We explore how climate change could affect British mosquitoes and the diseases they spread, and discuss pioneering LSHTM studies with 'princess mosquitoes'
Mosquitoes are the vectors for a number of potentially deadly diseases including malaria and viruses such as dengue. Although the risk of disease from British mosquitoes is low, a recent UKHSA report warned that the risk of vector-borne diseases is increasing as our climate changes. It's therefore crucial to monitor mosquitoes for any changes or risks to human health as the climate changes.
Researchers at LSHTM have set up the first colony of a native British mosquito species, to study them in detail and inform efforts to tackle vector-borne disease threats.
In the second instalment of our two-part series on mosquitoes in the UK, Dr Mojca Kristan, Assistant Professor at LSHTM, introduces the 'princess' Aedes vexans mosquito colony and explains why researching these high-maintenance insects is so important.
With climate change, will we see more mosquitoes in the UK?
If the climate trends such as mild and wet winters and warmer summers continue, we will probably see more native British mosquitoes. It is possible that other invasive mosquito species will also move into the UK.
Could we get mosquito-borne diseases in the UK?
Potentially, yes. In 2025, the UKHSA reported that fragments of West Nile virus were detected in Aedes vexans mosquitoes in Nottinghamshire in 2023. Continued surveillance in mosquitoes and birds from across England shows there is no evidence that West Nile virus is circulating, and there have been no locally acquired bird, horse or human infections reported. We have started a research project to investigate the potential implications of West Nile virus moving into British Aedes vexans mosquitoes, and how it may survive and start circulating in this environment.
Invasive species capable of transmitting other viruses such as dengue, chikungunya and Zika, including Aedes albopictus (Asian tiger mosquito) and Aedes aegypti (Egyptian mosquito), are currently not present in the UK, though eggs of Aedes albopictus have been detected in the UK. Some of these viruses, such as dengue and chikungunya, are already present in Europe (especially the Mediterranean). The UK climate is not yet conducive for the establishment of these viruses or vectors, but modelling studies show that by the 2060s, the climate in London and surrounding areas will likely support endemic (sustained local) transmission of dengue.
Why don't we have malaria in the UK, and could it come back in the future?
Malaria is only transmitted by Anopheles mosquitoes, which are still present in the UK but they are not necessarily able to support the development of tropical malaria parasites and transmit them on, should they feed on an infected person.
Malaria is currently not endemic in the UK, but around 2,000 imported cases are reported annually in travellers returning from high-risk, tropical, or subtropical areas. However, malaria used to be endemic in the UK and much of Europe. It was known as 'marsh fever' or 'ague' or 'tertian fever', and predominantly affected areas of low-lying Essex, Sussex, Kent, the Somerset levels, the Yorkshire Holderness, and the Lancashire Ribble Valley. It was most likely caused by Plasmodium vivax or Plasmodium malariae, and was probably transmitted by the native mosquito Anopheles atroparvus, and also its sibling species An. messeae and An. daciae. By the 20th century it was becoming rare, especially due to extensive land drainage and better housing. The last known outbreak happened between 1917-1921 and was related to First World War soldiers coming back from the Western Front (Greece and the Balkans) and bringing the parasites with them, which then got transmitted by local mosquitoes. The last known indigenous case of malaria occurred in 1957.
Factors such as improved housing, reduced exposure to vectors, and a lack of infected people mean that it is unlikely that malaria will become endemic in the UK again.
Will we need to start wearing DEET insect repellent or sleeping under bed nets?
Wearing insect repellent containing DEET (one of the most effective active ingredients in commercial insect repellents) is a good idea if spending more time outdoors, for example when camping or sitting in the garden.
Bed nets are not relevant for the UK, as our homes are more or less "sealed boxes" and we do not have open eaves. In some places in Europe, USA and Asia, they already use window mesh screens, which allow people to keep the windows open for ventilation, but prevent insects such as mosquitoes or house flies from entering.
Why do you research mosquitoes at LSHTM?
To help protect people from vector-borne diseases, we need to understand the vector; in this case, mosquitoes. Protection in our case also means improved surveillance and control.
At LSHTM we have a long heritage in entomology and research of infectious diseases, which affect millions of people globally. Large teams of experts study malaria from all angles, including the Anopheles mosquito species, which transmit malaria parasites, while others at LSHTM study the malaria parasites and the transmission process. We also study arboviruses such as dengue, chikungunya, and others, spread by Aedes mosquitoes.
How do you carry out research on mosquitoes?
At LSHTM we have specialist insectary facilities where we breed different mosquitoes in carefully controlled environments. They provide the ideal temperatures and conditions for the mosquitoes. This enables us to study every stage of the life cycle, breeding, and behaviour. Our mosquitoes are used in research as well as teaching for our students to get hands-on experience in entomology and parasitology, for example.
Researchers also use mosquitoes in secure laboratories at LSHTM for experiments with malaria parasites and viruses to understand how they affect mosquitoes, how they move through their bodies, and potentially infect the next person - and how we could block this process.
What types of mosquitoes do you have in the insectaries at LSHTM?
We have thousands of mosquitoes in our insectaries at any one time. LSHTM maintains important collections of mosquitoes, and other vectors, in its insectaries to help scientists understand the diseases they spread.
Some colonies are descended from mosquitoes brought to the UK from countries in tropical regions decades ago.
We currently have a few different species of Anopheles mosquitoes, which are the main vectors of malaria (such as Anopheles gambiae, Anopheles coluzzii and Anopheles stephensi, the infamous vector from Asia and Middle East, which has managed to move into Africa, where it was first detected in Djibouti in 2012). We also have tropical species of Aedes and Culex mosquitoes, as well as Aedes vexans. And we have Toxorhynchites brevipalpis mosquitoes. These "giant" mosquitoes are very peculiar as they do not feed on blood at all but their larvae feed on larvae of other nuisance mosquitoes, so are in effect a type of biological natural vector control.
We also keep other vectors/arthropods of public health importance, such as sand flies (which transmit leishmaniasis), triatomine bugs (which transmit Chagas disease), bed bugs, house dust mites, and flies of Musca sorbens species, which are mechanical vectors of trachoma (caused by Chlamydia trachomatis).
Do you have any British mosquitoes?
We set up the UK's first colony of Aedes vexans mosquitoes at LSHTM in 2024. Known as floodwater mosquitoes (or, as they have been nicknamed here, 'princess mosquitoes' after we found them to be quite particular about their requirements), these are native British mosquitoes but are found in other countries as well. We brought the original ones from a laboratory in Germany although this colony originates from Utah, USA, and was taken to Germany in 1997. It has been a challenge to establish the colony here, to create the perfect conditions for the females to breed as they would in the wild.
These mosquitoes usually overwinter as eggs, which can completely dry out. Once spring arrives, days are sufficiently long, temperatures are high enough, and there is rain, the larvae will emerge from eggs as soon as the eggs get submerged/wet. They're usually found where flooding occurs, and if conditions are just right, they can emerge in large numbers.
Over time we have learnt to treat the moss they use for bedding in just the right way for the high-maintenance females to lay eggs, and the mosquitoes are now thriving in the insectary.
Next steps are to develop a parallel colony of wild UK Aedes vexans collected after flooding to compare with the laboratory colony. This will enable us to gather evidence about other arborviruses the mosquitoes could spread, supporting efforts to control the risk of climate-related infectious disease in the UK and globally.
Why are you studying Aedes vexans? Do they pose a risk in the UK?
This expertise underpins a strategic effort led by our vector biology and virology teams to build new capacity for studying mosquito-borne viruses in a changing climate.
As the world warms, several arboviruses are beginning to appear in places where they were not previously found. This shift is driven by mosquitoes moving into new areas, as well as changes in human and animal behaviour and how long viruses can survive and remain infectious.
In 2025, the UKHSA reported that fragments of West Nile virus had been detected in Aedes vexans in Nottinghamshire. Although the risk to the public is still low, it's important we monitor the situation for any signs of changes in the mosquito population.
What is the research project you have started on the Aedes vexans, and why is it important?
Research with colleagues such as virologist Professor Roger Hewson in LSHTM's secure laboratories is enabling us to test the mosquitoes' capacity to harbour and transmit arboviruses, including several viruses known to be transmitted by the species such as Rift Valley fever virus, West Nile virus, Japanese encephalitis virus, Zika virus and many others.
We are using Tahyna virus to model the relationship between the virus and the vector (Aedes vexans). Tahyna virus is found across Central and Eastern Europe and parts of Asia and potentially Africa (though that is probably another, closely-related virus). It was the first mosquito-borne virus discovered to cause human disease in Europe. The disease it causes in humans is usually mild, but in rare cases it has been linked to infections of the brain and nervous system.
Tahyna virus belongs to a large family of viruses called bunyaviruses and is closely related to more dangerous viruses, such as the Rift Valley fever virus. The virus circulates naturally between mosquitoes and wildlife such as hares and rodents. Humans become infected when they are bitten by an infected mosquito.
It is thought that the virus can pass from a mosquito to its eggs in a process called vertical transmission, allowing it to survive the winter and reappear the following year when adult mosquitoes emerge. We intend to study this further, as it is important for our understanding of disease transmission.
Our research with Aedes vexans is a crucial opportunity to get ahead of future risks. Aedes vexans are already in the UK with signs of their potential to spread viruses, along with a risk of more flooding events, so we must not ignore it.
What have you learnt from studying mosquitoes?
My interest in medical entomology started back in Slovenia, where ticks and tick-borne diseases pose a serious problem, before moving to the UK and LSHTM where my main focus is on mosquitoes. I learnt very quickly that vectors (arthropods which transmit diseases) are fascinating. Plus it is important to remember that mosquitoes are not only a biting nuisance; many of them are also pollinators and play an important role in the ecosystem.
Finding out as much as possible about their biology, ecology and pathogen life-cycles in them means we can try to predict where diseases will occur and when, and we can try to outsmart them to prevent this from happening. Are we winning? Not yet, but we're working on it.
Read the first part of our UK mosquito explainer series, Mosquitoes in the UK: What you need to know
