Abstract
In Scandinavia, tick-borne infections affecting humans include Lyme borreliosis (LB), tick-borne encephalitis (TBE) and human granulocytic anaplasmosis (HGA). Each of these infections can present with unspecific symptoms. In this prospective clinical study, we recruited patients based on two independent inclusion criteria; 1) patients with unspecific symptoms, i.e. fever (≥38.0℃) or a history of feverishness and/or any combination of headache, myalgia or arthralgia and 2) patients with erythema migrans (EM), following an observed tick bite or tick exposure within one month prior to onset of symptoms. A total of 206 patients fulfilled the study. Among these, we could identify 186 cases of LB (174 with EM), 18 confirmed and two probable cases of HGA and two cases of TBE. Thirteen of the HGA cases presented without fever. Furthermore, 22 of the EM patients had a sub-clinical co-infection with Anaplasma phagocytophilum, based on serology. Both TBE cases had co-infections, one with Borrelia burgdorferi and one with Anaplasma phagocytophilum. We conclude that it is important to consider several causative agents and possible co-infections in the clinical management of infectious diseases where ticks may be suspected as vectors.
Highlights
Hard ticks, in Sweden mainly Ixodes ricinus, transmit several zoonotic agents, the most well-known being bacteria Borrelia burgdorferi sensu latu (B. burgdorferi), Anaplasma phagocytophilum (A. phagocytophilum) and tick-borne encephalitis (TBE) virus
This prospective clinical multi-centre study in the southeast part of Sweden was designed to estimate the extent to which tick-associated unspecific symptoms or fever could be attributed to B. burgdorferi, A. phagocytophilum, or TBE virus
Our study indicates that a patient with both erythema migrans (EM) and clinical symptoms can be interpreted as a clean-cut case of Lyme borreliosis, while it may constitute a true clinical case of HGA, mixed with EM due to a co-infection with Borrelia
Summary
In Sweden mainly Ixodes ricinus, transmit several zoonotic agents, the most well-known being bacteria Borrelia burgdorferi sensu latu (B. burgdorferi), Anaplasma phagocytophilum (A. phagocytophilum) and tick-borne encephalitis (TBE) virus. Each of these causative agents can initially induce fever and unspecific symptoms, including headache, myalgia and arthralgia [1]-[6]. Ixodes ricinus is distributed mainly in the south and central parts of Sweden, and along the east-coast up to Umeå This coincides with the distribution of borreliosis and anaplasmosis, while TBE cases are distributed in a patchier, geographically localised way [7]. We wanted to reveal co-infections with these agents in patients with localised Borrelia infection, i.e. erythema migrans (EM)
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