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Find answers to some of the most commonly asked questions about the World Mosquito Program.

1What does the World Mosquito Program do?

The World Mosquito Program is a not-for-profit initiative that works to protect the global community from mosquito-borne diseases. We use safe and natural bacteria called Wolbachia to reduce the ability of mosquitoes to transmit viruses such as dengue, Zika, chikungunya and yellow fever.

We are committed to strengthening the capacity of local communities around the world to reduce the threat of mosquito-borne diseases. We are expanding our method for low-cost, large-scale application across urban areas in countries affected by mosquito-borne diseases. We are collaborating with local communities, governments and health agencies to implement our self-sustaining Wolbachia method.

Learn more about our work here.

2How does the World Mosquito Program's Wolbachia method work?

Our Wolbachia method works by introducing Wolbachia into Aedes aegypti mosquitoes, the primary vector of the dengue, Zika, chikungunya and yellow fever viruses. We release Wolbachia-carrying mosquitoes in areas where these mosquito-borne viruses are endemic. Once our Wolbachia mosquitoes are released, they breed with wild mosquitoes. Over time, the percentage of mosquitoes carrying Wolbachia grows until it remains high without the need for further releases.

Learn more about our Wolbachia method here.

3Where is the World Mosquito Program working?

The World Mosquito Program is currently operating in 12 countries around the world – Australia, Brazil, Colombia, Indonesia, Sri Lanka, India, Vietnam, Kiribati, Fiji, Vanuatu, New Caledonia and Mexico.

We are expanding our method for low-cost, large-scale application across urban areas in countries affected by mosquito-borne diseases. We are collaborating with local communities, governments and health agencies to implement our self-sustaining, long-term solution.

Learn more about our projects here.

4Does the World Mosquito Program's approach involve genetic modification?

Our method does not involve the use of genetically modified organisms (GMO). GMO technology is defined as the use of particular procedures to alter the natural composition of an animal or plant’s DNA. Our method is not genetic modification, as the genetic material of the mosquito has not been altered. Neither the Aedes aegypti mosquitoes nor the Wolbachia have been genetically modified in the lab and the strain of Wolbachia we are using is naturally occurring.

Compare our method to others here.

5On which diseases does the World Mosquito Program's Wolbachia method have an effect?

The World Mosquito Program's Wolbachia method has been proven to reduce transmission of several viruses transmitted by the Aedes aegypti mosquito, including dengue, Zika, chikungunya, Mayaro and yellow fever. It is also predicted to have potential impacts on diseases like Japanese Encephalitis and is known to reduce mosquito infection with human parasites like malaria and filarial nematodes, however these diseases are not currently our primary focus.

For further information, read our latest research studies here.

6Can you provide some background on each of the diseases the World Mosquito Program's Wolbachia method works to prevent?

DengueZikachikungunya and yellow fever are human viruses which are transmitted primarily by the mosquito Aedes aegypti, which is commonly found around homes and workplaces. The transmission cycle for the dengue, Zika and chikungunya viruses is human → mosquito → human, while the transmission cycle for yellow fever can also include non-human primates, such as monkeys. When mosquitoes carry Wolbachia, their ability to transmit these viruses is significantly reduced.

Dengue

Dengue fever is ranked by the World Health Organization as the most critical mosquito-borne viral disease in the world – and the most rapidly expanding – with a 30-fold increase in global incidence over the past 50 years. More than 40 per cent of the world’s population, in more than 140 countries are at risk of dengue infection. The most significant dengue epidemics in recent years have occurred in Southeast Asia, the Americas and the Western Pacific. Each year, an estimated 390 million dengue infections occur around the world. Of these, 500,000 cases develop into dengue haemorrhagic fever, a more severe form of the disease, which results in up to 25,000 deaths annually worldwide.

Read more about dengue here

Zika

On 1 February 2016, the World Health Organization declared Zika virus disease a Public Health Emergency of International Concern. Zika has continued to spread geographically where Aedes aegypti mosquitoes are present, with 84 countries reporting infections. Since 2015, more than 500,000 suspected cases of Zika have been reported, with 3,521 recorded cases of congenital brain abnormalities associated with Zika. There is no vaccine or treatment for Zika virus, other than rest and treating fever with common medicines.

Read more about Zika here

Chikungunya

First identified in an outbreak in Tanzania in 1952, chikungunya is a mosquito-borne disease transmitted between humans by the Aedes aegypti mosquito. Chikungunya’s name is derived from a word in the Kimakonde language, meaning ‘to become contorted’, as the virus causes debilitating joint pain that induces a stooped appearance. Chikungunya is most prevalent in Asia, Africa and India. However, in 2015, there was a large outbreak across the Americas, with over a million suspected cases of chikungunya recorded in the Caribbean Islands, Latin America, and the United States of America. More than 190 deaths were also attributed to this disease during the same period.

Read more about chikungunya here.

Yellow fever

Yellow fever is an acute viral haemorrhagic disease transmitted by infected mosquitoes. The virus is endemic in 47 countries across Africa and Latin America. According to the World Health Organization and Pan American Health Organization, yellow fever is estimated to infect 200,000 people, with an estimated 30,000 deaths annually. Thirteen countries in the Americas are considered to be at highest risk for yellow fever outbreaks, including Brazil and Colombia, where we work. While the urban transmission of yellow fever by Aedes aegypti has not been reported in Brazil since 1942, the risk of re-urbanisation of the disease remains, as these mosquitoes are found in most tropical and subtropical cities in the world and have been the main mosquito responsible for epidemic transmission of yellow fever in the past.

Read more about yellow fever here.

7How does the World Mosquito Program's approach compare to other solutions in development?

There are several different approaches to reducing mosquito-borne diseases that are at various stages of development around the world. One of these is a dengue vaccine, which is being explored by a number of research groups and organisations. Other methods that are under development include new insecticides and new methods of applying existing insecticides. Other groups are also exploring ways to genetically modify mosquitoes to control their breeding. Finally, some groups are attempting to use Wolbachia, not the way we use it, but as a tool to facilitate mosquito suppression. 

Our Wolbachia approach is self-sustaining and predicted to have lasting, major reductions in arboviral disease incidence and in most urban settings is expected to be cost-saving for countries to implement. In contrast, suppression approaches that utilise Wolbachia require significant infrastructure to rear large numbers of male mosquitoes and human resources to distribute them in the community – this must be done continuously, otherwise the wild mosquito population rebounds. There is no evidence yet that suppression approaches can reduce mosquito populations at a large scale (ie. the level of a city), or that this approach can reduce disease incidence. Our approach, however, can be scaled to the level of large towns and cities and we have generated evidence directly on the impact on disease in human populations.

Our approach is a natural method to reduce the transmission of mosquito-borne diseases, which we hope will reduce our reliance on insecticides. Our method does not involve genetic modification, as the genetic material of the mosquito has not been altered. Our approach is particularly effective at controlling mosquito-borne diseases in large urban areas where conventional approaches – such as spraying insecticides – are often ineffective and expensive.

The unique advantage of our Wolbachia method is that in addition to helping to protect communities from mosquito-borne diseases like dengue, Zika, chikungunya, Mayaro and yellow fever, we are not posing a risk to natural ecosystems. Long-term monitoring shows that our natural Wolbachia method is self-sustaining and will maintain itself indefinitely. Our first releases were undertaken in 2011 in Australia and, as predicted, the Wolbachia has maintained itself in those sites ever since. 

Learn more about how our method compares here.

8You say the World Mosquito Program's Wolbachia method will be more economical and sustainable than other methods. Why is that?

The World Mosquito Program is implementing a self-sustaining, cost-effective form of vector control, without needing to continually suppress the mosquito population. In contrast to insecticide-based programs, or the use of Wolbachia for population suppression, our method has the potential to offer sustained protection from disease regardless of the number of mosquitoes present in the environment.

We aren’t trying to reduce the overall number of mosquitoes, instead we aim to boost the number of Wolbachia-carrying mosquitoes to reduce their ability to transmit diseases. We release a small number of male and female mosquitoes with Wolbachia over a number of weeks and these mosquitoes then mate with the wild mosquito population. The bacteria are passed from generation to generation, and over time, the percentage of mosquitoes carrying Wolbachia grows until it remains high without need for further releases. Mosquitoes with Wolbachia are less able to transmit viruses to people, so the risk of outbreaks in those areas is greatly reduced or eliminated.

Our work has shown that Wolbachia can sustain itself in mosquito populations without continual reapplication, making this a long-term, cost-effective and self-sustaining approach. We are currently adapting our approach for use in large, urban environments, and targeting a cost of US$1 per person protected.

Learn more about our sustainability model here.

9Will the World Mosquito Program's Wolbachia method be effective in the long-term?

It’s very difficult to predict how long the Wolbachia method of control will be effective. We could imagine that over time the method might become less effective but we have no way to predict how quickly that might happen. Experience has shown that most control measures – whether they be insecticides or biological control – can become less effective over time due to the evolution of resistance. Currently, we have not detected any signs of resistance in any of our release sites. Our current work suggests that we can expect to have effective control with this method for at least decades and potentially much longer. 

The possibility of effective but transient control should not be seen as a negative attribute of this technology. Many control measures become less effective over time. For example, many insect pests have shown increasing resistance to chemical insecticides. Yet, these tools have been incredibly valuable in saving human lives from major diseases such as dengue and malaria.

Learn more about our sustainability model here.

10Who is funding the World Mosquito Program?

The World Mosquito Program is an international, non-profit initiative led from Monash University, Australia. We have developed strong relationships with governments, research institutes and philanthropic partners around the world. 

See our full list of financial supporters here.

Aedes aegypti mosquitoes

Aedes aegypti mosquitoes spread viruses like dengue, Zika, chikungunya and yellow fever. Learn more about this mosquito and its environment.

1What kind of mosquito transmits dengue, Zika, chikungunya and yellow fever?

Aedes aegypti is the primary vector of the dengueZikachikungunya and yellow fever viruses. The Aedes aegypti mosquito looks like many other mosquitoes and is difficult to identify without the use of a microscope. As a rule, if they are dark brown to black in colour, found indoors and bite during the day, it is likely that they are Aedes aegypti mosquitoes.

Unlike other types of mosquitoes, the Aedes aegypti mosquito has adapted to live and breed in urban areas in close proximity to humans. The mosquito breeds in artificial containers (e.g. old tyres and pot-plant trays) that collect water and bites humans almost exclusively to get protein from the blood for mosquito egg development.

2What is a mosquito's role in the environment?

There are many different types or species of mosquitoes that live naturally in the environment. Some mosquitoes do not live in close association with humans like Aedes aegypti and prefer to live in natural wetland environments. In these natural environments, the aquatic larval stage can be an important food source for animals such as fish. The adults of these mosquitoes can bite humans but more typically will bite other animals, birds and even frogs or lizards.

Aedes aegypti mosquitoes are highly adapted to humans and live where humans live. In this way they are similar to domestic cockroaches. Their ecology overlaps with human ecology and they prefer to live and breed where humans live. They don’t live in forests or wetlands unless humans live there. As a result they have little contact or importance to natural ecosystems. 

3How long does an Aedes aegypti mosquito live – and how far does it fly?

The adult lifespan of the Aedes aegypti mosquito can range from two weeks to a month depending on environmental conditions. The average Aedes aegypti mosquito will fly relatively short distances and travel no more than 150 metres in its lifetime. However, its eggs can withstand drying and can become highly mobile, allowing them to be carried around the world attached to human belongings.

Wolbachia bacteria

Wolbachia bacteria can have a powerful effect on mosquitoes. Learn more about Wolbachia and how it can help prevent diseases.

1What is Wolbachia?

Wolbachia are safe, natural bacteria present in up to 60% of species, including some mosquitoes. However, Wolbachia is not usually found in the Aedes aegypti mosquito, the primary species responsible for transmitting viruses such as dengue, Zika, chikungunya and epidemic yellow fever.

For many years, scientists have been studying Wolbachia, looking for ways to use it to potentially control the mosquitoes that transmit human diseases. The World Mosquito Program’s research has shown that when introduced into the Aedes aegypti mosquito, Wolbachia can help to reduce transmission of the dengueZika, chikungunya, Mayoro and yellow fever viruses to people.

Learn more about Wolbachia here.

2How does Wolbachia work?

Current evidence indicates that Wolbachia works in two ways within a mosquito. The first way is to boost the natural immune system of the mosquito to make it harder for the mosquito to support the dengueZikachikungunya, Mayaro or yellow fever infection. If the mosquito can’t get infected, then it can’t transmit these viruses to people.

The second way Wolbachia works is by competing against viruses for key molecules like cholesterol. Both the viruses and Wolbachia need cholesterol to survive inside the mosquito. When Wolbachia is present, it consumes these molecules and makes it harder for the viruses to grow. If it’s harder for the viruses to grow, then it’s harder for them to be transmitted.

Learn more about Wolbachia here.

3How does the World Mosquito Program use Wolbachia?

We maintain colonies of Wolbachia carrying Aedes aegypti mosquitoes in our laboratories. We take relatively small numbers of these laboratory-grown mosquitoes and release them into a target location, where they will breed and pass the Wolbachia into the wild population. The Wolbachia will then spread and typically maintain itself in more than 90% of the wild mosquitoes indefinitely.

These mosquitoes have a reduced ability to transmit viruses to people, decreasing the risk of dengue, Zika, chikungunya, Mayaro and yellow fever outbreaks.

Our Wolbachia method can protect communities from mosquito-borne diseases without posing risk to natural ecosystems. Unlike most other initiatives, our method is natural and self-sustaining.

Learn more about Wolbachia here.

4Is Wolbachia safe?

Wolbachia is safe for humans, animals and the environment. Our Wolbachia method helps to protect communities from mosquito-borne diseases like dengueZika, chikungunya, Mayaro and yellow fever and does so without risk to natural ecosystems or human health.

Following years of laboratory and field-based research, our findings have been subjected to rigorous independent assessments. The results concluded that there is negligible risk associated with the release of Wolbachia carrying mosquitoes and that Wolbachia is safe for people, animals and the environment. This is the lowest-possible risk rating.

Learn more about Wolbachia here.

5Will the bite of a mosquito with Wolbachia hurt more than a normal bite?

No. People who are bitten by an Aedes aegypti mosquito containing Wolbachia will not notice any difference or be adversely affected in any way. 

6Is Wolbachia harmful to the environment?

No. Wolbachia are naturally occurring bacteria that are safe for humans, animals and the environment.

For more information, download the CSIRO's Risk Assessment Report.

7Do other animals carry Wolbachia?

Wolbachia is common among arthropods (including insects, spiders and other small animals with no backbone). Up to 60 per cent of species naturally carry Wolbachia, including butterflies, dragonflies, moths and some mosquito species, but not the primary species of mosquito involved in the transmission of dengueZika, chikungunya and yellow fever.

Wolbachia is also found in certain types of roundworms – known as nematodes – but this is very different to the insect inhabiting Wolbachia that we work with. Wolbachia is not found in any larger animals such as mammals, reptiles, birds and fish.

8What type of Wolbachia does the World Mosquito Program work with?

Wolbachia refers to a whole genus of bacteria, of which there are many different types and strains. We’ve examined several strains of insect Wolbachia, and the most effective strain we’ve found is the one that we are currently using in the field, called wMel.

Our researchers have also been examining different strains of Wolbachia including wMelCS, wAlbB, wRi and wPip. While we have had great success in establishing our current Wolbachia strain in wild mosquito populations, testing additional strains could lead to better optimisation of the method in different locations as well as provide a strategy to account for the possible evolution of resistance.

9How does Wolbachia establish and maintain itself in mosquito populations?

Wolbachia can only be transmitted from parent to offspring inside the female’s egg. When a male mosquito that carries Wolbachia mates with a female without the bacteria then that female’s eggs don’t hatch.

Wolbachia-infected female mosquitoes, however, produce normal numbers of offspring – which carry Wolbachia. Initially, this reproductive effect will be very small as there will be few Wolbachia-carrying mosquitoes in the overall population, but over successive generations the proportion of males and female mosquitoes with Wolbachia in a mosquito population will increase.

This process is called cytoplasmic incompatibility and is important for Wolbachia establishment and maintenance in mosquito populations.

Watch the video on How It Works for more information on cytoplasmic incompatibility.

10Is Wolbachia directly affected by the temperature of its environment?

Wolbachia and mosquitoes can both be affected by high temperatures. At high temperatures, the density of Wolbachia decreases in the mosquito (larvae and adults) and maternal transmission of Wolbachia is reduced. Importantly, however, the evidence of successful Wolbachia establishment in Indonesia, northern Australia, Brazil and Colombia indicates that temperature is not typically a problem for establishing Wolbachia.