Potential uses in Australia

Australia has a unique environment with highly diverse flora and fauna that have evolved in relative physical isolation over a long time period. A number of pests, diseases and invasive species that Australia has acquired from other parts of the world do not have close relatives in this country. This genetic differentiation and our well-established governance frameworks may make Australia an attractive setting in which to test synthetic gene drives that target pest species.

Any release of an organism containing a synthetic gene drive would be required to comply with our governance arrangements which include the requirement for a comprehensive risk assessment.

Australia has had mixed success in using deliberate biological introductions to reduce invasive and feral species populations. One success story is the control of prickly pear, a cactus which was introduced to Australia in 1788 and quickly became an invasive species spreading rapidly throughout eastern Australia. A South American insect, Cactoblastis cactorum, was introduced as a biological control and successfully reduced the prickly pear population. Other introductions, particularly that of cane toads to suppress cane beetles, have had far greater negative consequences than their modest positive contribution in the sugar cane fields. Mechanisms used for screening and testing biological control agents have prevented a repeat of such destructive introductions in the last few decades, highlighting the efficacy of Australia’s strong governance framework.

There are many potential local and international applications of gene drives in areas such as public health (specifically looking at interactions with pathogens), environmental conservation and agriculture, targeting both animals and plants. Gene drives can provide significant positive benefits to certain problems, especially where alternative methods are ineffective, damaging to the environment and/or costly. Australian-specific examples are described below; more detail is provided in Appendix 2.

Disease applications

Insect-borne infectious diseases are a serious and significant global public health issue, and Australia is not immune. Malaria, dengue, Ross River fever (named after its place of discovery in Queensland) and Zika are all spread by mosquitoes and despite research efforts vaccines are still many years away from being widely available. Other methods to control mosquito populations are in jeopardy due to an increase in insecticide resistance. Current research in Australia is investigating how to suppress the transmission of dengue: a disease estimated to infect 390 million people each year worldwide (Bhatt et al., 2013) and which occurs in parts of northern Australia. Using a natural or synthetic gene drive to reduce mosquito populations, or make the mosquitoes less susceptible to becoming carriers, would help reduce the spread of this disease.

Other potential disease control applications include gene drives in vector insects to prevent the spread of livestock diseases such as blue tongue virus and systems to reduce wildlife diseases such as avian malaria that threaten endangered species.

Problem Examples of current solutions Potential problems with current solutions Potential beneficial consequences of gene drive
Insect-borne diseases Spraying of chemicals, vaccination, wear long sleeve clothing, mosquito nets. Several hundred thousand humans die every year from mosquito-borne diseases. Spraying of non-selective chemicals damages the environment and kills beneficial insects. Current non-chemical solutions rely on changes in human behaviour. Many solutions are costly to implement in remote regions. A gene drive designed to prevent a mosquito from transmitting a pathogen would have positive consequences by reducing the spread of disease. The mosquito would still be present to retain its ecological function. Suppression of populations of exotic mosquitoes and midges will likely have few detrimental effects.

Invasive species and the environment

Introduced invasive species can devastate native flora and fauna through predation, competition or parasitism. Gene drives may have the potential to restore native biodiversity through a number of routes, either by controlling specific invasive species or conferring competitive advantages on native animals. In Australia, suggestions to date include a synthetic gene drive to reduce the population of black rats on Lord Howe Island, cane toads in the tropics, European carp in the Murray Darling Basin and rabbits across the continent.

Problem Examples of current solutions Potential problems with current solutions Potential beneficial consequences of gene drive
Invasive species Traps and poisons, and other vector control strategies (e.g. ballast water exchange). Invasive plants and animals predate and out-compete native Australia flora and fauna. Inaction could result in the extinction of native species. Some traps and poisons are non-selective and vector control strategies can be costly to implement. A gene drive to control an invasive species could restore native species populations and ecosystem function.

Agricultural applications

Australian agriculture is a promising area for gene drive applications. Controlling organisms that damage important crops or carry crop diseases would provide a major boost to agricultural productivity and competitiveness. Introducing genes that reverse pesticide or herbicide resistance would help farmers to continue to control insects and weeds by chemical methods.

Suppressing or modifying invertebrate pests would be valuable for farmers and land managers. Targets for suppression include fruit fly pests, which attack soft fruits and cause significant crop loss, as well as various moths, mites, thrips and other pest invertebrates which attack vegetables and broad acre crops. Pests like diamondback moths, Lucilia blowflies and redlegged earth mites that have developed resistance to chemical pesticides are particularly important targets for control. Synthetic gene drives might also be developed to modify insect and mite vectors to reduce their ability to transmit plant viruses.

Problem Examples of current solutions Potential problems with current solutions Potential beneficial consequences of gene drive
Agricultural pests Spraying of pesticides. Spraying of chemicals damages biodiversity and decreases beneficial invertebrates due to non-selective nature of many chemicals. Pesticides become ineffective when resistance evolves. A gene drive to eliminate a weed or pest could reduce chemical spraying and potentially increase farmer’s crop yields.

© 2019 Australian Academy of Science