Serological and molecular evidence of human granulocytic ehrlichiosis focus in the Białowieza Primeval Forest (Puszcza Białowieska), northeastern Poland.

Human granulocytic ehrlichiosis (HGE) is an emerging tickborne zoonosis. First described in the USA, it is being increasingly reported from several European countries. This study was undertaken to provide serological and molecular evidence of the occurrence of the HGE focus in the Białowieza Primeval Forest, located in northeastern Poland. To this end, the seroprevalence of HGE in this area, where Lyme borreliosis and tickborne encephalitis are highly endemic, was determined by means of an indirect immunofluorescence antibody assay. In addition, the frequency of granulocytic Ehrlichia spp. infection in Ixodes ricinus ticks from the same area was estimated using a polymerase chain reaction method with EHR 521 and EHR 747 primers, which amplified a fragment of 16S rDNA. The rate of seropositivity for HGE was 6.2% (8/130 subjects). Individuals seropositive for Lyme borreliosis were more likely to have anti-HGE antibodies than seronegative ones (P<0.05; OR=6.34, 95%CI=1.12-36.98). There was no association between self-reported frequency of tick bites or forestry employment and HGE seropositivity. Sixty of 376 (16%) Ixodes ricinus ticks tested were positive for the Ehrlichia phagocytophila genogroup by polymerase chain reaction. Ehrlichial DNA was present in 59 of 302 (19.5%) adult ticks and in 1 of 74 nymphs (1.4%). There was a significantly higher infection rate among female ticks (32.9%; 49/149) than among male ticks (6.5%; 10/153) (P<0.05). Dual infection with Ehrlichia spp. and Borrelia burgdorferi sensu lato was detected in 10 samples that were positive for ehrlichiae. The results obtained confirm the perpetuation of the HGE agent in the primeval forest ecosystem of northeastern Poland.