Screening for Rickettsia, Coxiella and Borrelia Species in Ticks from Queensland, Australia

Hazizul Hussain-Yusuf,Stephen Graves,Mythili Tadepalli,Noel D Preece,John Stenos,Sandra Abell,Naomi Bowie,Kate Mitram,Sze Fui Hii,Gemma Vincent,Amy Shima

doi:10.3390/pathogens9121016

Abstract

Tick bites in Australia are linked to the transmission of a variety of infectious diseases in humans, livestock and wildlife. Despite this recognition, little is currently known about the variety of potential pathogens that are carried and transmitted by Australian ticks. In this study, we attempted to expand knowledge of Australian tick-borne bacterial pathogens by analyzing various tick species from the state of Queensland for potential human pathogens belonging to the Rickettsia, Coxiella and Borrelia genera. A total of 203 ticks, comprising of four genera and nine different tick species, were screened by specific qPCR assays. An overall Rickettsia qPCR positivity of 6.4% (13/203) was detected with rickettsial DNA found in four tick species (Ixodes holocyclus, I. tasmani, Amblyomma triguttatum, and Haemaphysalis longicornis). Amplification and analysis of several rickettsial genes from rickettsial qPCR positive samples identified sequences closely related to but genetically distinct from several previously described cultured and uncultured rickettsial species in the Rickettsia spotted fever subgroup. No ticks were positive for either Coxiella or Borrelia DNA. This work suggests that a further diversity of rickettsiae remain to be described in Australian ticks with the full importance of these bacteria to human and animal health yet to be elucidated.

Highlights

Ticks are arthropods with a complex life history that involves four stages, three which require a blood meal from a vertebrate animal host prior to metamorphosing into the developmental stage [1,2]
Haemaphysalis species ticks were comprised of Haemaphysalis bancrofti (n = 10), Haemaphysalis humerosa (n = 2), Haemaphysalis longicornis (n = 3), and Haemaphysalis novoguineae (n = 1)
The Rickettsia positive ticks were removed from humans, domesticated animals and several species of wildlife, illustrating the potential for ticks to mediate the transmission of different tick-borne microorganisms across different host groups in this region

Summary

Introduction

Ticks are arthropods with a complex life history that involves four stages, three which require a blood meal from a vertebrate animal host prior to metamorphosing into the developmental stage [1,2]. As a result of this activity, ticks are globally recognized as important vectors of infectious diseases in humans and animals. In Australia, tick bites have been associated with a range of important infectious diseases, including ‘Q fever’ (Coxiella burnetii), Queensland tick typhus (Rickettsia australis), Flinders Island spotted fever (Rickettsia honei) and Australian spotted fever In Australia, species of ticks have been identified, of which 17 are known to bite humans [4,5]. The three species that are considered the most important for transmission of bacterial infections are: (i) the paralysis tick (Ixodes holocyclus), the known vector for Queensland tick typhus and Q fever; (ii) the ornate kangaroo tick (Amblyomma triguttatum), another vector of Q fever and; (iii) the southern reptile tick (Bothriocroton hydrosauri), the vector of Flinders Island spotted fever [1]

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Discussion

Conclusion