The human incidence of Lyme borreliosis in Ireland is around 0.2–2.0 cases per 100 000 population and varies by region,7 while the incidence in the USA is around 10 per 100 000.8 The present report demonstrates that travellers to Ireland, as to other areas of Europe, need to be aware of the presence of Borrelia infected human biting I. ricinus, and to take appropriate tick bite prevention measures. We further recommend that the CDC Travellers’ Health website mention Lyme disease as a risk for visitors to Ireland.
Author Statements
All authors have seen, approved and accept full responsibility for the content, and have full access to the data and analyses, as well as drafting and editing the manuscript.
Authors’ Contributions
B. Peterson drafted the manuscript and created the Figure/Images. K. Clark identified the ticks, conducted PCR testing and DNA sequence analysis, and edited the paper.
Acknowledgment
The authors thank S.H. and R.T. for providing the tick specimens and details about their experience following the tick bites.
Funding
This work was supported by donations from the Florida Lyme Disease Association and other private donors to K. Clark’s UNF Foundation Research Account.
Conflict of interest
The authors have declared no conflicts of interest.
