【medical-news】NEJM：军事医学科学院曹务春等发现新发蜱媒立克次体病（一）

Human Infection with Candidatus Rickettsia tarasevichiae
N Engl J Med 2013; 369:1178-1180September 19, 2013 DOI: 10.1056/NEJMc1303004
To the Editor:
From May through August 2012, a total of 251 patients who had recent tick bites sought treatment at Mudanjiang Forestry Central Hospital in northeastern China and were tested for tickborne infections. Polymerase-chain-reaction testing followed by sequencing of eschar and blood samples showed that 5 patients were infected with Candidatus Rickettsia tarasevichiae, a new species of rickettsiae of the spotted fever group. Phylogenetic analysis based on either the citrate synthase gene or the outer-membrane protein A gene showed that the agent was genetically close to R. canadensis (see Fig. 1 in the Supplementary Appendix , available with the full text of this letter at NEJM.org), one of several “ancestral” rickettsiae that are suspected to be endosymbionts and nonpathogens. In an indirect immunofluorescence assay, IgM or IgG antibodies reacted to two endemic species of rickettsiae of the spotted fever group, R. heilongjiangensis and R. sibirica.
The study of these cases was approved by the institutional review board of the Chinese Academy of Military Medical Sciences. All patients provided written informed consent.
Characteristics of the five patients are shown in Table 1 TABLE 1

Clinical Characteristics and Laboratory Test Results of the Five Patients withCandidatus Rickettsia tarasevichiaeInfections on Admission.. All five patients had a recent tick bite and no documented immunocompromised conditions. Their ages ranged from 12 to 56 years (median, 30 years), and three were women. They were hospitalized with fever (in two patients), asthenia (in three patients), anorexia (in three patients), nausea (in three patients), headache (in three patients), eschar (in three patients) (Fig. 2 in the Supplementary Appendix ), and lymphadenopathy (in two patients). Patient 5 had meningitis-like manifestations such as vomiting, neck stiffness, and Kernig's sign. Coma, renal dysfunction, and respiratory acidosis then developed, and the patient died 4 days after admission to the hospital. Laboratory tests showed a slight increase in the leukocyte count (in three patients), an elevated level of aspartate aminotransferase (in one patient), proteinuria (in one patient), and an increase in the level of cerebrospinal fluid protein and leukocyte count in Patient 5 (Table 1 ). Since none of the patients presented with rash, which is considered to be a typical sign of infections with species of rickettsiae of the spotted fever group in China, their conditions were initially misdiagnosed, and they received penicillin G, leading to a prolonged hospitalization for approximately 20 days. To identify local natural foci, host-seeking ticks were collected around the patients' residences. A total of 46 of 453 Ixodes persulcatus ticks (10%) were positive for Candidatus R. tarasevichiae.
Candidatus R. tarasevichiae was initially detected in I. persulcatus ticks in various regions of Russia. We identified the agent as an emerging pathogen causing human infection. These findings underscore the concept that rickettsioses are more common than previously realized and may be associated with misdiagnosed causes of fever globally. Careful attention to clinical features and the use of molecular diagnostic tools could be helpful in establishing an etiologic diagnosis that may facilitate appropriate treatment and public health measures.