5 Mosquito-Borne Diseases in Australia: Symptoms, Risks & Prevention
, by Tatianna Gerard, 14 min reading time
Mosquitoes are often seen as nothing more than irritating pests, but in reality, they are capable of transmitting some of the most serious diseases in the world. In Australia, mosquito-borne diseases pose a significant public health risk, especially in certain regions and during specific seasons.
In this blog, we will explore the top 5 diseases caused by mosquitoes in Australia. We’ll discuss how these diseases are transmitted, what symptoms to watch out for, and the best ways to prevent infection.
1. Ross River Virus
Ross River virus is one of the most common mosquito-borne diseases in Australia. It is named after the Ross River in Queensland, where the virus was first identified.
Transmission:
Ross River virus is spread by several species of mosquitoes, particularly those found in coastal regions and inland waterways. The most common vectors include Aedes vigilax, a saltmarsh mosquito, and Culex annulirostris, a freshwater mosquito. These mosquitoes are often found in habitats such as wetlands, marshes, and areas with standing water. The mosquitoes become infected after biting an animal, typically a kangaroo or wallaby, that carries the virus.
Symptoms:
- Joint pain
- Swelling of joints
- Fatigue
- Fever
- Rash
Symptoms of Ross River virus can be quite debilitating and may last for weeks or even months, impacting a person’s ability to perform daily activities.
Severe symptoms requiring immediate medical attention:
- Severe joint pain that limits movement
- Persistent or high fever that does not respond to over-the-counter medications
- Severe fatigue that interferes with daily activities
- Symptoms lasting more than six months
2. Barmah Forest Virus
Barmah Forest virus is another common mosquito-borne illness in Australia. It is similar to Ross River virus but is generally considered to be milder.
Transmission:
This virus is transmitted by mosquitoes found in forested and rural areas, particularly during the warmer months. Aedes vigilax and Culex annulirostris are the primary vectors for Barmah Forest virus, much like Ross River virus. These mosquitoes thrive in areas with abundant vegetation and standing water. The mosquitoes become infected after feeding on a host, such as a marsupial, that carries the virus.
Symptoms:
- Joint pain
- Rash
- Fever
- Fatigue
Although the symptoms of Barmah Forest virus are usually milder, they can still last for several weeks, causing discomfort and fatigue.
Severe symptoms requiring immediate medical attention:
- Severe joint pain or swelling that does not improve
- Persistent rash that spreads or worsens
- High fever that does not subside with treatment
- Extreme fatigue that impacts quality of life
3. Dengue Fever
Dengue fever is a more serious mosquito-borne disease that has seen outbreaks in northern Australia, particularly in tropical regions like northern Queensland.
Transmission:
Dengue fever is spread by two main types of mosquitoes: the Dengue mosquito (Aedes aegypti) and the Asian Tiger mosquito (Aedes albopictus). These mosquitoes are commonly found in regions like Asia, Africa, and South America. In Australia, most areas are free from these mosquitoes; however, they are present in Central and Far North Queensland, as well as the Torres Strait. Outbreaks in these areas typically occur when an individual infected overseas returns to Australia, and a local mosquito bites them, subsequently spreading the virus to others in the community.
Symptoms:
- High fever
- Severe headache
- Pain behind the eyes
- Joint and muscle pain
- Rash
- Mild bleeding (e.g., gums or nosebleeds)
Dengue fever can range from mild to severe. Severe cases may lead to dengue haemorrhagic fever, which is a potentially life-threatening condition.
Severe symptoms requiring immediate medical attention:
- Severe abdominal pain or persistent vomiting
- Bleeding from the nose, gums, or under the skin
- Rapid breathing or difficulty breathing
- Severe drop in blood pressure (shock)
- Severe headache with vomiting or confusion
4. Murray Valley Encephalitis
Murray Valley encephalitis is a rare but potentially deadly mosquito-borne disease found in Australia. It primarily affects rural and regional areas, particularly in the Murray-Darling basin.
Transmission:
The disease is transmitted by Culex annulirostris, a common mosquito species in Australia, particularly in rural regions with ample standing water, such as wetlands and floodplains. These mosquitoes become infected after feeding on waterbirds, which are the primary carriers of the virus. It’s important to note that the virus is not passed to humans through direct contact with birds or other animals; it is only spread through mosquito bites.
Most cases of Murray Valley encephalitis occur during or shortly after the wet season when mosquito populations are at their peak. Recently, traces of the virus have also been detected in chickens in the central west of the state, further highlighting the importance of mosquito control and personal protection in affected areas.
Symptoms:
- Initial flu-like symptoms (fever, headache, nausea)
- Muscle aches
- Confusion
While many people infected with the virus do not develop symptoms, those who do may experience severe neurological issues that can be life-threatening.
Severe symptoms requiring immediate medical attention:
- Severe headache that does not go away
- Neck stiffness or sensitivity to light
- Confusion, disorientation, or changes in personality
- Seizures or convulsions (especially in younger children)
- Loss of consciousness or coma
5. Japanese Encephalitis
Japanese encephalitis is another serious mosquito-borne disease that has been detected in parts of Australia, particularly in northern regions and areas associated with pig farming, as pigs can act as amplifying hosts.
Transmission:
Japanese encephalitis is transmitted by Culex tritaeniorhynchus and Culex annulirostris mosquitoes. These mosquitoes are typically found in rural areas with large bodies of water, such as rice paddies, swamps, and areas with significant pig farming operations. Pigs serve as important hosts for the virus, amplifying it and increasing the risk of transmission to humans.
Symptoms:
- Mild cases may have no symptoms
- High fever
- Headache
- Vomiting
- Confusion
- Seizures
In severe cases, Japanese encephalitis can lead to brain inflammation, which may result in life-threatening complications. According to the World Health Organization (WHO), the fatality rate for those who develop symptoms can be as high as 30%. Among those who survive, approximately 20-30% are left with long-term complications. These may include permanent cognitive, behavioural, or neurological issues, such as seizures, loss of hearing or vision, difficulties with speech, language, memory, and communication, or weakness in the limbs.
Severe symptoms requiring immediate medical attention:
- Severe headache with vomiting or vision changes
- Neck stiffness or sensitivity to light
- Confusion or disorientation
- Seizures or convulsions
- Sudden onset of paralysis or weakness
Recent developments: Detection in Moree, NSW
In a concerning development, Japanese encephalitis virus (JEV) has recently been detected in mosquitoes around Moree, located in north-western New South Wales. This marks the first time the virus has been identified in the area, raising alarms about its spread. The recent combination of heavy rainfall and soaring temperatures across the region has created ideal breeding conditions for mosquitoes, significantly increasing the risk of large-scale JEV infections.
While JEV is not transmissible from person to person, it can be transmitted through the bite of an infected mosquito. The virus can also spread through animals such as waterbirds and pigs, which act as reservoirs for the disease.
Why is this alarming?
Mosquito-borne diseases thrive in warm, wet climates, and the current environmental conditions in north-west NSW are fuelling mosquito populations. This has heightened the risk of exposure to not only JEV but other mosquito-borne diseases as well, underscoring the importance of personal protection and mosquito control measures in the affected areas.
Japanese encephalitis vaccination
Vaccination is one of the most effective ways to protect against Japanese encephalitis virus (JEV), especially for individuals in high-risk areas or those who may be exposed due to their work or lifestyle. There are two safe and effective vaccines currently available in Australia:
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Imojev: A single-dose vaccine suitable for people aged 9 months and older. It provides effective protection and is ideal for individuals looking for a convenient vaccination schedule.
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JEspect/Ixiaro: This vaccine requires two doses and is recommended for infants and children aged 2 months and older. It is also safe for use in individuals with compromised immune systems and pregnant women.
Who is eligible for a free Japanese encephalitis vaccination?
In New South Wales, free Japanese encephalitis virus (JEV) vaccinations are available to individuals aged 2 months and older who live or routinely work in specific Local Government Areas (LGAs), including Moree. To qualify, individuals must also meet at least one of the following criteria:
- Spend significant time outdoors, putting them at risk of mosquito bites.
- Experience homelessness.
- Reside in settings with minimal mosquito protection, such as tents, caravans, or dwellings without insect screens.
- Participate in outdoor flood recovery efforts, including professional or volunteer clean-up activities.
For a complete list of eligible LGAs, visit the NSW Health website.
Additionally, free vaccinations are recommended for individuals across any part of NSW who work, live, or visit high-risk areas or engage in specific roles, such as:
Pig-related occupations:
- Workers and families (including children aged 2 months or older) living on or near piggeries.
- Pig transport workers.
- Veterinarians (including students and nurses) and others caring for pigs.
- Employees in pork abattoirs or rendering plants.
Mosquito surveillance or control workers:
- Environmental health officers, entomologists, or others involved in mosquito surveillance or control measures.
- Individuals managing vertebrate mosquito-borne disease surveillance systems, such as sentinel animal programs.
Laboratory workers:
- Researchers and diagnostic lab personnel who may handle JEV cultures or work with infected mosquitoes.
While vaccines are available in NSW, there is currently a limited supply of Japanese encephalitis vaccines due to global ordering constraints. If you are eligible and planning to receive the vaccine, it is important to inform your healthcare provider that it is for Japanese encephalitis. They may require a few days' notice to order the vaccine, so advanced planning is essential.
If you fall into any of these categories, contact your healthcare provider or local health authority to check your eligibility and arrange vaccination.
Prevention and protection tips
Mosquito-borne diseases pose a serious health risk, but there are several steps you can take to protect yourself.
1. Use insect repellents
Using insect repellents is one of the most effective ways to prevent mosquito bites. Products containing DEET or picaridin are usually recommended for their efficacy.
If you prefer natural alternatives, consider using Good Riddance insect repellents. Developed in the Northern Territory, these laboratory-proven repellents do not contain DEET or picaridin. Instead, they are formulated with essential oils such as lemongrass, lemon tea tree oil, and lavender, all of which effectively repel mosquitoes. The strong, fresh scent of lemongrass and lemon tea tree oil disrupts the mosquitoes' ability to detect the carbon dioxide and lactic acid we emit, which are the primary signals they use to locate us. Lavender oil adds a soothing fragrance while also serving as a natural deterrent due to its ability to mask the human scent that attracts mosquitoes.
Check out our Good Riddance range:
2. Wear protective clothing
Cover up with long sleeves, trousers, and light-coloured clothing to make it harder for mosquitoes to bite. Mosquitoes are less likely to penetrate thicker fabrics, and light colours are less attractive to these insects.
3. Eliminate standing water
Mosquitoes breed in stagnant water, so it’s essential to ensure there are no standing water sources around your home. Regularly empty containers like birdbaths, plant saucers, and buckets to reduce breeding sites.
4. Use mosquito nets and screens
Protect your living spaces by installing screens on windows and using mosquito nets while sleeping, particularly in areas where mosquito-borne diseases are prevalent. This physical barrier helps keep mosquitoes out of your home and away from your sleeping area.
Conclusion
Mosquito-borne diseases are a significant public health concern in Australia, particularly in certain regions. By understanding the symptoms and transmission methods of these diseases, you can take proactive steps to protect yourself and your community. Prevention is key, and by staying informed and prepared, you can reduce your risk of contracting these potentially serious illnesses.