Abstract
Tularemia is a zoonotic disease caused by Francisella tularensis a small, pleomorphic, facultative intracellular bacterium. In Europe, infections in animals and humans are caused mainly by Francisella tularensis subspecies holarctica. Humans can be exposed to the pathogen directly and indirectly through contact with sick animals, carcasses, mosquitoes and ticks, environmental sources such as contaminated water or soil, and food. So far, F. tularensis subsp. holarctica is the only Francisella species known to cause tularemia in Germany. On the basis of surveillance data, outbreak investigations, and literature, we review herein the epidemiological situation—noteworthy clinical cases next to genetic diversity of F. tularensis subsp. holarctica strains isolated from patients. In the last 15 years, the yearly number of notified cases of tularemia has increased steadily in Germany, suggesting that the disease is re-emerging. By sequencing F. tularensis subsp. holarctica genomes, knowledge has been added to recent findings, completing the picture of genotypic diversity and geographical segregation of Francisella clades in Germany. Here, we also shortly summarize the current knowledge about a new Francisella species (Francisella sp. strain W12-1067) that has been recently identified in Germany. This species is the second Francisella species discovered in Germany.
Highlights
Tularemia, called “rabbit fever”, is a rare but potentially severe zoonosis caused by Francisella tularensis
By sequencing 12 F. tularensis subsp. holarctica isolates recovered from clinical samples in 2019, we identified two additional subclades: B.12/B.80 and B.6/B90, which have not been previously isolated from patients in Germany [22]
Tularemia is a seasonal disease in Germany, with most patients (63%) reporting symptom onset from July through November (Figure 3) when reservoir animal populations are peaking and frequent outdoor activities facilitate contact between wildlife and humans
Summary
Called “rabbit fever”, is a rare but potentially severe zoonosis caused by Francisella tularensis. Isolate W12-1067) were identified [22,30] This isolate is the only Francisella species described as being present in Germany next to F. tularensis subsp. Included in the review are data of sequenced genomes of Francisella isolates from patients recovered in 2019, adding new findings about genetic diversity and the geographical segregation of clades in Germany. Holarctica in Germany, as in other European countries, seems to be still underestimated and further investigations are needed, as shown by recent data obtained in France (82 new B.6 subclades were described) [40]. Taking into account latest findings, Germany might be a “melting pot” for the species, a region where strains become mixed and new genetic variants arise [21,22,36,41,42]
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