Fever, headache and meningism associated with signs of inflammation in serum (leukocytosis, elevation of the sedimentation rate and of C-reactive protein), and predominance of neutrophilic cells over lymphocytes in the CSF are main findings in patients with TBE, but are also highly indicative of bacterial meningitis. Consequently, most patients are treated with antibiotics – at least until the TBE serology is found to be positive.
Thus, many viral and bacterial infections have to be considered in the differential diagnosis of TBE.
Lyme disease (lyme borreliosis) has been recognized as the most frequent vector borne disease in mild climate areas, and has to be included in the differential diagnosis of TBE. Its causative agent, Borrelia burgdorferi sensu lato complex (B. burgdorferi sensu stricto, B. garinii and B. afzelii), is transmitted by ticks and other arthropods. In our part of the world, its incidence is higher than that of TBE. Contrary to TBE, the various stages and the manifestations of lyme borreliosis occur facultatively; transitions may be indistinct. High-dose administration of penicillin, cephalosporin, macrolide or doxycycline is the therapy of choice.
Acute human granulocytic ehrlichiosis (HGE) is an emerging tick-borne disease, which should now be included in the differential diagnosis of febrile illnesses occurring after a tick bite in Europe. HGE is caused by Ehrlichia phagocytophila (Anaplasma), gramnegative intracellular bacteria infecting white blood cells. Comparing the clinical signs and laboratory findings of adult patients with proven acute HGE with that of patients in the initial phase of tick-borne encephalitis shows that the duration of fever in the initial phase of TBE is shorter (median 4 days vs. 7 days in patients with acute HGE). Clinical signs including chills, myalgia and arthralgia, and laboratory findings e.g. elevated values for lactate dehydrogenase and C-reactive protein direct towards a diagnosis of acute HGE rather than the initial phase of TBE.