First Draft Genome Sequences of Three Strains of Francisella tularensis subsp. holarctica, Isolated from Hares and a Tick in France

ABSTRACT Here, we report the complete genome sequences of three strains of Francisella tularensis subsp. holarctica (11-789-5S, 11-935-13S, and 11-930-9S), isolated from brown hares and a tick during a tularemia outbreak in France, where tularemia is endemic.

T ularemia is a zoonosis caused by Francisella tularensis. This bacterium is a Gramnegative, coccoid rod, nonmotile, and non-spore-forming organism that is an obligate aerobe with optimal growth at 37°C. Tularemia occurs naturally in lagomorphs and in rodents. A wide range of other mammals and several species of birds have also been reported to be infected (1). Two types of F. tularensis are recognized on the basis of their epidemiology and virulence in hosts. Francisella tularensis subsp. tularensis (type A) is associated with lagomorphs in North America. Francisella tularensis subsp. holarctica (type B) occurs mainly in aquatic rodents in North America and in hares and small rodents in Eurasia. Type B is water or arthropod borne and is less virulent to humans and rabbits than type A (2). Tularemia is a notifiable zoonosis in France and is listed as a potential bioterrorist weapon (3). Tularemia is endemic in France and occurs usually as sporadic cases. In winter 2011, we reported an outbreak of tularemia in brown hares near Habarcq in Pas-de-Calais, France. This outbreak was the first one in the area and was characterized by a high mortality rate in the local hare population (4).
Here, we present the complete genome sequences of three F. tularensis subsp. holarctica strains, two of which were isolated during the Habarcq outbreak from a hare (11-935-13S) and from a questing tick that was caught (11-789-5S). The third strain, 11-930-9S, was isolated in the same period from a sporadic case in a brown hare found dead in another area. These isolates were confirmed to be F. tularensis by both bacteriological and real-time PCR (5). All procedures were performed under biosafety level 3 conditions. Further, subtyping of F. tularensis colonies was performed by PCR targeting of the genomic region RD1 that allows differentiation between F. tularensis subsp. tularensis and F. tularensis subsp. holarctica (6).
The sequencing data could be compared with those of strains isolated from human cases of tularemia to study the epidemiological link between human and animal cases.

ACKNOWLEDGMENTS
Financial support was provided by the National Hunting and Wildlife Agency (ONCFS).
We are grateful to the French departmental veterinary laboratories for providing samples and departmental hunting federations for their contribution to the wildlife surveillance.