A test tube with larvae from Aedes aegypti, the insect vector for dengue, chikungunya, and Zika virus. Image: Flickr/Conred Guatemala.
The World Health Organization (WHO) has in the past week declared that the Zika virus is a global public health emergency.
While this mosquito-borne virus has been around for some 70 years, the global incidence and speed with which it has spread over the past few years, and the recent suggested link to pregnant women and microcephaly in their babies, is concerning.
We have seen an increase in the distribution of vectors – virus-carrying insects such as mosquitoes and midges – and the viruses they carry both globally and within Australia. This is due to a number of factors including increased urbanisation, increased travel and trade, as well as a changing climate.
We sat down with some of our experts to talk about insect-borne viruses, and the threats they pose to animal and human health.
We’ve heard a lot about Zika virus – can you tell us what it is?
John Lowenthal, Research Director CSIRO Health & Biosecurity: Zika is a mosquito-borne virus that was discovered in 1947 but for many years only sporadic human cases were detected in Africa and Southern Asia. The first documented outbreak of Zika virus disease occurred in the Pacific in 2007. Since 2013, cases and outbreaks of the disease have been reported from the Western Pacific, the Americas and Africa, with wide-spread cases reported last year in Brazil.
The Aedes mosquito, which also has the ability to spread dengue, chikungunya and yellow fever, has the ability to transmit Zika virus.
Does CSIRO work with Zika and other insect-borne viruses?
John Lowenthal: We have a deep history studying mosquitoes and other insects that carry and transmit disease-causing viruses that impact the health of people and livestock animals. While we don’t currently work with Zika virus, we have the infrastructure, capabilities and expertise to do so, if needed.
‘To the hilt’ — a mosquito gorging. Image: Flickr/Chris Fifield-Smith
We have an active science program focused on relatives of the virus, those in the same family as Zika (the family Flaviviridae), including the Kunjin strain of West Nile virus, dengue virus and Murray Valley encephalitis virus.
Debbie Eagles, Research Director CSIRO Australian Animal Health Laboratory: As a national facility we play a role in helping to protect Australia’s multi-billion dollar livestock industries. As part of this we work alongside state veterinary laboratories in order to undertake diagnostic testing and surveillance of insect-borne diseases of livestock. We also provide advice to national bodies and authorities to assist in identifying, responding and controlling outbreaks of these diseases. For example, as a member of the National Arbovirus Monitoring Program (NAMP) we assist in monitoring the distribution of bluetongue virus to help ensure market access and trade opportunities for Australian industry to global markets.”
What ways can we tackle mosquitoes and the viruses they carry?
John Lowenthal: One option is vaccination, however no vaccine has been clinically approved for use to date, though extensive research efforts are under way globally to identify treatments to protect people from insect-borne diseases. Another approach to curb infections is managing mosquito populations – for example removing all sources of stagnant water and using targeted insecticide application. This has been successful, however, only for a limited time as many mosquitoes have shown resistance to insecticides.
It’s clear that new and smarter approaches are needed to more effectively manage the mosquito. Our research suggests that it may be possible to reduce a mosquito’s capacity to transmit viruses by manipulating its immune system. For example, we would modify the mosquitoes so they become resistant to infection. This may involve increasing production of antiviral proteins or decreasing production of proteins that help viral growth.
Another approach would be to block entry of the virus into the mosquito by modifying proteins present in its gut. Blocking infection in mosquitoes would break the cycle of transmission and prevent further spread of the virus to people.
What other work related to mosquito-borne viruses does CSIRO do?
Paul De Barro, Research Director Risk Evaluation and Preparedness: We have expertise in a range of areas and work with national and international organisations to help find solutions to mosquito-related problems. For example, we undertake risk analysis research where we’re using complex algorithms to assess the risks posed by different response options.
We’re undertaking research to help design vector-safe communities and as part of this we’re working on what makes a house vulnerable to the mosquitoes that spread viruses. For example, what role do water tanks play in allowing mosquitoes to establish around homes and what factors make a home more or less mosquito-friendly.
We are looking at how we can better respond to the establishment of new mosquito vectors, such as the Asian tiger mosquito, and manage existing mosquito vectors more effectively. Managers need to make decisions about how to respond to mosquito outbreaks and make best use of limited resources — and often have to do so when key information is lacking. We are coming up with ways to help them deal with that uncertainty and to support their decision making. Our researchers are also developing new tools to help manage mosquitoes such as sterilisation, a technology that we’re using to suppress fruit fly populations, but in this case applying it to mosquitoes.
In addition we’re looking at how we can use social media and other sources of data to take a big data approach to strengthen how we identify communities at risk from diseases spread by mosquitoes. And finally, as well as managing mosquitoes, we are also developing new ways to detect the diseases that they transmit. For example, we can now detect the presence of malaria by analysing the breath of people.
Debbie Eagles: We have also developed specific online tools for modelling the wind dispersal of living organisms. Wind plays an important role in contributing to the spread of some of the most serious diseases of livestock, including those with insect vectors. Our software model — TAPPAS — allows us to tap into global meteorological datasets, dispersion models and combine that with biological information on the insect to predict when and where pests might be blown into, and from, Australia.
John Lowenthal: There are still many gaps in our understanding of the complex relationship between mosquitoes, viruses, animals, people and the environment. We need to continue investigating how mosquitoes respond to infection and whether this information can be used to prevent the spread of disease in animal and/or human populations. Control and eradication of insect-borne diseases is a complex problem and requires a coordinated international response.
Debbie Eagles: As I mentioned we have the capability to diagnose a range of insect-borne diseases in livestock and this is an area we will continue to focus on for our livestock industries. In particular we’ll continue to improve and develop future diagnostic tests to help stay ahead of viruses that affect both animals and people.
John Lowenthal: We will remain alert and ready to respond and assist — locally and globally — if called upon.
For further information on the Zika virus situation visit the WHO website. To learn more about our research read a genetic approach to mosquitoes can stop them spreading infections.
Media enquiries contact: Emma Pyers 03 5227 5123