Murdoch University Tick Research raise new questions
The Australian Department of Health has been waiting for results from Murdoch University and the Karl McManus Foundation funded Sydney University research programs.
Murdoch University have just released their findings which raise more questions than they answer making the Sydney University Research even more significant.
The study identified novel candidate pathogens that warrant further scrutiny in the context of investigating so-called “Lyme-like disease” in Australia. Borrelia relapsing fever and “Candidatus Neoehrlichia” pathogens are being identified in new geographic regions throughout the world and their medical importance is well recognised. The aetiological agent of Australian “Lyme-like” illness has been a source of unresolved debate for many years and the discovery of these organisms in Australian I. holocyclus ticks may provide insights into this medical conundrum. Given the widespread presence of endosymbionts in arthropod vectors of disease, together with the fact that such symbionts may be resident in high numbers, our findings also highlight the potential for discovering important novel arthropodassociated bacteria that are in relatively low abundance.
The results raise new questions about tick-borne pathogens in I. holocyclus ticks.
Murdoch University Tick Research
The Australian paralysis tick (Ixodes holocyclus) is of significant medical and veterinary importance as a cause of dermatological and neurological disease, yet there is currently limited information about the bacterial communities harboured by these ticks and the risk of infectious disease transmission to humans and domestic animals. Ongoing controversy about the presence of Borrelia burgdorferi sensu lato (the aetiological agent of Lyme disease) in Australia increases the need to accurately identify and characterise bacteria harboured by I. holocyclus ticks.
Universal PCR primers were used to amplify the V1-2 hyper-variable region of bacterial 16SrRNA genes present in DNA samples from I. holocyclus and I. ricinus ticks, collected in Australia and Germany respectively. The 16S amplicons were purified, sequenced on the IonTorrent platform, and analysed in USEARCH, QIIME, and BLAST to assign genus and species-level taxonomy. Initial analysis of I. holocyclus and I. ricinus identified that >95 % of the 16S sequences recovered belonged to the tick intracellular endosymbiont “Candidatus Midichloria mitochondrii” (CMM). A CMM-specific blocking primer was designed that decreased CMM sequences by approximately 96 % in both tick species and significantly increased the total detectable bacterial diversity, allowing identification of medically important bacterial pathogens that were previously masked by CMM.
Borrelia burgdorferi sensu lato was identified in German I. ricinus, but not in Australian I. holocyclus ticks. However, bacteria of medical significance were detected in I. holocyclus ticks, including a Borrelia relapsing fever group sp., Bartonella henselae, novel “Candidatus Neoehrlichia” spp., Clostridium histolyticum, Rickettsia spp., and Leptospira inadai.
Abundant bacterial endosymbionts, such as CMM, limit the effectiveness of next-generation 16S bacterial community profiling in arthropods by masking less abundant bacteria, including pathogens. Specific blocking primers that inhibit endosymbiont 16S amplification during PCR are an effective way of reducing this limitation. Here, this strategy provided the first evidence of a relapsing fever Borrelia sp. and of novel “Candidatus Neoehrlichia” spp. in Australia. Our results raise new questions about tick-borne pathogens in I. holocyclus ticks.
Growing evidence of an emerging tick-borne disease that causes a Lyme like illness for many Australian patients
On 12 November 2015, the Senate referred the following matter to the Senate Community Affairs References Committee for inquiry and report:
The growing evidence of an emerging tick-borne disease that causes a Lyme‑like illness for many Australian patients.