Candidatus Neoehrlichia mikurensis and Borrelia burgdorferi sensu lato detected in the blood of Norwegian patients with erythema migrans

The most common tick-borne human disease in Norway is Lyme borreliosis. Ticks in Norway also harbour less known disease-causing agents such as Candidatus Neoehrlichia mikurensis, Borrelia miyamotoi and Rickettsia heivetica. However, human infections caused by these pathogens have never been described in Norway. The main aims of the study were to evaluate the contribution of several tick-borne bacterial agents, other than Borrelia burgdorferi sensu lato, to zoonotic diseases in Norway and to determine their clinical pictures. Blood samples from 70 symptomatic tick-bitten adults from the Agder counties in southern Norway were screened for seven tick-borne pathogens by using a commercial multiplex PCR-based method and by singleplex real-time PCR protocols. Most patients (65/70) presented with a rash clinically diagnosed as erythema migrans (EM). The most frequently detected pathogen DNA was from Ca. N. mikurensis and was found in the blood of 10% (7/70) of the patients. The Ca. N. mikurensis-infected patients presented with an EM-like rash as the only symptom. B. burgdorferi s.l. DNA was present in the blood of 4% (3/70) of the study participants. None had detectable Anaplasma phagocytophilum, B. miyamotoi, Rickettsia typhus group or spotted fever group, Francisella tularensis, Coxiella burnetii or Battonella spp. DNA in the blood. The commercially available multiplex PCR bacteria flow chip system failed to identify half of the infected patients detected by corresponding real-time PCR protocols. The recovery of Ca. N. mikurensis DNA was higher in the pellet/plasma fraction of blood than from whole blood. To conclude, Co.. N. mikurensis appeared to be the etiological agent in patients with EM in a surprisingly large fraction of tick-bitten persons in the southern part of Norway.