Molecular detection of Rickettsia felis and Candidatus Rickettsia Asemboensis in fleas from human habitats, Asembo, Kenya

Jiang, J. et al. (2013) Molecular detection of Rickettsia felis and Candidatus Rickettsia Asemboensis in fleas from human habitats, Asembo, Kenya. Vector-Borne and Zoonotic Diseases, 13(8), pp. 550-558. (doi: 10.1089/vbz.2012.1123)

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The flea-borne rickettsioses murine typhus (Rickettsia typhi) and flea-borne spotted fever (FBSF) (Rickettsia felis) are febrile diseases distributed among humans worldwide. Murine typhus has been known to be endemic to Kenya since the 1950s, but FBSF was only recently documented in northeastern (2010) and western (2012) Kenya. To characterize the potential exposure of humans in Kenya to flea-borne rickettsioses, a total of 330 fleas (134 pools) including 5 species (Xenopsylla cheopis, Ctenocephalides felis, Ctenocephalides canis, Pulex irritans, and Echidnophaga gallinacea) were collected from domestic and peridomestic animals and from human dwellings within Asembo, western Kenya. DNA was extracted from the 134 pooled flea samples and 89 (66.4%) pools tested positively for rickettsial DNA by 2 genus-specific quantitative real-time PCR (qPCR) assays based upon the citrate synthase (gltA) and 17-kD antigen genes and the Rfelis qPCR assay. Sequences from the 17-kD antigen gene, the outer membrane protein (omp)B, and 2 R. felis plasmid genes (pRF and pRFd) of 12 selected rickettsia-positive samples revealed a unique Rickettsia sp. (n=11) and R. felis (n=1). Depiction of the new rickettsia by multilocus sequence typing (MLST) targeting the 16S rRNA (rrs), 17-kD antigen gene, gltA, ompA, ompB, and surface cell antigen 4 (sca4), shows that it is most closely related to R. felis but genetically dissimilar enough to be considered a separate species provisionally named Candidatus Rickettsia asemboensis. Subsequently, 81 of the 134 (60.4%) flea pools tested positively for Candidatus Rickettsia asemboensis by a newly developed agent-specific qPCR assay, Rasemb. R. felis was identified in 9 of the 134 (6.7%) flea pools, and R. typhi the causative agent of murine typhus was not detected in any of 78 rickettsia-positive pools assessed using a species-specific qPCR assay, Rtyph. Two pools were found to contain both R. felis and Candidatus Rickettsia asemboensis DNA and 1 pool contained an agent, which is potentially new.

Item Type:Articles
Additional Information:This is a copy of an article published in Vector-Borne and Zoonotic Diseases © 2013 Mary Ann Liebert, Inc.; Vector-Borne and Zoonotic Diseases is available online at:
Glasgow Author(s) Enlighten ID:Knobel, Mr Darryn and Cleaveland, Professor Sarah
Authors: Jiang, J., Maina, A.N., Knobel, D.L., Cleaveland, S., Laudisoit, A., Wamburu, K., Ogola, E., Parola, P., Breiman, R.F., Njenga, M.K., and Richards, A.L.
College/School:College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
Journal Name:Vector-Borne and Zoonotic Diseases
Publisher:Mary Ann Liebert, Inc. Publishers
ISSN (Online):1557-7759
Copyright Holders:Copyright © 2013 Mary Ann Liebert, Inc.
First Published:First published in Vector-Borne and Zoonotic Diseases 13(8):550-558
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher
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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
500531An integrated epidemiological study of zoonotic pathogens in linked human and animal populations in rural KenyaSarah CleavelandWellcome Trust (WELLCOME)081828/B/06/ZRI BIODIVERSITY ANIMAL HEALTH & COMPMED