Ticks are obligate haematophagous acarines that parasitise every class of vertebrate (including man) and have a worldwide distribution. An increasing awareness of tick-borne diseases among clinicians and scientific researchers has led to the recent description of a number of emerging tick-borne bacterial diseases. Since the identification of Borrelia burgdorferi as the agent of Lyme disease in 1982, 11 tick-borne human bacterial pathogens have been described in Europe. Aetiological diagnosis of tick-transmitted diseases is often difficult and relies on specialised laboratories using very specific tools. Interpretation of laboratory data is very important in order to establish the diagnosis. These guidelines aim to help clinicians and microbiologists in diagnosing infection transmitted by tick bites and to provide the scientific and medical community with a better understanding of these infectious diseases.

The pathogenic role of Rickettsia slovaca was first demonstrated in 1997 in a patient who presented with a single inoculation lesion of the scalp and enlarged cervical lymph nodes after receiving a bite from a Dermacentor tick. Subsequently, we evaluated the occurrence of R. slovaca infections among patients living in France and Hungary who presented with these symptoms. R. slovaca infections were confirmed by polymerase chain reaction (PCR) in 17 of 67 enrolled patients. Infections were most likely to occur in patients aged <10 years and in patients who were bitten during the colder months of the year. The median duration of incubation for the disease was 7 days. Fever was present in only 2 patients, and only 1 patient developed a rash. Sequelae included persistent asthenia (3 cases) and localized alopecia (4 cases). Immunofluorescence and/or Western blot analysis detected antibodies in 50% of tested patients. Three Dermacentor ticks obtained from patients revealed R. slovaca by PCR.

Our results indicate that an untreated maternal Borrelia burgdorferi s.l. infection may be associated with an adverse outcome, although bacterial invasion of the fetus cannot be proven. It appears that a specific syndrome representing 'congenital Lyme borreliosis' is unlikely.

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