For many people, mosquitoes are simply an annoying part of summer. Their familiar buzz is usually the signal to start waving your arms, reach for the insect repellent or wonder where that itchy bite came from.
For scientists, however, that same buzz tells a much bigger story. In the Vector-borne Diseases group at the Animal and Plant Health Agency (APHA), we study pathogens that are transmitted by vectors such as mosquitoes. By identifying mosquito species, their locations, and any pathogens they carry, we can better understand how mosquito-borne pathogens move through wildlife populations and whether they pose a disease risk to animals or humans. In other words, while most people are trying to avoid mosquitoes, we are interested in finding them and discovering what viruses they might be carrying.
World Mosquito Day is an opportunity to reflect on how much we have learnt about these tiny vectors and the pathogens they can spread. It also highlights the importance of staying one step ahead of emerging health threats.
Looking for the early warning signsOne of the most important parts of our work is undertaking surveillance of mosquito-borne viruses. We analyse mosquitoes collected from different parts of the country to identify the species present, understand how mosquito populations are changing, and test them for viruses of public and animal health importance, including West Nile virus (WNV), Usutu virus (USUV) and other emerging mosquito-borne viruses.
Left: Fieldwork at London Zoo, collecting mosquito larvae from ponds across the site. Right: APHA’s Calam Bruce and UKHSA colleague Left: APHA’s Andra-Maria Ionescu. Right: Fieldwork trip collecting mosquitoes from London ZooAlongside mosquito surveillance, we analyse samples from dead wild birds of species known to be susceptible to the viruses of interest. These samples are submitted by APHA regional laboratories, collaborators such as Zoological Society of London (ZSL), and members of the public through initiatives such as Garden Wildlife Health.
People are often surprised to learn that birds are included in routine surveillance. Birds act as hosts for a range of mosquito-borne viruses, allowing them to persist in nature, while mosquitoes transmit the virus between birds, or to animals and humans, where infection may cause disease. By monitoring both, we can build a much clearer picture of how these viruses are circulating in the environment.
We also study how viruses evolve over time by analysing their genetic material, helping us understand where they may have come from and how they are changing. Together, this research helps turn surveillance results into meaningful information that supports future decision-making and government risk assessments.
The value of this work is reflected in recent findings. USUV is an emerging mosquito-borne virus across Europe and is now endemic in southeast England. The virus is classed as a zoonosis, meaning it can cause disease in humans, although this is very rare and so far, no human cases have been recorded in the United Kingdom (UK). However, the virus severely impacts Eurasian Blackbirds (Turdus merula) and in Greater London, Blackbird populations have declined by up to 50% since the virus emerged. Through our surveillance network, USUV was detected in wild birds in Scotland for the first time last year. This finding highlights how important surveillance is, because it shows how rapidly the virus can emerge in new areas and supports the notion that the UK climate is facilitating the emergence and transmission of mosquito-borne viruses.
Finding a virus is only the beginning Culex modestus larvae. Culex modestus is considered an important vector for transmitting WNV between birds and mammals, and has been implicated in outbreaks of the disease in humans and horses in EuropeSurveillance tells us what is happening in the environment, but additional research is needed to understand why it is happening and what it might mean for animal and human health.
When a virus is detected, our work is just beginning. Once we detect it, we need to answer questions such as: Can native UK mosquitoes transmit it? Which mosquito species are involved in transmission? How quickly can we detect it?
One of the questions we investigate is whether mosquitoes found in the UK can become infected by a virus and be able to transmit it onwards when they feed again. Scientists call this a vector competence study. At the APHA, we have specialist, secure, laboratories where we can investigate if mosquitoes are able to transmit viruses. We work with native UK mosquitoes, but also with exotic, invasive mosquitoes which may inhabit the UK in the future.
To most people, a mosquito is just a mosquito. To us, the differences matter. Different species behave differently, feed on different animals, and vary in how effectively they can transmit viruses. Understanding these differences helps us identify which species may pose the greatest risk and where surveillance efforts should be focused.
Working together through a One Health approach Mosquito trapping alongside colleagues from UKHSAMosquito-borne diseases do not respect organisational boundaries. Many of the viruses involved circulate between wildlife, mosquitoes, domestic animals and, sometimes, people. Addressing these threats requires collaboration across sectors, which is why our work follows a One Health approach that recognises that animal, human and environmental health are closely interconnected.
Our research brings together experts from many different fields, including virology, entomology, wildlife health, veterinary science and public health. We work closely with partner organisations across the United Kingdom, such as the United Kingdom Health Security Agency (UKHSA) and the ZSL to share knowledge and data, monitor diseases and build a more complete picture of disease risk, so that we are able to respond more effectively if new threats emerge.
Preparing for tomorrow's challenges Mosquito collection in the field (APHA’s Sanam Thakkar and Insiyah Parekh)The value of surveillance extends beyond the laboratory. The evidence we generate helps inform how the UK prepares for future disease threats and shape policy making. Following the detection of WNV genetic material in mosquito samples from 2023, an updated national contingency plan for WNV has been published. This ensures that, should the situation change, the UK has an up-to-date framework for surveillance, investigation and response.
As our environment continues to change, so will the challenges posed by mosquito-borne diseases. By combining surveillance with laboratory research and working collaboratively across the One Health community, we are building the knowledge needed to protect wildlife, livestock and public health.
This World Mosquito Day, it is worth remembering that behind every mosquito tested and every bird sample analysed is a team of scientists working behind the scenes to protect animal and public health. Our job is not simply to respond to mosquito-borne disease threats, but to stay one step ahead of them.
seen at 09:50, 20 August in APHA Science Blog.