Pathogen and Vector Biology

The aim of this Theme is to boost the UKHSA’s capability to monitor and better understand vector-borne pathogens in relation to their emergence and spread. It will support UKHSA's capacity to respond to new threats, collaborate within a broader science base, and build on its vigilance in the face of growing risks of vector-borne disease, as climate change and increasing globalisation impact on vector and pathogen distributions.

The Theme will develop a better understanding of the genetic diversity and evolutionary opportunities open to emerging pathogens and their vectors, highlight risks to public health and generate new capabilities for vector-borne disease control.

The long-term objectives are to become a centre of excellence for the testing of indigenous mosquitoes and ticks for pathogens that require high containment and to catalyse new funding from external grants and sustain capability for the UKHSA. 

Project 3.1: Molecular tools for Tick-borne encephalitis virus (TBEV)

Professor Roger Hewson

Theme Lead
UK Health Security Agency

Mollie Curran-French

PhD Student
UK Health Security Agency

This study will utilise recombinant virology techniques to study the pathogenicity of tickborne encephalitis virus (TBEV) and support TBEV bio surveillance programmes. TBEV is an emerging public health threat across Europe and Asia, with the expansion of risk areas into new regions and the emergence of new endemic areas. Studying virus pathogenicity and prevalence is therefore an essential component of the ongoing public health response. Project work will build new capability to tackle the current threat and develop means to investigate other emerging tick borne flaviviruses. The three main subtypes: European, Far Eastern and Siberian (and two additional members Baikalian and Himalayan), show different degrees of neuro invasiveness and neurovirulence, which may explain the different clinical courses observed.

Project 3.2: Evaluation of mosquito-borne virus transmission risk in the UK

Professor Matthew Baylis

Theme Co-Lead
University of Liverpool

Nicola Seechurn 

PhD Student
University of Liverpool

West Nile virus is an arbovirus of public health and veterinary significance due to its ability to cause symptoms in humans and clinical signs in horses and birds. Approximately 80% of human cases are asymptomatic, whilst 20% develop West Nile Fever (WNF) and around 1% develop neuroinvasive diseases. As of yet, there have been no medical or veterinary reports of locally acquired WNV in the UK, however this was also true in the United States prior to WNV introduction in 1999. WNV caused 40,000 human cases and 1,600 deaths in the first ten years following its introduction into the US and WNV bridge vector, Culex modestus is now established in North Kent, Essex and potentially other areas of South East England. Given this and the recent locally acquired bird case of WNV in the Netherlands, this highlights the importance of assessing the risk of WNV transmission should it enter the UK.

In addition to this, Usutu virus (USUV) has very recently been identified in an outbreak of birds in Greater London. This was five Eurasian blackbirds (Turdus merula) and one house sparrow. USUV has additionally been found in other birds and mosquitoes since, suggesting autochthonous transmission. USUV is also a flavivirus and closely related to WNV. It has been shown that WNV and USUV can co-circulate within the same enzootic cycle and ecological habitat. Given the very recent outbreak of USUV and the ever-increasing risk of WNV introduction into the UK, this project aims to assess the current prevalence of these viruses in mosquito and bird populations in the UK. We also aim to further understand the significance to USUV to public health and assess the host-preferences of Culex pipiens. We also aim to develop FTA cards as a screening tool for WNV and USUV vectors with the aim of increasing preparedness, planning and responsiveness should these viruses enter the UK.

Project 3.3: Investigation of Wolbachia-based vector control strategies for West Nile virus

Dr Grant Hughes

Theme Co-Lead
Liverpool School of Tropical Medicine

Sara Rooney

PhD Student
Liverpool School of Tropical Medicine

Culex modestus is an invasive mosquito species known as a key vector of West Nile Virus (WNV) in continental Europe. Although to date no WNV has been reported in the UK, recent introduction into the Netherlands and Germany highlight the importance of increasing our understanding of vector competence and identifying potential control strategies. We will evaluate UK arthropod vectors for their symbiont microbiota to examine their suitability for Wolbachia-based control or other symbiotic control strategies. We have reached out to collaborators and have sourced samples of Culex modestus which will be used for microbiome sequencing. We have completed fieldwork in Kent, UK over the summer of 2021, collected Cx modestus samples and attempted to colonize them in the lab. We have sourced samples of UK West Nile vector species that will be screened for native Wolbachia infections. Characterising these existing infections will allow us to examine the potential pathogen blocking ability of native and non-native Wolbachia strains. This work will increase our knowledge of invasive and emerging vector borne pathogens in the UK and, in turn, this will support research into controlling these pathogens.

Project 3.4: Tick-borne viruses in the UK

Dr Jolyon Medlock

Theme Co-Lead
UK Health Security Agency

Maya Holding 

PDRA
UK Health Security Agency

Core activity includes human serosurveillance focused on at risk groups. Much of this work is driven by seasonal changes, although the projects ecological propensity has enabled much of the work to continue, This will assist in assessing the risk to human health and feed into the Joint Committee on Vaccination and Immunisation’s assessment of any requirement for TBEV vaccination in the UK population. The project also aims to further knowledge of the characteristics and requirements of TBEV ecological niches through small mammal and questing tick field studies and modelling work. In addition, the threat to the UK population will be assessed through a serosurveillance study of individuals who are at increased risk of tick-bites in areas where TBEV has been identified.

The investigation of the current presence and potential spread of TBEV in the UK will assist in informing local health professionals of the potential risk of human cases in their area, particularly for consideration as a differential diagnosis of encephalitic cases with a history of tick-bite.