Disease-carrying ticks now surviving to adulthood in UK heatwaves, UKHSA expert says

Disease-carrying ticks are surviving into adulthood in the UK thanks to heatwaves, the UK Health Security Agency’s head of medical entomology has told the Press Association.

Hyalomma ticks arrive in Britain by latching on to migratory birds from the Mediterranean and Africa as nymphs — the middle, poppy-seed-sized stage of the tick life cycle. Until now the UK has not been warm enough for them to moult into the adult stage. But Dr Jolyon Medlock, head of medical entomology at UKHSA, said heatwave years are changing that.

“They would normally come in on migratory birds as a nymph, and then fall off, and they wouldn’t be able to moult. It’s not warm enough,” Dr Medlock told PA. “What we’re seeing now in heatwave years is that they can moult through to the adult stage, and we then could be able to pick up records of adults through our tick surveillance.”

Adult records have happened “less than probably five times in the last 10 years or so”, he said, but officials and colleagues across northern Europe are starting to pick them up more often. Records show hyalomma nymphs on migratory birds at UK observatories going back 50 years; the UKHSA Tick Surveillance Scheme has mapped and monitored ticks since 2005.

Hyalomma ticks are the main transmitter of Crimean-Congo haemorrhagic fever (CCHF), a potentially severe and life-threatening virus. Dr Medlock stressed the findings do not confirm a public danger: “It doesn’t mean the tick will survive, and it doesn’t necessarily mean it’s an infection risk.”

The government’s HAIRS risk assessment notes there have been no locally acquired human CCHF cases in the UK, the virus has never been found in a UK tick, and the probability of infection for the UK population is considered “Very Low”.

Sources: Press Association via Messenger Newspapers, GOV.UK HAIRS risk assessment