Substantial exposure to Borrelia miyamotoi occurs through bites from Ixodes ricinus ticks in the Netherlands, which also transmit Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum. Direct evidence for B. miyamotoi infection in European populations is scarce. A flu-like illness with high fever, resembling human granulocytic anaplasmosis, has been attributed to B. miyamotoi infections in relatively small groups. Borrelia miyamotoi infections associated with chronic meningoencephalitis have also been described in case reports. Assuming that an IgG antibody response against B. miyamotoi antigens reflects (endured) infection, the seroprevalence in different risk groups was examined. Sera from nine out of ten confirmed B. miyamotoi infections from Russia were found to be positive with the recombinant antigen used, and no significant cross-reactivity was observed in secondary syphilis patients. The seroprevalence in blood donors was set at 2.0% (95% CI 0.4–5.7%). Elevated seroprevalences in individuals with serologically confirmed, 7.4% (2.0–17.9%), or unconfirmed, 8.6% (1.8–23%), Lyme neuroborreliosis were not significantly different from those in blood donors. The prevalence of anti-B. miyamotoi antibodies among forestry workers was 10% (5.3–16.8%) and in patients with serologically unconfirmed but suspected human granulocytic anaplasmosis was 14.6% (9.0–21.8%); these were significantly higher compared with the seroprevalence in blood donors. Our findings indicate that infections with B. miyamotoi occur in tick-exposed individuals in the Netherlands. In addition, B. miyamotoi infections should be considered in patients reporting tick bites and febrile illness with unresolved aetiology in the Netherlands, and other countries where I. ricinus ticks are endemic.
A one-year serological and clinical follow-up study was conducted to assess the prevalence and incidence of asymptomatic and symptomatic infection with Borrelia burgdorferi among 151 Dutch forestry workers. The prevalence of antibodies to Borrelia burgdorferi among the forestry workers and among office employees as control group was compared. Antibodies to Borrelia burgdorferi were detected by enzyme immunoassay. Forestry workers were examined physically at the start of the study. Clinical follow-up of forestry workers whose first blood sample was positive and of persons showing seroconversion was done by telephone interview. If Lyme borreliosis was suspected, clinical and laboratory data were obtained. The seroprevalence was significantly higher among forestry workers (28%) than among controls (5%). Of 127 forestry workers who were examined, 7 (18%) of the 39 seropositive persons but none of the seronegative persons had a history of Lyme borreliosis. None of 32 asymptomatic seropositive forestry workers had developed Lyme borreliosis one year later. The incidence of infection with Borrelia burgdorferi as demonstrated by seroconversion among 95 initially seronegative forestry workers was 5%. None of them had Lyme borreliosis. Infection with Borrelia burgdorferi among forestry workers is frequent but seems to take a benign course.
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