Vector and Waterborne Pathogens Group

Our Research

Our research has concentrated on the molecular detection and epidemiology of vector and water-borne pathogens. This includes some of the following areas:

Vector-Borne Diseases

The molecular epidemiology of tick-transmitted blood parasites and bacterial infections of companion animals, wildlife and people in Australasia is an area that is poorly understood and has potential implications for human health. Although we have long experience in veterinary aspects of vector-borne diseases, for the last few years or research has focused increasingly on questions concerning possible tick-borne infections in people.

We have recently concluded our Pilot Study into tick-borne microorganisms from people with chronic illness attributed to tick bite.

Our team publishes widely on vector-borne diseases (see publication lists for each of the team members) and the team leaders have provided expert opinion and advice to the Chief Medical Officer’s Clinical Advisory Committee on Lyme Disease (now disbanded), and parliamentary hearings including the 2016 Senate Hearing into tick-borne illness in Australia. We also discuss our research findings at national and international conferences. Furthermore we have engaged with a number of media platforms (TV - ABC Catalyst and SBS Insight, radio, print, online) discussing our research.

Our funding for these studies has come predominantly from two Australian Research Council (ARC) Linkage Projects, with Industry Partners Bayer Australia and Bayer Animal Health (Germany), and we work closely with research colleagues at the University of Sydney, University of Queensland, and Queensland Health, as well as many other researchers and doctors in Australia and around the world. We are also grateful for individual donations to our research (see here for details), and for a recent very generous donation from the Country Women’s Association (CWA) via the Lyme Disease Association of Australia (LDAA) (read here).

Our strategy

Key research findings and progress to date include:

• We have received between 10,000-20,000 ticks from collectors living all over Australia. The ticks themselves have been removed from companion animals, wildlife and people, or in some cases have been caught off the ground (unattached, questing). Prior to the start of our research there was concern that overseas ticks, such as those responsible for the transmission of Lyme disease in other countries, may have been introduced and become ‘established’ in Australia. We have found no evidence for this.

• We have established and thoroughly tested a ‘molecular toolkit’ for the detection of minute amounts of target DNA. Our targets are the bacteria, protozoa and viruses inside ticks (and other samples). The toolkit is based on the latest molecular technologies referred to as deep sequencing (or next generation sequencing, NGS).

• Two species of native tick; the paralysis tick (Ixodes holocyclus) in Eastern Australia and the ornate kangaroo tick (Amblyomma triguttatum) in the west are responsible for the vast majority of tick bites of people in Australia. There are certainly other ticks that bite people occasionally, but much less frequently as far as our data shows.

• The Australian tick species that we have examined using our molecular toolkit contain many different species and types of microorganisms, including bacteria (the most abundant), parasites (protozoa), and viruses. Collectively these organisms inside ticks are referred to as their “microbiome” (or “microbiota”). (In different tick species overseas some organisms within those ticks’ microbiomes are known to be pathogenic (i.e. cause disease in people). To date, with the exception of Coxiella and Rickettsia species, we have not discovered any known tick-borne pathogens amongst these microorganisms.)

• We have however discovered many new species of microorganisms in the Australian ticks studied so far that are related to those known pathogens in the northern hemisphere. Amongst the groups of bacteria that we have identified are Anaplasma, Babesia, Ehrlichia, Francisella, Neoehrlichia and Borrelia. We are working hard to further classify these organisms and to understand whether they could be transmitted to people (and animals) in Australia and if they can cause disease.

• It is important to emphasise that we have not found in Australia any evidence of Borrelia burgdorferi (sensu lato), the cause of Lyme borreliosis overseas. However, importantly, Dr Oskam and PhD Student Kimberly Loh have found a new type of Borrelia in ticks from echidnas in NSW and Qld, but like the other organisms, it is only distantly related to the causative agents of Lyme borreliosis. They have since named it Borrelia tachyglossi and so far we do not know if it causes illness in echidnas, let alone people.

• We also reported on a study using dogs as sentinels for infection by pathogens of humans, notably the cause of Lyme borreliosis. (Essentially dogs act as ‘early warning’ for a vector borne disease in people, since they get bitten more frequently than humans by ticks in an area, and will therefore develop antibodies to any infectious organism carried by those ticks.) We tested 555 dogs from four groups: (1) dogs living in the Northern Beaches area of Sydney (a ‘hotspot’ for paralysis ticks and reported illness in people), (2) dogs owned by people with a diagnosis of ‘Lyme disease-like illness’, (3) foxhounds used for the commercial production of antivenom to the paralysis tick, and (4) a control group of dogs living in an indigenous community in northern WA, where there are no paralysis ticks). We did not find any evidence in these dogs for locally-acquired Lyme borreliosis (or any other zoonotic tick-borne pathogen). Additionally, it is important to note that the group of foxhounds had collectively been bitten by an estimated 160,000 paralysis ticks, collected from coastal NSW and Qld. None of them was positive for Lyme borreliosis. We believe that this is the strongest evidence yet that classical Lyme borreliosis, as known in the northern hemisphere, does not occur in Australia. At the very least it is not transmitted by the paralysis tick, which as noted, is the most common biter of people in the eastern states. Given that we have unique tick species in Australia, it is much more likely that the unique bacteria and other microorganisms that they carry are candidates for the cause of disease in Australian humans.

• In 2012, Prof. Irwin was involved in the identification of zoonotic babesiosis (Babesia microti), known previously only in the Northern Hemisphere, in a person from the NSW south coast with no travel history.

• Other recent PhD projects undertaken include examination of novel Trypanosoma species in native animals (quokkas and Gilbert’s potoroos) by Dr Jill Austen, trypanosomes in Koalas (by Linda McInnes), and a current study by Amanda Duarte Barbosa has been studying vector-borne parasites in marsupials all around Australia.

Molecular epidemiology/taxonomy of protozoan parasites

We are currently working on an ARC-Funded project entitled: Innovative approaches to understanding and limiting the public health risks of Cryptosporidium and Giardia in animals in Australian catchments (Linkage Project LP130100035).

Cryptosporidium & Giardia (C&G) are the major public health concern of water utilities & are responsible for disease in a wide range of hosts, 95.5% of waterborne protozoan outbreaks worldwide, can be fatal in the immunocompromised and are resistant to chlorine. This proposal will target a key knowledge gap; the lack of quantitative data on human infectious sp. It will analyse C&G in animals and human sewage in catchments across 3 states (WA, NSW and Qld), identify the species/ subtypes, the percentage viability and develop improved modelling and quantitative microbial risk assessments (QMRA). The project will result in the development of more targeted, cost-effective measures to minimise exposures to infections, accurate risk assessment, & scientific catchment management.

Prof. Ryan also collaborates with A/Prof. Alan Lymbery on the molecular epidemiology of Cryptosporidium and other parasites in fish.

We also have a MLA-funded project in collaboration with A/Prof. David Millar working on a project entitled “Causes of scouring and ill-thrift in Rangeland goats”.
The Australian goatmeat industry has experienced strong growth over the past 20 years and this growth has been largely supported by the sale of goats derived from rangeland or extensive production systems. Of the 1.5 million goats now slaughtered annually, approximately 90 percent are rangeland goats. Relocating goats into close confinement situations can disrupt their social structure and dominance behaviour. In addition, poor nutrition, lack of shelter, overcrowding and excessive handling can lead to further stress, which aids the development of disease. Little is known about their prevalence and contribution to scouring in rangeland goats in Australia. This project is being undertaken by Khalid Al Habsi as part of his PhD thesis and will investigate parasitic and bacterial causes of scouring in rangeland goats. Sylvia Afriyea has just commenced her PhD in Jan 2014 working on a project entitled “Enhancing livestock productivity through the molecular epidemiology of Cryptosporidium as emerging zoonoses in Ghana”.

Previous studies

Previous research included a Meat and Livestock Australia (MLA)-funded project entitled “Impact of bacteria and coccidia on scouring & productivity in sheep”. Scouring and dag in sheep and subsequent breech blowfly strike is a major and widespread economic and animal welfare problem for the Australian sheep industry, yet the causes of scouring in sheep remain poorly understood. This project involved the development of molecular tools to examine if scouring and production loss is associated with particular protozoan or bacterial species/genotypes and with particular management systems under Australian conditions. The project was run by Dr. Rongchang Yang

In collaboration with colleagues at Curtin University, Prof. Ryan was part of an ARC-Linkage project entitled “Understanding wastewater treatment technologies for alternative water use: transformation of inorganic and organic nitrogen” - LP130100602. Reuse of treated wastewater for non-potable purposes is an important water management strategy in many parts of rural Australia, however industry uptake is hampered by a lack of knowledge of the chemical and microbial risks of alternative uses of treated wastewater. This study aimed provide a new understanding of the chemistry of inorganic and organic nitrogen removal in rural wastewater treatment systems, and use novel molecular tools to profile the microbial community in wastewater before and after treatment. Improved knowledge of wastewater treatment process efficacy will improve compliance with health guidelines, protect public and environmental health, and enable an increased uptake of alternative water use options in rural Australia.