Tick-borne Encephalitis Found in the UK

Peter Russell

November 01, 2019

Tick-borne encephalitis virus was found for the first time in ticks in the UK.

Tick-borne encephalitis (TBE) was detected in a small number of ticks in Thetford Forest in East Anglia, an area on the border between Hampshire and Dorset, and the Highlands of Scotland.

The findings were part of ongoing research by Public Health England (PHE) and the Emerging and Zoonotic Infections National Institute for Health Research (NIHR) Health Protection Research Unit at the University of Liverpool.

TBE is endemic in mainland Europe and Scandinavia, as well as Asia.

"I think this is now an incursion into the UK," said Jimmy Whitworth, professor of international public health at the London School of Hygiene and Tropical Medicine. He told Medscape News UK: "I don't think it's going to go away; it's likely if anything that it will expand."

Results of the research, Tick-Borne Encephalitis Virus, United Kingdom , were published ahead of print in the journal, Emerging Infectious Diseases.

Surveillance carried out between February 2018 and January 2019 from serum samples collected from 1309 deer culled across England and Scotland showed that overall, 4% of samples were enzyme-linked immunosorbent assay (ELISA) positive for the TBE virus serocomplex.

Norfolk had the highest seroprevalence detected by ELISA (51.3%), followed by Hampshire (14.3%), Suffolk (10.7%), and the Scottish Highlands (8.6%).

Viral Infection

Earlier this year a visitor from Europe became ill after being bitten by a tick in the New Forest in what was considered to be a highly probable case of TBE.

The patient, who was reported to PHE through the European Early Warning and Response System made a full recovery.

To date, no other cases of TBE considered likely to have been acquired in the UK have been identified. The risk from the virus was assessed as very low for the general population.

Advice from PHE was that anyone who felt unwell following a tick bite should contact their GP.

Prof Whitworth said symptoms were typical of a viral infection.

"You get an initial viraemic phase that lasts around a week where you have fever, fatigue, headache, myalgia, nausea," he said. "You then get an asymptomatic phase of about another week, and then you might get a second clinical phase where you get central nervous system presentation which might be meningitis, encephalitis, myelitis.

"The majority of infections will be asymptomatic. Of those that are symptomatic, only about a quarter would get that second central nervous system phase, and the case fatality rate is quoted as being less than 2%.

"Perhaps the worry is that you get severe neurological sequelae in up to 10%."

Tackling Invasive Species

Increases in temperature, rainfall, humidity, as well as milder winters were the likely cause of TBE reaching England, according to Prof Whitworth, who said migratory birds or imported pets were possible culprits.

Further work was underway to identify the distribution of TBE virus infected tick populations, PHE said.

A report last week by the Environmental Audit Committee of the House of Commons called for a "step-change" and a boost to financial resources in tackling invasive non-native species in the UK.

Expenditure on biosecurity in Great Britain was approximately £220 million per year, yet invasive species only received 0.4% of that sum (£0.9m).

The report, Invasive Species , called for spending to increase to at least £3 million a year.

Prof Whitworth backed the call for more resources. "Horizon scanning in this country is pretty good, and surveillance of incursions is good by PHE," he said. However, he added: "The UK's actually poor at taking action about incursions.

"There seems to be no plan in government for how one actually deals with incursions.

"There are no designated financial or human resources for dealing with these issues, and it's not clear who takes responsibility. So, I think there really is a need for a plan to act on what's found in these cases."

Tick Awareness

Prof Matthew Baylis from the University of Liverpool, who co-supervised the research, commented: "The discovery of a new tick-borne virus in the United Kingdom is important, as it reinforces the message that the public need to be 'tick-aware' when walking in the countryside where they may be exposed to tick bites.

"The public should take basic protective measures, such as using repellents, keeping to paths, wearing light coloured clothing, tucking trousers into socks, and checking regularly for ticks."

Lyme disease remains the most common tick-borne infection in the UK.

The risk of acquiring Lyme substantially outweighs that of acquiring TBE virus, PHE said.

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