Ulceroglandular form of tularemia after squirrel bite: a case report

Abstract

Background: The diagnosis of tularemia is not often considered in Germany as the disease is still rare in this country. Nonetheless, Francisella tularensis, the causative agent of tularemia, can infect numerous animal species and should, therefore, not be neglected as a dangerous pathogen. Tularemia can lead to massively swollen lymph nodes and might even be fatal without antibiotic treatment. To our knowledge, the case described here is the first report of the disease caused by a squirrel bite in Germany.

Case presentation: A 59-year-old German woman with a past medical history of hypothyroidism and cutaneous lupus erythematosus presented at the emergency room at St. Katharinen Hospital with ongoing symptoms and a swollen right elbow persisting despite antibiotic therapy with cefuroxime for 7 days after she had been bitten (right hand) by a wild squirrel (Eurasian red squirrel). After another 7 days of therapy with piperacillin/tazobactam, laboratory analysis using real-time polymerase chain reaction (PCR) confirmed the suspected diagnosis of tularemia on day 14. After starting the recommended antibiotic treatment with ciprofloxacin, the patient recovered rapidly.

Conclusion: This is the first report of a case of tularemia caused by a squirrel bite in Germany. A naturally infected squirrel has recently been reported in Switzerland for the first time. The number of human cases of tularemia has been increasing over the last years and, therefore, tularemia should be taken into consideration as a diagnosis, especially in a patient bitten by an animal who also presents with headache, increasing pain, lymphadenitis, and fever, as well as impaired wound healing. The pathogen can easily be identified by a specific real-time PCR assay of wound swabs and/or by antibody detection, for example by enzyme-linked immunosorbent assay (ELISA), if the incident dates back longer than 2 weeks.

Keywords: Case report; Eurasian red squirrel; Francisella tularensis subspecies holarctica; Tularemia; Zoonosis.

Fig. 1

Picture of the right hand of the patient at day 14 after the squirrel bite on the digit IV. After presentation of the ulcerous lesion and the local lymphadenitis of the right elbow in combination with the non-effective antibiotic treatment using three different antibiotics over 2 weeks, the suspicion of an ulcero-glandular tularemia was expressed

Fig. 2

Phylogenetic relationship of Francisella tularensis ssp. holarctica (Fth) in a wound swab sample from digit IV of the patient’s right hand (A-1825/1) (red, in bold) to Fth isolates from North Rhine-Westphalia (NW), Rhineland-Palatinate (RP), and Hesse (He). Strains belonging to the erythromycin-sensitive major clade B.6 are indicated in blue. For each genome sequence, the year of sampling, the host organism, sampling spot (German federal states), and the known final subclade are given. Host organisms: Be beaver, Br brock, H human, Le Lepus, Sc Sciurus, Wb wild boar. Germany’s federal states: BB Brandenburg, HE Hesse, NI Lower Saxony, NW North Rhine-Westphalia, RP Rhineland-Palatinate. Countries: D Germany, FR France. Asterisk indicates no bacterial isolate, genomic DNA only; for further details, see [13]. The analysis was based on a Mauve alignment for colinear genomes. Genomes were generated by DNA sequencing and mapping of DNA reads to the genome of F. tularensis ssp. holarctica (Fth) strain LVS (for details, see [19]). For the clustering, the neighbor-joining bootstrap method was used, with F. tularensis ssp. holarctica (Fth) strain OSU18 as an outgroup