Rickettsia asembonensis is a flea-related Rickettsia with unknown pathogenicity to humans. We detected R. asembonensis DNA in 2 of 1,153 human blood samples in Zambia. Our findings suggest the possibility of R. asembonensis infection in humans despite its unknown pathogenicity.
Rickettsia asembonensis is a fleabome rickettsia closely related to Rickettsia felis and is thus referred to as an R. felis-like organism. R. asembonensis was first detected in cat fleas in Kenya and subsequently reported worldwide (2,2). Although R. felis has been increasingly recognized as a human infective agent that can cause human febrile disease, the infectivity and pathogenicity of R. asembonensis in humans is largely unknown. Recent investigations in patients with febrile illness and petechial lesions identified R. asembonensis DNA and antibodies for rickettsial antigens in Malaysia (3,4). Furthermore, R. asembonensis was isolated in cellular cultures from patients in Peru with acute febrile illness and confirmed by sequencing (5). These reports suggest the possibility of R. asembonensis as a human infective agent. However, no direct evidence of R. felis and R. asembonensis as an etiologic agent of human illness has been established. A previous study in Zambia revealed the predominant existence of R. asembonensis and R. felis in cat fleas (6). Our study investigates the presence of these rickettsiae in human blood in Zambia.
We obtained 753 residual patient blood samples from hospitals in urban Lusaka (n = 519) and the Chongwe District (n = 234) of Zambia. Approximately half of the samples (303/753) were traceable to clinical records of patients. The common clinical conditions among those patients included fever, anemia, meningitis, septicemia, and sickle cell anemia (Appendix Table 1, https://wwwnc.cdc.gov/EID/ article/27/8/20-3467-App1.pdf). In addition, we obtained dried blood spots on Whatman FTA classic cards (Millipore Sigma, https://www.sigmaaldrich. com) from healthy volunteers from rural eastern (n = 200) and central (n = 200) provinces to assess rickettsia infection in healthy rural persons. The study was approved by the National Health Research Authority of Zambia through the Biomedical Research Ethics Committee (reference no. 007-10-18).
We extracted genomic DNA and subjected it to PCR screening that targeted the citrate synthase gene (gltA) of...