Hare-to-Human Transmission of Francisella tularensis subsp. holarctica, Germany

In November 2012, a group of 7 persons who participated in a hare hunt in North Rhine-Westphalia, Germany, acquired tularemia.Two F. tularensis subsp.holarctica isolates were cultivated from human and hare biopsy material.Both isolates belonged to the FTN002-00 genetic subclade (derived for single nucleotide polymorphisms B.10 and B.18), thus indicating likely hare-to-human transmission.T ularemia is a zoonotic disease caused by the gram-neg- ative bacterium Francisella tularensis (1).Currently, there are 4 validly published subspecies.F. tularensis subsp.tularensis is the most virulent subspecies and occurs only in North America.F. tularensis subsp.holarctica is less virulent and occurs throughout the Northern hemisphere.F. tularensis subsp.mediasiatica was isolated in central Asia, and F. tularensis subsp.novicida, which has low virulence in humans, seems to be distributed globally (2).Various PCR-based assays have been established for the detection of F. tularensis or for the diagnosis of tularemia.An accurate population structure has been defined by using single nucleotide polymorphisms (SNPs) and insertion/deletion mutations (INDELs) with potential canonical properties.Currently, this population is divided into 4 major genetic clades: B.4, B.6, B.12, and B.16 (3-6).The taxonomic nomenclature of major clades in F. tularensis subsp.holarctica is based on clade-specific canonical SNP markers (3,4).In Europe, the strains of clades B.12 and B.6 dominate (6).The latter is found particularly in large areas in northern, western, and central Europe, including Germany (5-9). The StudyOn November 2, 2012, 15 European brown hares (Lepus europaeus) were shot during a hunt in Rüthen-Meiste, district Soest in the federal state of North Rhine-Westphalia, Germany (Figure ).The animals seemed healthy and showed normal escape behavior.Upon inspection, the animals that had been shot showed no signs of disease.Consequently, all animals were skinned, eviscerated, and dissected.Portioning of the hares was done 2 days later.Within a few days, 7 healthy persons who had contact with the hare carcasses showed varied symptoms of illness.Tularemia was suspected because of the signs and symptoms in combination with exposure in a tularemiaendemic area.Exposure, clinical symptoms, and time of onset of symptoms of all patients (A to G) are described in the Table .All patients were treated successfully with doxycycline.Human serum samples were collected about 5 weeks after infection from patients C and E and pleural fluid was obtained from patient E. On day 2 of incubation, the human isolate (12T0062) showed small pale-white to gray colonies on Columbia blood agar and chocolate agar, whereas no growth occurred on MacConkey agar plates.Ten organ specimens (from aorta, back and thigh muscles, lymph nodes, spinal cord) from 4 of the hares handled by the patients were tested for Francisella spp. in the National Reference Laboratory for Tularemia at the Friedrich-Loeffler-Institut in Jena, Germany.From all hare organs, only a single Francisella sp. was isolated from a spinal cord sample (13T0009) on cysteine heart agar Becton Dickinson GmbH, Heidelberg, Germany), which contains antibiotics.The strains were susceptible to erythromycin with inhibition zones between 22 and 24 mm corresponding to biovar I. Details of further methods that have been applied in the study are shown in the online Technical Appendix (http://wwwnc.cdc.gov/EID/article/21/1/13-1837-Techapp1.pdf).Both samples were identified as F. tularensis subsp.holarctica of clade B.6.For B.19, the SNP was C; results of Ftind33 and Ftind38 assays were IN, and the result of the Ftind49 assay was DEL.Both samples had T for SNP B.7, G for B.10 and T for B.18.Therefore, the strains were considered derived from SNPs B.10 and B.18. Blood serum samples of patients C and E were positive for F. tularensis with very high values of the optical density in the ELISA, 2.886 and 3.121, respectively. Hare-to-Human Transmission of Francisella tularensis subsp. holarctica, Germany