Neurological Presentations Caused By Rickettsia Felis Infection

A 24- year-old man who lived in Ningbo was admitted to hospital with sudden onset twitching of the extremities. His family reported that the patient was previously healthy and did not have any history of epilepsy; however, the patient was a pet lover who owned three dogs, and came into contact with stray dogs and cats. His temperature was 38.0 degrees C, blood pressure 154/84 mmHg (without vasopressor support) and he had a regular pulse at 117/ min. Examination revealed unconsciousness (Glasgow coma scale of 6), and a few inconspicuous maculopapular erythematous rashes on and around his neck (3-5 mm diameter). There were no focal neurological findings or neck stiffness. A routine blood test revealed a left shift with a high percentage of polymorphonuclear leukocytes (83.6%). The C-reactive protein level was 92.7 mg/litre (normal range 0-8 mg/litre), and the procalcitonin level was 0.229 ng/ml (normal range 0-0.046 ng/ml). Lumbar puncture was performed and the CSF was clear and colourless with a cell count of 8 cells/mu l (two lymphocytes, six neutrophils), protein level 0.325 g/litre ( normal range 0.15- 0.45 g/litre), and glucose level 3.6 mmol/litre (normal range 2.5-4.5 mmol/litre). CSF and blood cultures were also performed, and no microorganisms were detected upon Gram staining or during routine culture. Serological testing and polymerase chain reaction for suspected microorganisms (such as Escherichia coli, Vibrio cholerae, Rickettsia and Salmonella spp.) were also conducted but provided no significant clues. A plain computed tomography scan of the head and a chest radiograph were normal. Renal function test values, liver function test values, and electrolyte levels were within the normal ranges. Treatment was initiated using valproate to treat status epilepticus and piperacillin-tazobactam combined with levofloxacin for suspected CNS infection.On the second day of intensive care unit admission, the patient's CSF sample underwent metagenomic next-generation sequencing analysis. This identified eight sequence reads that uniquely corresponded to the R. felis genome, with 0.023% coverage. After removal of human reads, R. felis reads accounted for 0.8% of the microorganisms. R. felis DNA was further verified in the CSF using real- time polymerase chain reaction followed by Sanger sequencing. Based on these results and the past exposure to stray dogs and cats, the patient was diagnosed with R. felis encephalopathy. Oral doxycycline (0.1 g every 12 hours) was prescribed to replace piperacillin-tazobactam and levofloxacin. Subsequently the patient's fever gradually reduced, as did his limb twitches. He emerged from the coma on the fourth day of his intensive care unit admission and was discharged home 6 days later with no further limb twitches.