Estimation of the transmission probability of Lyme Borreliosis

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Whether physicians should prophylactically treat tick bites in areas endemic for Lyme disease has been debated. The high rates of tick infection (10-50%) found in Lyme disease-endemic areas suggest that tick bites should be treated; conversely, the low rates of Lyme disease (1-4%) found in recent clinical trials of untreated tick-bite victims suggest caution in treatment. Medical advice given from Lyme-disease World Wide Web sites is equally contradictory, ranging from suggesting that all tick bites should be treated to suggesting that no tick bites be treated. To clarify this issue, we estimate the transmission probability of the causative agent of Lyme disease, Borrelia burgdorferi, for different durations of tick attachment. The data used to estimate this transmission probability is obtained from previously published animal studies. The accuracy of these estimates is assessed by comparing model predictions of the number of Lyme disease cases to that actually observed in clinical studies of Lyme disease. Our results suggest that tick bites should be treated only when it is known that the duration of tick attachment is longer than 48 hours.

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Biometrical Journal