Tick-borne Encephalitis and Possible Borrelial Serology
Tick-borne Encephalitis and Possible Borrelial Serology
In Europe, tick-borne encephalitis (TBE) virus causing TBE is transmitted by the bite of
 Ixodes ricinus tick, which can also transmit Lyme borreliae , the causative agent of Lyme
 borreliosis (LB). Since TBE and LB are both endemic with high incidence rates in Slovenia, we
 should be attentive to the possibility of double infections. Double infections with TBE virus
 and Lyme borreliae were reported to occur rarely even in endemic countries, however reliable
 data on coinfection rates are rather limited. Microbiological diagnosis of TBE virus
 infection is quite straightforward, and there is no specific therapy for TBE available so
 far. This markedly differs from borrelial infection, in which case interpretation of
 serological test results demands more caution, but there is highly efficient antibiotic
 treatment available for LB. This may lead to over prescribing of antibiotics to TBE patients
 with documented borrelial antibodies in serum indicating possible coinfection with Lyme
 borreliae, but missing clinical or microbiological criteria for proven borrelial coinfection.
 Approximately 10% of patients who had been treated appropriately for LB and about one third
 of patients after TBE report nonspecific subjective complaints, such as fatigue, headache,
 arthralgia, and myalgia, termed post-Lyme and post-encephalitic symptoms, respectively. These
 may not be differentiated clearly from nonspecific symptoms occurring with a rather
 substantial incidence also in the general population. A trend of ascribing medically
 unexplained nonspecific subjective symptoms to LB in subjects with positive borrelial
 antibodies in serum puzzles the situation further.

 The aim of this prospective observational study was to assess the proportion and clinical
 implication of proven and possible coinfection with Lyme borreliae in patients with TBE, and
 to evaluate the association between anti-borrelial antibiotic therapy and clinical outcome in
 the subgroup of patients with possible coinfection.
Inclusion Criteria:

 -  age ≥18 years

 -  admitted between January 2007 and December 2013 at the University Medical Centre
 Ljubljana, Slovenia

 -  tick-borne encephalitis defined according to European criteria (febrile illness with
 symptoms and/or signs of meningitis or meningoencephalitis, cerebrospinal fluid (CSF)
 pleocytosis (>5 × 106 cells/L), and demonstration of acute TBE virus infection (the
 presence of specific tick-borne encephalitis virus IgM and IgG antibodies in serum or
 demonstration of intrathecal production of specific TBE virus IgM and/or IgG
 antibodies in patients previously vaccinated against tick-borne encephalitis)

 Exclusion Criteria:

 -  Lyme borreliosis in the past