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Hauri A.M.,Hesse State Health Office | Hofstetter I.,Public Health Authority Darmstadt Dieburg | Seibold E.,National Reference Laboratory for Tularemia | Kaysser P.,National Reference Laboratory for Tularemia | And 4 more authors.
Emerging Infectious Diseases | Year: 2010

In November 2005, an outbreak of tularemia occurred among 39 participants in a hare hunt in Hesse, Germany. Previously reported tularemia outbreaks in Germany dated back to the 1950s. We conducted a retrospective cohort study among participants and investigated the environment to identify risk factors for infection. Ten participants had serologic evidence of acute Francisella tularensis infection; 1 other participant died before laboratory confirmation was obtained. Presence within 5 meters of the place where disemboweled hares were rinsed with a water hose was the risk factor most strongly associated with infection (risk ratio 22.1; 95% confidence interval 13.2-154.3). Swabs taken at the game chamber and water samples were PCR negative for F. tularensis. Eleven of 14 hare parts showed low-level concentrations of F. tularensis, compatible with cross-contamination. More than half of case-patients may have acquired infection through inhalation of aerosolized droplets containing F. tularensis generated during rinsing of infected hares.

Genchi M.,National Reference Laboratory for Tularemia | Prati P.,National Reference Laboratory for Tularemia | Vicari N.,National Reference Laboratory for Tularemia | Manfredini A.,National Reference Laboratory for Tularemia | And 5 more authors.
PLoS ONE | Year: 2015

Background: Tularemia is a zoonosis caused by the Francisella tularensis, a highly infectious Gramnegative coccobacillus. Due to easy dissemination, multiple routes of infection, high environmental contamination and morbidity and mortality rates, Francisella is considered a potential bioterrorism threat and classified as a category A select agent by the CDC. Tick bites are among the most prevalent modes of transmission, and ticks have been indicated as a possible reservoir, although their reservoir competence has yet to be defined. Tickborne transmission of F. tularensis was recognized in 1923, and transstadial transmission has been demonstrated in several tick species. Studies on transovarial transmission, however, have reported conflicting results. Objective: The aim of this study was to evaluate the role of ticks as reservoirs for Francisella, assessing the transovarial transmission of F. tularensis subsp. holarctica in ticks, using experimentally-infected females of Dermacentor reticulatus and Ixodes ricinus. Results: Transmission electron microscopy and fluorescence in situ hybridization showed F. tularensis within oocytes. However, cultures and bioassays of eggs and larvae were negative; in addition, microscopy techniques revealed bacterial degeneration/death in the oocytes. Conclusions: These results suggest that bacterial death might occur in oocytes, preventing the transovarial transmission of Francisella. We can speculate that Francisella does not have a defined reservoir, but that rather various biological niches (e.g. ticks, rodents), that allow the bacterium to persist in the environment. Our results, suggesting that ticks are not competent for the bacterium vertical transmission, are congruent with this view. Copyright © 2015 Genchi et al.

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