X-ray images of the tapeworm in the man's brain. Pic: Genome Biology 2014
A rare tapeworm lived in a man's brain for four years before being removed by scientists.
The British researchers who performed the operation say the parasite had travelled five centimetres from the right to the left side of the 50-year-old's brain during the infection.
They say the 1cm-long creature has never been seen before in the UK and has only been reported 300 times worldwide since 1953.
Known as Spirometra erinaceieuropaei, the worm causes inflammation of body tissues - which can lead to seizures, memory loss and headaches.
It is thought to be caught by accidentally eating small infected crustaceans from lakes, eating raw amphibian or reptile meat, or by using a raw frog poultice that is a Chinese remedy for sore eyes.
The Wellcome Trust Sanger Institute said the surgeons who removed the tapeworm reported the patient was now "systemically well".
Effrossyni Gkrania-Klotsas, of the Department of Infectious Disease at Addenbrooke's NHS Trust, said: "We did not expect to see an infection of this kind in the UK, but global travel means that unfamiliar parasites do sometimes appear.
Close-up of a tapeworm's head (file pic)
"Our work shows that, even with only tiny amounts of DNA from clinical samples, we can find out all we need to identify and characterise the parasite."
She added that the team managed to sequence the worm's genome for the first time, allowing them to examine potential treatments.
Dr Hayley Bennett, first author of the study from the Wellcome Trust Sanger Institute, said: "The clinical histology slide offered us a great opportunity to generate the first genome sequence of this elusive class of tapeworms.
"However, we only had a minute amount of DNA available to work with - just 40 billionths of a gram - so we had to make difficult decisions as to what we wanted to find out from the DNA we had."