Ultrastructure of Presumed “Candidatus Rickettsia Andeanae” in Amblyomma maculatum (Acari: Ixodidae)

ORCID

Goddard: https://orcid.org/0000-0002-2617-7141

MSU Affiliation

College of Veterinary Medicine; Department of Basic Sciences; College of Agriculture and Life Sciences; Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology

Creation Date

2026-09-30

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.

Keywords

Amblyomma maculatum, Candidatus Rickettsia andeanae, spotted fever group rickettsiae, transmission electron microscopy

Publication Date

11-1-2014

Publication Title

Journal of Medical Entomology

Publisher

Oxford University Press; Entomological Society of America

First Page

1317

Last Page

1321

Creative Commons License

Creative Commons Attribution-NonCommercial 4.0 International License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License

Rights

© 2014 Entomological Society of America

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Digital Object Identifier (DOI)

https://doi.org/10.1603/ME14132