Human Infection with Candidatus Neoehrlichia mikurensis, China

Hao Li¹, Jia-Fu Jiang¹, Wei Liu¹, Yuan-Chun Zheng, Qiu-Bo Huo, Kun Tang, Shuang-Yan Zuo, Kun Liu, Bao-Gui Jiang, Hong Yang, and Wu-Chun Cao

Author affiliations: Beijing Institute of Microbiology and Epidemiology, Beijing, People’s Republic of China (H. Li, J.-F. Jiang, W. Liu, K. Tang, S.-Y. Zuo, K. Liu, B.-G. Jiang, H. Yang, W.-C. Cao); and Mudanjiang Forestry Central Hospital, Mudanjiang, People’s Republic of China (Y.-C. Zheng, Q.-B. Huo)

Abstract

To identify Candidatus Neoehrlichia mikurensis infection in northeastern China, we tested blood samples from 622 febrile patients. We identified in 7 infected patients and natural foci for this bacterium. Field surveys showed that 1.6% of ticks and 3.8% of rodents collected from residences of patients were also infected.

Candidatus Neoehrlichia mikurensis was detected in 1999 in Ixodes ricinus ticks in the Netherlands and referred to as an Ehrlichia spp.–like agent (1). It was then classified as a new member of family Anaplasmataceae on the basis of ultrastructure and phylogenetic analysis (2). The agent was detected in ticks and small wild mammals in Europe and Asia (1–6) and has recently been reported to infect humans, especially immunocompromised patients in Europe (7–10). However, no cases of infection have been identified outside Europe. Moreover, the agent has not yet been isolated in pure culture, and its antigens are not available.
To investigate human infections with tick-borne agents in China, we initiated a surveillance study at Mudanjiang Forestry Central Hospital (Mudanjiang, China). This hospital is one of the largest hospitals treating patients with tick-borne infectious diseases in northeastern China, where various tick-borne agents have been detected in ticks and animal hosts (11–15).

The Study

Figure 1

Thumbnail of Location of Mudanjiang, Heilongjiang Province, China, where Candidatus Neoehrlichia mikurensis was detected.

Figure 1. . . . Location of Mudanjiang, Heilongjiang Province, China, where Candidatus Neoehrlichia mikurensis was detected.

During May 2–July 30, 2010, a total of 622 febrile patients, who had histories of recent tick bites and sought treatment at Mudanjiang Forestry Central Hospital (Figure 1) were screened for the infections of tick-borne agents. When patients were admitted, peripheral blood samples were collected and treated with EDTA. DNA as extracted by using the QIAmp DNA Blood Mini Kit (QIAGEN, Germantown, MD, USA).
For a broad-range assay, a nested PCR specific for the 16S rRNA gene (rrs) was used to detect organisms in the family Anaplasmataceae. For positive samples, 2 heminested PCRs were used to amplify the entire rrs gene. For further confirmation, a nested PCR specific for the 60-kDa heat shock protein gene (groEL) was performed. Detailed cycling conditions for all amplifications are described in the Technical Appendix