Stowaway mozzies enter Australia from Asian holiday spots – and they’re resistant to insecticides



File 20190320 93051 1rj4pog.jpg?ixlib=rb 1.1
We might not be able to use common insecticides to kill mosquitoes that arrive from other countries.
from www.shutterstock.com

Tom Schmidt, University of Melbourne; Andrew Weeks, University of Melbourne, and Ary Hoffmann, University of Melbourne

Planning a trip to the tropics? You might end up bringing home more than just a tan and a towel.

Our latest research looked at mosquitoes that travel as secret stowaways on flights returning to Australia and New Zealand from popular holiday destinations.

We found mosquito stowaways mostly enter Australia from Southeast Asia, and enter New Zealand from the Pacific Islands. Worse still, most of these stowaways are resistant to a wide range of insecticides, and could spread disease and be difficult to control in their new homes.




Read more:
Why naming all our mozzies is important for fighting disease


Secret stowaways

Undetected insects and other small creatures are transported by accident when people travel, and can cause enormous damage when they invade new locations.

Of all stowaway species, few have been as destructive as mosquitoes. Over the past 500 years, mosquitoes such as the yellow fever mosquito (Aedes aegypti) and Asian tiger mosquito (Aedes albopictus) have spread throughout the world’s tropical and subtropical regions.

Dengue spread by Aedes aegypti mosquitoes now affects tens to hundreds of millions of people every year.




Read more:
Explainer: what is dengue fever?


Mosquitoes first travelled onboard wooden sailing ships, and now move atop container ships and within aircraft.

Adults in your luggage

You probably won’t see Aedes mosquitoes buzzing about the cabin on your next inbound flight from the tropics. They are usually transported with cargo, either as adults or occasionally as eggs (that can hatch once in contact with water).

It only takes a few Aedes stowaways to start a new invasion. In Australia, they’ve been caught at international airports and seaports, and in recent years there has been a large increase in detections.

Aedes aegypti mosquito detections per year at Australian international terminals – passenger airline terminals in white; seaports or freight terminals in black.
Tom Schmidt, Author provided



Read more:
Curious Kids: When we get bitten by a mosquito, why does it itch so much?


In our new paper, we set out to determine where stowaway Aedes aegypti collected in Australia and New Zealand were coming from. This hasn’t previously been possible.

Usually, mosquitoes are only collected after they have “disembarked” from their boat or plane. Government authorities monitor these stowaways by setting traps around airports or seaports that can capture adult mosquitoes. Using this method alone, they’re not able to tell which plane they came on.

But our approach added another layer: we looked at the DNA of collected mosquitoes. We knew from our previous work that the DNA from any two mosquitoes from the same location (such as Vietnam, for example) would be more similar than the DNA from two mosquitoes from different locations (such as Vietnam and Brazil).

So we built a DNA reference databank of Aedes aegypti collected from around the world, and compared the DNA of the Aedes aegypti stowaways to this reference databank. We could then work out whether a stowaway mosquito came from a particular location.

We identified the country of origin of most of the Aedes aegypti stowaways. The majority of these mosquitoes detected in Australia are likely to have come from flights originating in Bali.

Here’s where the Aedes aegypti mozzies come into Australia and New Zealand from.
Tom Schmidt, Author provided

Now we can work with these countries to build smarter systems for stopping the movement of stowaways.

As the project continues, we will keep adding new collections of Aedes aegypti to our reference databank. This will make it easier to identify the origin of future stowaways.

New mosquitoes are a problem

As Aedes aegypti has existed in Australia since the 19th century, the value of this research may seem hard to grasp. Why worry about invasions by a species that’s already here? There are two key reasons.

Currently, Aedes aegypti is only found in northern Australia. It is not found in any of Australia’s capital cities where the majority of Australians live. If Aedes aegypti established a population in a capital city, such as Brisbane, there would be more chance of the dengue virus being spread in Australia.

The other key reason is because of insecticide resistance. In places where people use lots of insecticide to control Aedes aegypti, the mosquitoes develop resistance to these chemicals. This resistance generally comes from one or more DNA mutations, which are passed from parents to their offspring.




Read more:
The battle against bugs: it’s time to end chemical warfare


Importantly, none of these mutations are currently found in Australian Aedes aegpyti. The danger is that mosquitoes from overseas could introduce these resistance mutations into Australian Aedes aegpyti populations. This would make it harder to control them with insecticides if there is a dengue outbreak in the future.

In our study, we found that every Aedes aegpyti stowaway that had come from overseas had at least one insecticide resistance mutation. Most mosquitoes had multiple mutations, which should make them resistant to multiple types of insecticides. Ironically, these include the same types of insecticides used on planes to stop the movement of stowaways.

Other species to watch

We can now start tracking other stowaway species using the same methods. The Asian tiger mosquito (Aedes albopictus) hasn’t been found on mainland Australia, but has invaded the Torres Strait Islands and may reach the Cape York Peninsula soon.

Worse still, it is even better than Aedes aegypti at stowing away, as Aedes albopictus eggs can handle a wider range of temperatures.

A future invasion of Aedes albopictus could take place through an airport or seaport in any major Australian city. Although it is not as effective as Aedes aegypti at spreading dengue, this mosquito is aggressive and has a painful bite. This has given it the nickname “the barbecue stopper”.

Beyond mosquitoes, our DNA-based approach can also be applied to other pests. This should be particularly important for protecting Australia’s A$45 billion dollar agricultural export market as international movement of people and goods continues to increase.




Read more:
Explainer: what is Murray Valley encephalitis virus?


The Conversation


Tom Schmidt, Research fellow, University of Melbourne; Andrew Weeks, Senior Research Fellow, University of Melbourne, and Ary Hoffmann, Professor, School of BioSciences and Bio21 Institute, University of Melbourne

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Advertisements

The battle against bugs: it’s time to end chemical warfare



File 20190215 56220 4e8qzx.jpg?ixlib=rb 1.1
Does it really pay to spray?
Dmitry Syshchikov/Shutterstock

Lizzy Lowe, Macquarie University; Cameron Webb, University of Sydney; Manu Saunders, University of New England, and Tanya Latty, University of Sydney

Insects are important wildlife often overlooked in urban habitats. What we do notice are the cockroaches, ants and mosquitoes in and around our homes. All too often we reach for the insect spray.

But not all insects are pests – a wide variety of them help keep our cities healthy. They pollinate plants, feed other wildlife, recycle our rubbish, and eat other insect pests. Insects are vital to our well-being.

Unfortunately, like many other wild animals, insects are under threat. A recent study warned that 40% of the world’s insect species face the prospect of extinction, amid threats such as climate change, habitat loss, and humanity’s overenthusiastic use of synthetic chemicals.

Australians use large amounts of pesticides to tackle creepy crawlies in their homes and gardens. But our fondness for fly spray has potentially serious impacts on urban ecosystems and public health.

We need a more sustainable way to deal with urban insect pests. Our recently published article in the Journal of Pest Science outlines some of the ways to do it.

What’s wrong with pesticides anyway?

Since becoming publicly available in the 1950s, insect sprays have been a popular way to deal with cockroaches, flies, moths, and ants around the home and backyard, and are also widely used by local councils to keep pests at bay. But what may have been effective in the past won’t necessarily work in the future, or may have unintended consequences.

Many pests, such as mosquitoes, are now becoming resistant to commonly used products. In parts of the world affected by diseases such as dengue, this jeopardises our ability to control outbreaks.




Read more:
Chemical or natural: what’s the best way to repel mozzies?


Another, perhaps wider, problem is that indiscriminate use of insecticides can kill more than just pests. Many species on which we rely for keeping our backyard gardens, bushland, wetlands and parks healthy can become collateral damage. This includes predatory species that can themselves help keep pests under control. As pest species often reproduce faster than their predators (a pattern that’s likely to be reinforced by climate change), we can get trapped in a cycle in which pest numbers bounce back higher than ever.

Many wasps are predatory and specialise in eating insects that can be pests around the home.
Manu Saunders



Read more:
Five reasons not to spray the bugs in your garden this summer


How do we do things differently?

Fortunately, there are alternatives to chemical pest control that don’t harm your household or the environment. For centuries, sustainable agriculture systems have used environmentally friendly approaches, and city-dwellers can take a leaf from their books.

Integrated pest management is one such sustainable approach. It focuses on prevention rather than treatment, and uses environmentally friendly options such as biological control (using predators to eat pests) to safeguard crops. Chemical insecticides are used only as a last resort.

There are many other farming practices that support sustainable pest control; these focus on behavioural change such as keeping areas clean, or simple physical controls such as fly mesh or netting around fruit trees.

Adopting these methods for urban pest control isn’t necessarily straightforward. There might be local regulations on particular pest control activities, or simply a lack of knowledge about urban pest ecology.

For urgent pest situations, it may be more expensive and time-consuming to set up a biological control program than to arrange the spraying of an insecticide. Insecticides take effect immediately, whereas biological control takes longer to have an effect. Prevention, the cornerstone of integrated pest management, requires careful planning before pests become a nuisance.

The goal of integrated pest management is not to eliminate insect pests entirely, but rather to reduce their numbers to the point at which they no longer cause a problem. By this logic, chemical insecticides should only be used if the economic damage caused by the pests outweighs the cost of the chemicals. If you hate the idea of a single cockroach living anywhere nearby, this might require you to adjust your mindset.

What can I do at home?

Don’t give pests opportunities. Be mindful of how we produce and dispose of waste. Flies and cockroaches thrive in our rubbish, but they can be effectively managed by ensuring that food waste is stored in insect-proof containers, recycled, or properly disposed of. Don’t leave buckets of water around the backyard, as this invites mosquitoes to breed.

Don’t open your door to pests. Seal cracks and crevices in the outside of your house, and ensure there are screens on your doors and windows.

Support the animals that control insect pests – they’ll do the hard work for you! In particular, don’t be so quick to kill spiders and wasps, because they prey on pests in your home and garden.

Spiders like this leaf curler will happily eat a range of pests, including ants, around your home.
jim-mclean/flickr



Read more:
The secret agents protecting our crops and gardens


What can we do as a community?

Urban communities can learn a lot from sustainable farming. First, there needs to be better education and support provided to the public and policy makers. Workshops run by local councils and information sessions with local gardening groups are a great way to start.

We can also work together to help debunk the popular myth that most insects are damaging or unwanted pests. Reaching for the fly spray might be easy, but remember you may end up killing friends as well as foes.The Conversation

Lizzy Lowe, Postdoctoral researcher, Macquarie University; Cameron Webb, Clinical Lecturer and Principal Hospital Scientist, University of Sydney; Manu Saunders, Research fellow, University of New England, and Tanya Latty, Senior Lecturer, School of Life and Environmental Sciences, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Five reasons not to spray the bugs in your garden this summer



File 20171103 26444 1qfv62d.jpg?ixlib=rb 1.1

play4smee/Flickr, CC BY-NC

Lizzy Lowe, Macquarie University; Cameron Webb, University of Sydney, and Kate Umbers, Western Sydney University

The weather is getting warmer, and gardens are coming alive with bees, flies, butterflies, dragonflies, praying mantises, beetles, millipedes, centipedes, and spiders.

For some of us it is exciting to see these strange and wonderful creatures return. For others, it’s a sign to contact the local pest control company or go to the supermarket to stock up on sprays.

But while some bugs do us very few favours – like mozzies, snails and cockroaches – killing all insects and bugs isn’t always necessary or effective. It can also damage ecosystems and our own health.


Read more: The hidden secrets of insect poop


There are times when insecticides are needed (especially when pest populations are surging or the risk of disease is high) but you don’t have to reach for the spray every time. Here are five good reasons to avoid pesticides wherever possible, and live and let live.

1. Encourage the bees and butterflies, enjoy more fruits and flowers

Hover fly.
dakluza/flickr

Flowers and fruits are the focal points of even the smallest gardens, and many of our favourites rely on visits from insect pollinators. We all know about the benefits of European honey bees (Apis mellifera), but how about our “home grown” pollinators – our native bees, hover flies, beetles, moths and butterflies. All these species contribute to the pollination of our native plants and fruits and veggies.


Read more: The common herb that could bring bees buzzing to your garden


You can encourage these helpful pollinators by growing plants that flower at different times of the year (especially natives) and looking into sugar-water feeders or insect hotels.

2. Delight your decomposers, they’re like mini bulldozers

Slaters improve your soil quality.
Alan Kwok

To break down leaf litter and other organic waste you need decomposers. Worms, beetles and slaters will munch through decaying vegetation, releasing nutrients into the soil that can be used by plants.

The problem is that urban soils are frequently disturbed and can contain high levels of heavy metals that affects decomposer communities. If there are fewer “bugs” in the soil, decomposition is slower – so we need to conserve our underground allies.

You can help them out with compost heaps and worm farms that can be dug into the ground. It’s also good to keep some areas of your lawn un-mowed, and to create areas of leaf litter. Keeping your garden well-watered will also help your underground ecosystems, but be mindful of water restrictions and encouraging mosquitoes.

3. An army of beneficial bugs can eat your pests

Mantises and dragonflies are just some of the hundreds of fascinating and beautiful bugs we are lucky to see around our homes. Many of these wonderful creatures are predators of mozzies, house flies and cockroaches, yet people are using broad-spectrum insecticides which kill these beneficial bugs alongside the pests.

It may sound counterproductive to stop using pesticides in order to control pests around the home, but that’s exactly what organic farmers do. By reducing pesticides you allow populations of natural enemies to thrive.


Read more: Even ‘environmentally protective’ levels of pesticide devastate insect biodiversity


Many farmers grow specific plants to encourage beneficial insects, which has been shown to reduce the damage to their crops.

This form of pest control in growing in popularity because spraying can result in insecticide resistance. Fortunately, it’s easy to encourage these bugs: they go where their prey is. If you have a good range of insects in your yard, these helpful predators are probably also present.

Jumping spiders are great at eating flies and other pests.
Craig Franke

4. Your garden will support more wildlife, both big and small

Spraying with broad-spectrum pesticides will kill off more than just insects and spiders – you’re also going after the animals that eat them. The more insects are around, the more birds, mammals, reptiles and frogs will thrive in your backyard.


Read more: Four unusual Australian animals to spot in your garden before summer is out


Baiting for snails, for example, will deter the blue-tongue lizards that eat them, so cage your vegetables to protect them instead. Keeping your garden well-watered, and including waterbaths, will also encourage a balanced ecosystem (but change the waterbaths regularly).

5. You and your family be happier and healthier

Engaging with nature increases well-being and stimulates learning in children. Insects are a fantastic way to engage with nature, and where better to do this than in your own back yard! Observing and experimenting on insects is a wonderful teaching tool for everything from life cycles to the scientific method. It will also teach your kids to value nature and live sustainably.

It’s also a hard truth that domestic pesticides present a significant risk of poisoning, especially for small children.

In reality, the risk of exposing your children to the pesticides far outweighs the nuisance of having a few bugs around. Instead, integrated pest management, which combines non-chemical techniques like cleaning of food residues, removal of potential nutrients, and sealing cracks and crevices, is safer for your family and your garden ecosystems.

Think globally, act locally

Your backyard has a surprising impact on the broader health of your neighbourhood, and gardens can make significant contributions to local biodiversity. Insects are an important part of ecosystem conservation, and encouraging them will improve the health of your local environment (and probably your health and well-being too).


Read more: Conservation efforts must include small animals. After all, they run the world


The ConversationIn the end, insects and spiders are not out to get you. For the sake of our kids and our environment, you should give them a chance.

Lizzy Lowe, Postdoctoral researcher, Macquarie University; Cameron Webb, Clinical Lecturer and Principal Hospital Scientist, University of Sydney, and Kate Umbers, Lecturer in Zoology, Western Sydney University

This article was originally published on The Conversation. Read the original article.

Mozzies are evolving to beat insecticides – except in Australia



File 20170713 9462 16t5ncj
Mosquitoes are the main vectors for dengue and zika. Insecticides are our best weapon against them.
Anja Jonsson/Flickr

Ary Hoffmann, University of Melbourne; Nancy Margaret Endersby-Harshman, University of Melbourne, and Scott Ritchie, James Cook University

Chemical pesticides have been used for many years to control insect populations and remain the most important method of managing diseases carried by pests, including mosquitoes. However, insects have fought back by evolving resistance to many pesticides. There are now thousands of instances of evolved resistance, which make some chemical classes completely ineffective.

The Aedes mosquito, largely responsible for the spread of viruses like dengue and zika, has globally developed resistance to commonly used chemicals, including pyrethroids. Pyrethroids are the most used insecticides in the world, which includes the control of dengue outbreaks and quarantine breaches at air and sea ports.

In Asia and the Americas, pyrethroid resistance in Aedes mosquitoes is now widespread. In Australia, our mosquitoes have not developed these defences and pyrethroids are still very effective.

The difference lies in our stringent and careful protocols for chemical use. As the global community fights zika and other mosquito-borne diseases, there are lessons to be learned from Australia’s success.

Developing resistance

Mosquitoes usually become resistant to pyrethroids through the mutation of a sodium channel gene that controls the movement of ions across cell membranes. Mutations in a single gene are enough to make mosquitoes almost completely resistant to the level of pyrethroids used in insecticides.

The mutations first arises in a population by chance, and are rare. However, they rapidly spread as resistant females breed. The more times a mosquito population is exposed to the same chemical, the more the natural selection process favours their impervious offspring.

Eventually, when many individuals in a population carry the resistance mutation, the chemical becomes ineffective. This can happen where insecticide “fogging” is common practice. Overseas, fogging is sometimes undertaken across entire neighbourhoods, several times a month, despite concerns about its effectiveness as well as its environmental and health impacts.

A pest exterminator carries out insecticide fogging in an apartment block in Singapore.
EPA, Wallace Woon/AAP

Once resistance develops, it can spread to non-resistant mosquito populations in other areas. Pest species, including mosquitoes, are often highly mobile because they fly or are carried passively (in vehicles, ships and planes) at any stage of their life cycle. Their mobility means mutations spread quickly, crossing borders and possibly seas.

We can still control Australian mosquitoes

Despite this, Australian populations of Aedes mosquitoes remain susceptible to pyrethroids. Aedes aegypti (the yellow fever mosquito) is the main disease-carrying mosquito in Australia. Its population is restricted to urban areas of northern Queensland, where dengue can occur.

Recent research found that all Australian populations of this species are still vulnerable to pyrethroids. None of the hundreds of mosquitoes tested had any mutations in the sodium channel gene, despite the high incidence of such mutations in mosquito populations of South-East Asia.

A female Aedes aegypti mosquito during a feed.
James Gathany, CDC Prof Frank Hadley Collins/Wikimedia

We believe these mosquitoes remain vulnerable to pyrethroids because in Australia pressure to select for resistance has been low.

Australia does not carry out routine fogging. If dengue is detected in an area, pyrethoids are used in highly regimented and limited fashion. Spraying is restricted to the insides of premises within selected house blocks, and then only for a short period.

Importantly, water-filled artificial containers, which can serve as a habitat for larvae, are treated with insect growth regulators, which do not select for the pyrethroid resistance mutations.

Exporting resistance

With chemical resistance growing around the world, it is more urgent than ever that we co-ordinate action to control and reduce risk of resistance. Unfortunately, no global guidelines exist to minimise the evolution of resistance in mosquitoes.

Adopting pesticide resistance management strategies has proven to be effective against other pests – for example, the corn earworm (Helicoverpa armigera). Guidelines include rotating different class of pesticides to deny pests the chance to develop resistance, and investing in non-chemical options such as natural predators of target pests.

Resistance management strategies are particularly critical for new pesticides that have different modes of attack, such as preventing juvenile insects from moulting, or attacking various chemical receptors.

The ConversationTo prolong the effectiveness of pesticides, we must develop these strategies before resistance begins to develop. North Queensland may be an example to the rest of the world on the best path forward.

Ary Hoffmann, Professor, School of BioSciences and Bio21 Institute, University of Melbourne; Nancy Margaret Endersby-Harshman, Research fellow, University of Melbourne, and Scott Ritchie, Professorial Research Fellow, James Cook University

This article was originally published on The Conversation. Read the original article.