High prevalence of Rickettsia africae variants in Amblyomma variegatum ticks from domestic mammals in rural western Kenya: Implications for human health

Alice N. Maina, Ju Jiang, Sylvia A. Omulo, Sally J. Cutler, Fredrick Ade, Eric Ogola, Daniel R. Feikin, M. Kariuki Njenga, Sarah Cleaveland, Solomon Mpoke, Zipporah Ng'ang'a, Robert F. Breiman, Darryn L. Knobel, Allen L. Richards

Research output: Contribution to journalArticlepeer-review

Abstract

Tick-borne spotted fever group (SFG) rickettsioses are emerging human diseases caused by obligate intracellular Gram-negative bacteria of the genus Rickettsia. Despite being important causes of systemic febrile illnesses in travelers returning from sub-Saharan Africa, little is known about the reservoir hosts of these pathogens. We conducted surveys for rickettsiae in domestic animals and ticks in a rural setting in western Kenya. Of the 100 serum specimens tested from each species of domestic ruminant 43% of goats, 23% of sheep, and 1% of cattle had immunoglobulin G (IgG) antibodies to the SFG rickettsiae. None of these sera were positive for IgG against typhus group rickettsiae. We detected Rickettsia africae-genotype DNA in 92.6% of adult Amblyomma variegatum ticks collected from domestic ruminants, but found no evidence of the pathogen in blood specimens from cattle, goats, or sheep. Sequencing of a subset of 21 rickettsia-positive ticks revealed R. africae variants in 95.2% (20/21) of ticks tested. Our findings show a high prevalence of R. africae variants in A. variegatum ticks in western Kenya, which may represent a low disease risk for humans. This may provide a possible explanation for the lack of African tick-bite fever cases among febrile patients in Kenya.

Original languageEnglish (US)
Pages (from-to)693-702
Number of pages10
JournalVector-Borne and Zoonotic Diseases
Volume14
Issue number10
DOIs
StatePublished - Oct 1 2014
Externally publishedYes

Keywords

  • African tick-bite fever
  • Ambylomma variegatum
  • Rickettsia africae
  • Tick-borne spotted fever group

ASJC Scopus subject areas

  • Microbiology
  • Infectious Diseases
  • Virology

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