On Tuesday 9 July I’m presenting some work at the Australian Mammal Society conference at the University of NSW. The title of my presentation is “The role of macropods in mosquito-borne disease: Implications for urban development and wetland rehabilitation” (my coauthors are Stephen Doggett (Medical Entomology, Westmead Hospital) and Mark Ferson (University of NSW/NSW Health).
Ross River virus causes around 5,000 cases of reported human disease every year but, as the symptoms can sometime be mild, the official data is probably an underestimate. The role of Australian wildlife in mosquito-borne transmission cycles is often overlooked. The emphasis is generally placed on mosquito populations and their relationship to environmental drivers of population abundance. We have some very good data on the types of mosquitoes responsible for transmitting RRV thanks to detection of the virus in wild caught mosquito populations and “vector competence” experiments in the laboratory.
There have only been a few studies looking at the role of wildlife. These studies have included serological surveys, isolation of pathogens from wildlife and laboratory studies investigating the titre and duration of viremia in infected animals. These studies have helped identify macropods as some of the key reservoir hosts of RRV in coastal Australia. However, we still don’t know much about how the local wildlife, mosquitoes and pathogens interact under the influence of local environmental and climatic conditions. In particular, how does the ecology of local macropods influence local mosquito-borne disease risk? To be even more specific, how may the conservation strategies of local wildlife at the urban fringe influence public health risks?
My presentation will concentrate on mosquito abundance and diversity, as well as the activity of mosquito-borne pathogens, from two estuarine river systems in Sydney. The Parramatta River and Georges River systems contain comparable mosquito habitat dominated by estuarine wetlands (i.e. saltmarsh and mangroves) but support very different populations of macropods. There aren’t any macropods along the Parramatta River. What we’ve found by studying these two systems can be used to assist in urban development plans where wildlife conservation may require increased awareness of mosquito population management.
Of course, I’m not suggesting that the conservation of macropods isn’t important. The point here is that local authorities must be aware that in regions where there are opportunities for interactions between mosquitoes and wildlife (particularly kangaroos and wallabies), public health risks will be higher. Increased mosquito populations in association with newly constructed or rehabilitated wetlands, particularly in urban areas, may risk only increase nuisance-biting impacts. However, at the fringes of our cities, the risks of disease caused by pathogens such as RRV must be considered. In these circumstances, mosquito management strategies should be more carefully considered.
The full abstract of my presentation is below:
Mosquito-borne disease risk in coastal regions of Australia is a concern for local authorities. Many gaps exist in our understanding of the drivers of mosquito-borne disease risk, particularly with regard to the role of interactions between mosquitoes and wildlife. Macropods have been identified as important reservoir hosts of mosquito-borne pathogens and the presence of kangaroos and/or wallabies is a critical factor in driving outbreaks of disease. What are the implications for urban development and wetland rehabilitation projects? To investigate the role of macropods in urban mosquito-borne disease outbreaks, mosquitoes and activity of Ross River virus (RRV) was investigated in two estuarine wetland systems in Sydney. The abundance and diversity of mosquitoes produced by the estuarine wetlands along the Parramatta River and Georges River are similar with the dominant mosquito Aedes vigilax. There are no macropods are present along the Parramatta River. Few isolations of RRV have been detected along the Parramatta River but significantly higher rates of RRV (as well as other mosquito-borne pathogens) have been detected from mosquitoes collected along the Georges River. In addition, public health investigation confirmed local acquisition of RRV disease in residents living along the Georges River. No locally acquired RRV disease has been confirmed from the Parramatta River region. The use of natural bushland wildlife corridors along the George’s River by macropods is increasing local disease risk in that region. The results have implications for urban planning where wetland creation and rehabilitation, as well as wildlife corridors, may increase local public health risks.
The full program for the Australian Mammal Society conference is available here.
UPDATE: There was a nice article by Nicky Phillips in the Sydney Morning Herald on 13 July covering this story too “Urban kangaroos, wallabies harbour Ross River virus“