April 5, 2023

expert reaction to UKHSA press release suggesting that tick borne encephalitis is now likely to be present in England

A new risk assessment, published by a multi-agency cross-government committee, reports that tick borne encephalitis is now likely to be present in England.

Dr Benjamin Brennan, Wellcome Trust/Royal Society Sir Henry Dale Fellow at the MRC-University of Glasgow Centre for Virus Research, University of Glasgow, said:

“Tick-borne encephalitis virus (TBEV) is a disease transmitted primarily by Ixodes species ticks.  Disease symptoms can range from a mild flu-like illness to severe infection of the central nervous system, which can be fatal.  UKHSA have reported the first confirmed human cases of TBEV acquired from UK ticks.  TBEV was first detected in ticks in England in 2019, so it is now unsurprising that we are starting to see reports of the transmission of the virus to people in different parts of the UK.  TBEV is not just an issue for humans, companion animals such as dogs at risk of tick bites are also at risk of contracting the disease if bitten by an infected tick.

“Climate change is causing ticks to move into new geographical areas and extending the season in which they are active, increasing the risk of tick-borne disease transmission.  While there is a vaccine available to treat TBEV, the best way to prevent contracting TBEV is to be tick-aware and to stay tick-safe when accessing the countryside.  If anyone develops flu-like symptoms following a tick bite they should contact their healthcare provider or GP immediately.”

Prof Roman Biek, Professor of Disease Ecology and Molecular Epidemiology, University of Glasgow, said:

“These human cases are not a surprise – ticks infected with the virus had been detected in the UK in recent years and there had been suspected cases.  What is unexpected, are the locations of these human cases, as they occurred at some distance from where the virus had been found previously.  This indicates that the virus is more widely distributed in the UK than we had anticipated.

“The virus has clearly become established in multiple places in the UK, most plausibly as a consequence of infected ticks travelling on migrating birds.  The opportunities for this to happen would have existed for a long time.  So why these introductions were successful only recently, as suggested by the data available so far and similar timelines of emergence in other European countries, is not clear.  Identifying the environmental conditions, or changes to these conditions, that played a role in TBEV emergence, is an obvious research priority right now.

“Luckily, the chances of becoming infected are low and the same measures that are recommended to protect yourself from tick bites in general, will also be the first line of defence against this virus.  This means being ‘tick-aware’ and includes covering your legs and ankles, using insect repellent, and checking yourself and your clothes after spending time outdoors.”

Prof Sally Cutler, Professor of Medical Microbiology, University of East London, said:

“The presence of tick-borne encephalitis virus (TBEv) has been noted at low levels in ticks in UK since 2019, so this is certainly on the radar for those interested in tick-borne diseases.  There is also a problem with expansion of ticks and some tick-borne pathogens in response to multi-factorial human influences such as climate change, land fragmentation and behavioural influences.  This is just another example of these factors.  We should keep monitoring and publicising these findings to ensure diagnosis and prompt treatment of cases.  The virus comes in different variants, and that being detected in the UK to date has been one of the milder variants.  Vaccines are used to protect populations in highly endemic areas, but we probably are not yet in a situation whereby we need this level of protection at this time.  Certainly we need to ensure we monitor the situation, but this report confirms previous observations.”

Prof Ian Jones, Professor of Virology, University of Reading, said:

“Tick Borne Encephalitis Virus (TBEV) was reported in ticks in Thetford forest in 2019 and today’s update would suggest that it has now become established at other sites and caused sporadic disease in people.  Genetically the UK viruses have been close to European or Scandinavian strains so they may have originally arrived from the near continent in ticks attached to birds.

“The virus is found naturally in some ticks and gets transferred to a person if they are bitten (only if the tick is infected), usually on bare arms and legs whilst walking through undergrowth.  Wearing appropriate clothing essentially removes the risk.

“Now here, it’s unlikely that TBEV will disappear, but the general threat level is very low and there is no reason to suppose cases in people will be any more than sporadic in nature.  A vaccine is used in areas of high incidence in Europe and could be considered here for individuals with outdoor occupations in areas where the virus is found.  For the general public however, the risk is minimal.”

https://www.gov.uk/government/news/tick-borne-encephalitis-detection-in-england

Declared interests

Dr Benjamin Brennan: “None.”

Prof Roman Biek: “I should mention that I am part of a large research consortium studying environmental drivers and solutions for tick-borne diseases in the UK (https://ticksolve.ceh.ac.uk/), which also includes researchers from UKHSA (though not the authors of the current study).”

Prof Sally Cutler: “No conflicts of interest.”

Prof Ian Jones: “No conflicts.”