title: Ultrastructural and genetic evidence of a reptilian tick, Aponomma hydrosauri, as a host of Rickettsia honei in Australia: possible transovarial transmission.
abstract: In 1993, a novel rickettsia was isolated from the blood of inhabitants of Flinders Island, Australia, with acute febrile illnesses. This rickettsia was found to be a new species of spotted fever group (SFG) rickettsia, eventually named Rickettsia honei. The suspected ectoparasite vector of this rickettsia has yet to be identified. The purpose of this study was to evaluate the presence of this rickettsial species in a suspected tick vector, Aponomma hydrosauri, by DNA sequencing and electron microscopy (EM). Ticks collected from an Australian blue-tongued lizard on Flinders Island and a copperhead snake in Tasmania were demonstrated to be infected with R. honei by PCR, DNA sequencing, and EM. Rickettsiae were found in ultrathin sections of salivary glands, malpighian tubules, and midgut epithelial cells. In a previous study with a R. honei-infected tick from Flinders Island, rickettsiae were found in the nuclei of midgut epithelial cells, and EM also revealed the presence of rickettsiae in the cytosol of oocytes and immature eggs, suggesting transovarial transmission. These results implicate A. hydrosauri as a possible host of R. honei on Flinders Island and Tasmania and also provide evidence favoring transovarial maintenance of R. honei.
authors.affiliation: Department of Pathology and WHO Collaborating Center for Tropical Diseases, University of Texas Medical Branch, Galveston 77555-0609, USA.
authors.forename: Ted
authors.initials: T
authors.lastname: Whitworth
authors.forename: Vsevolod
authors.initials: V
authors.lastname: Popov
authors.forename: Violet
authors.initials: V
authors.lastname: Han
authors.forename: Donald
authors.initials: D
authors.lastname: Bouyer
authors.forename: John
authors.initials: J
authors.lastname: Stenos
authors.forename: Stephen
authors.initials: S
authors.lastname: Graves
authors.forename: Lucy
authors.initials: L
authors.lastname: Ndip
authors.forename: David
authors.initials: D
authors.lastname: Walker
mesh_terms: D000818:Animals; D001315:Australia; D004269:DNA, Bacterial / Q000235:genetics / Q000302:isolation & purification; D004847:Epithelial Cells / Q000382:microbiology / Q000648:ultrastructure; D005260:Female; D006801:Humans; D008297:Male; D008317:Malpighian Tubules / Q000382:microbiology / Q000648:ultrastructure; D010053:Ovary / Q000382:microbiology / Q000648:ultrastructure; D016133:Polymerase Chain Reaction; D012104:Reptiles / Q000469:parasitology; D012281:Rickettsia / Q000235:genetics / Q000302:isolation & purification* / Q000648:ultrastructure; D012282:Rickettsia Infections / Q000145:classification / Q000453:epidemiology*; D012469:Salivary Glands / Q000382:microbiology / Q000648:ultrastructure; D013984:Tick Infestations / Q000662:veterinary; D013987:Ticks / Q000382:microbiology*
chemical_list: D004269:DNA, Bacterial