title: Ultrastructure of Presumed "Candidatus Rickettsia Andeanae" in Amblyomma maculatum (Acari: Ixodidae).
abstract: Amblyomma maculatum Koch, 1844 (also known as the Gulf Coast tick) is found in parts of the Americas, including the central and southern United States. Its primary importance is as the vector of Rickettsia parkeri, a spotted fever group rickettsia that causes an illness similar to, but milder than, Rocky Mountain spotted fever. A second spotted fever group rickettsia, "Candidatus Rickettsia andeanae," was detected in Gulf Coast ticks approximately 10 yr ago. However, the significance of this organism, including pathogenicity, has not yet been well-characterized. Here, we use transmission electron microscopy to describe bacteria within the tissues of A. maculatum ticks that were positive by polymerase chain reaction assay for "Ca. R. andeanae." In ultrathin sections of unfed A. maculatum adult females, we found evidence of bacteria with morphological features consistent with spotted fever group rickettsiae, including small size (≈0.3 by 0.9 μm), a halo zone (electron-lucent layer around the bacterium), and a trilaminar cell wall. In female ticks, bacteria were present in granular salivary glands and ducts, foregut, Malpighian tubules, nerve trunks, and reproductive tissue. These findings demonstrate evidence of "Ca. R. andeanae" in situ and contribute to our understanding of this novel rickettsia in A. maculatum.
authors: Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, 240 Wise Center Drive, Mississippi State, MS 39762, USA.
authors: F A G
authors: FA
authors: Ferrari
authors: Department of Biochemistry, Molecular Biology, Entomology & Plant Pathology, 100 Old Hwy 12, Mississippi State University, Mississippi State, MS 39762, USA.
authors: J
authors: J
authors: Goddard
authors: Rickettsial Zoonoses Branch, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, 1600 Clifton Rd., Atlanta, GA 30333, USA.
authors: C D
authors: CD
authors: Paddock
authors: Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, 240 Wise Center Drive, Mississippi State, MS 39762, USA. stokes@cvm.msstate.edu.
authors: A S
authors: AS
authors: Varela-Stokes
mesh_terms: D000818:Animals; D005260:Female; D026863:Ixodidae / Q000382:microbiology*; D046529:Microscopy, Electron, Transmission; D012281:Rickettsia / Q000648:ultrastructure*
keywords: spotted fever group rickettsiae; transmission electron microscopy; “Candidatus Rickettsia andeanae,” Amblyomma maculatum