title: Dissemination of bloodmeal acquired Rickettsia felis in cat fleas, Ctenocephalides felis.
abstract: BACKGROUND
  Cat fleas, Ctenocephalides felis, are known biological vectors for Rickettsia felis. Rickettsial transmission can be vertical via transovarial transmission within a flea population, as well as horizontal between fleas through a bloodmeal. The previously undescribed infection kinetics of bloodmeal-acquired R. felis in cat fleas provides insight into the R. felis-flea interaction.
  
  
  RESULTS
  In the present study, dissemination of R. felis in previously uninfected cat fleas fed an R. felis-infected bloodmeal was investigated. At weekly intervals for 28 days, rickettsial propagation, accumulation, and dissemination in gut epithelial cells, specifically in the hindgut and the specialized cells in the neck region of midgut, were observed on paraffin sections of infected cat fleas by immunofluorescence assay (IFA) and confirmed by PCR detection of R. felis 17-kDa antigen gene. IFA results demonstrate ingested rickettsiae in vacuoles during early infection of the gut; lysosomal activity, indicated by lysosome marker staining of freshly-dissected gut, suggests the presence of phagolysosome-associated vacuoles. Subsequent to infection in the gut, rickettsiae spread to the hemocoel and other tissues including reproductive organs. Densely-packed rickettsiae forming mycetome-like structures were observed in the abdomen of infected male cat fleas during late infection. Ultrastructural analysis by transmission electron microscopy (TEM) confirmed the presence and infection characteristics of Rickettsia including rickettsial destruction in the phagolysosome, rickettsial division, and accumulation in the flea gut.
  
  
  CONCLUSIONS
  This study intimately profiles R. felis dissemination in cat fleas and further illuminates the mechanisms of rickettsial transmission in nature.
authors.forename: Chutima
authors.initials: C
authors.lastname: Thepparit
authors.forename: Supanee
authors.initials: S
authors.lastname: Hirunkanokpun
authors.forename: Vsevolod L
authors.initials: VL
authors.lastname: Popov
authors.forename: Lane D
authors.initials: LD
authors.lastname: Foil
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Macaluso
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D002371:Cat Diseases / Q000382:microbiology / Q000469:parasitology / Q000635:transmission*; D002415:Cats; D058251:Ctenocephalides / Q000382:microbiology*; D004269:DNA, Bacterial / Q000235:genetics; D005260:Female; D008297:Male; D010588:Phagosomes / Q000382:microbiology / Q000648:ultrastructure; D016133:Polymerase Chain Reaction / Q000662:veterinary; D012282:Rickettsia Infections / Q000635:transmission / Q000662:veterinary*; D041161:Rickettsia felis / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D014617:Vacuoles / Q000382:microbiology / Q000648:ultrastructure
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial