Immunofluorescence analysis reveals no increased seroprevalence of anti-Bartonella schoenbuchensis-IgG antibodies in German forest workers.

BACKGROUND: Bartonella schoenbuchensis is suspected to cause deer ked dermatitis and febrile diseases in humans. Deer keds (Lipoptena cervi), which infest cervids (e.g., roe deer, fallow deer), are discussed as potential vectors for B. schoenbuchensis. METHODS: We analyzed the seroprevalence of anti-B. schoenbuchensis immunoglobulin G (IgG) antibodies in sera of forest workers (FW; n = 82) compared to control sera of non-forest workers (NFW; n = 118) from North Rhine-Westphalia, Germany. For this purpose, an immunofluorescence assay (IFA) using Vero E6 cells infected with B. schoenbuchensis was established, and serum titers were assessed. Whole cell lysate of B. schoenbuchensis was introduced for analysis of seroreactivity by western blotting. Immunodominant proteins were identified by liquid chromatography-tandem mass spectrometry. RESULTS: When using human sera, 54.9% (n = 45/82) of FW were tested positive at a titre ≥ 320 whereas IFA reactivity was 66.1% (n = 78/118) in NFW. When the cut-off titre was set to ≥ 640, then 18,3% (n = 15/82) of FW and 20,3% (n = 24/118) of NFW displayed seroreactivity, respectively. In immunoblot analysis, IFA-positive sera reacted with 18 different bands ranging from ca. 40-300 kDa. No elevated reactivity of sera from FW compared to those of NFW was observed. CONCLUSIONS: Our data speak against an increased seroprevalence of anti-B. schoenbuchensis IgG titers in FW, which are regularly exposed to deer keds, weakening the hypothesis that B. schoenbuchensis is transmitted to humans by deer keds.