Open AccessCotransmission of Divergent Relapsing Fever Spirochetes by Artificially Infected Ornithodoros hermsi
Author(s) -
Paul F. Policastro,
Sandra J. Raffel,
Tom G. Schwan
Publication year - 2011
Publication title -
applied and environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.552
H-Index - 324
eISSN - 1070-6291
pISSN - 0099-2240
DOI - 10.1128/aem.05830-11
Subject(s) - biology , ornithodoros , tick , virology , microbiology and biotechnology , borrelia , borrelia burgdorferi , genetics , antibody
The soft tickOrnithodoros hermsi , which ranges in specific arboreal zones of western North America, acts as a vector for the relapsing fever spirocheteBorrelia hermsii . Two genomic groups (genomic group I [GGI] and GGII) ofB. hermsii are differentiated by multilocus sequence typing yet are codistributed in much of the vector's range. To test whether the tick vector can be infected via immersion, noninfected, colony-derivedO. hermsi larvae were exposed to reduced-humidity conditions before immersion in culture suspensions of several GGI and GGII isolates. We tested for spirochetes in ticks by immunofluorescence microscopy and in mouse blood by quantitative PCR of thevtp locus to differentiate spirochete genotypes. The immersed larval ticks were capable of spirochete transmission to mice at the first nymphal feeding. Tick infection with mixed cultures of isolates DAH (vtp-6 ) (GGI) and MTW-2 (vtp-5 ) (GGII) resulted in ticks that caused spirochetemias in mice consisting of MTW-2 or both DAH and MTW-2. These findings show that this soft tick species can acquireB. hermsii by immersion in spirochete suspensions, that GGI and GGII isolates can coinfect the tick vector by this method, and that these spirochetes can be cotransmitted to a rodent host.