Molecular Evidence of Novel Spotted Fever Group <i>Rickettsia</i> Species in <i>Amblyomma albolimbatum</i> Ticks from the Shingleback Skink (<i>Tiliqua rugosa</i>) in Southern Western Australia

• Main Authors: Mythili Tadepalli, Gemma Vincent, Sze Fui Hii, Simon Watharow, Stephen Graves, John Stenos
• Format: Article
• Language: English
• Published: MDPI AG 2021-01-01
• Series: Pathogens
• Subjects: <i>Rickettsia</i>; infectious diseases; reptile; molecular epidemiology
• Online Access: https://www.mdpi.com/2076-0817/10/1/35

Tick-borne infectious diseases caused by obligate intracellular bacteria of the genus <i>Rickettsia</i> are a growing global problem to human and animal health. Surveillance of these pathogens at the wildlife interface is critical to informing public health strategies to limit their impact. In Australia, reptile-associated ticks such as <i>Bothriocroton hydrosauri</i> are the reservoirs for <i>Rickettsia honei</i>, the causative agent of Flinders Island spotted fever. In an effort to gain further insight into the potential for reptile-associated ticks to act as reservoirs for rickettsial infection, <i>Rickettsia</i>-specific PCR screening was performed on 64 <i>Ambylomma albolimbatum</i> ticks taken from shingleback skinks (<i>Tiliqua rugosa</i>) located in southern Western Australia. PCR screening revealed 92% positivity for rickettsial DNA. PCR amplification and sequencing of phylogenetically informative rickettsial genes (<i>ompA, ompB, gltA, sca4,</i> and <i>17kda</i>) suggested that the single rickettsial genotype detected represented a novel rickettsial species, genetically distinct from but closely related to <i>Rickettsia gravesii</i> and within the rickettsia spotted fever group (SFG). On the basis of this study and previous investigations, it would appear that <i>Rickettsia</i> spp. are endemic to reptile-associated tick species in Australia, with geographically distinct populations of the same tick species harboring genetically distinct SFG <i>Rickettsia</i> species. Further molecular epidemiology studies are required to understand the relationship between these diverse <i>Rickettsiae</i> and their tick hosts and the risk that they may pose to human and animal health.