November 23, 2014
Rare Tapeworm Lived In UK Man’s Brain For Four Years
Eric Hopton for redOrbit.com - Your Universe Online
A Tapeworm taken from a UK man’s brain reveals genetic secretsA 50 year old UK man who began to experience distressing symptoms including seizures, headaches, strange smells and memory impairment had his doctors baffled. It took the medical team four years to find and analyze the real cause. A rare exotic visitor from the Far East had hitched a ride on the man’s brain and was burrowing its way around inside.
The unwanted guest was a tapeworm, Spirometra erinaceieuropaei, which has been reported only 300 times worldwide since 1953. This was the worm’s first ever visit to the UK and it wouldn’t be anyone’s first choice as a traveling companion.
Tapeworms are usually found living in the gut and the most common symptoms are weakness, weight loss and abdominal pain. However, the larvae of some species of tapeworm, including the rather nasty Spirometra erinaceieuropaei, can travel through the body to the eyes, brain or spinal cord and can cause inflammation of the body's tissues.
This species is so rare that very little was known about its biology and its complex lifecycle. Scientists believe that the worm enters the human body as a result of eating lake crustaceans or raw reptile and amphibian meat. Another possible route is the use of raw frog poultice, sometimes used as a traditional Chinese remedy to treat eye problems.
The patient was tested for a range of diseases including HIV, lime disease and syphilis. All test results were negative and there were no other obvious abnormalities. It was only when doctors took a series of MRI images of his brain over the next four years that the real bizarre nature of the illness became apparent. The scans showed a lesion approximately two inches long on the man’s brain. But the story took an even more alarming turn when the images revealed that the lesion was moving slowly through the brain tissue, traveling around two inches from the right side of the brain to the left.
The medical team took a biopsy from the left thalamus. They extracted a one centimeter long ribbon-shaped larval worm and realized that the unnamed patient had been suffering from Sparganosis, an infection caused by larval Diphyllobothriidea tapeworm infection. After the removal of the parasite, the man soon began to mend and has since made a full symptomatic recovery. Although we do not know at this stage how he picked up the parasite, we do know the man was of Chinese ethnicity, had lived in the East of England for 20 years, and was a frequent visitor to his homeland.
This remarkable story doesn’t end there. The remains of the extracted tapeworm enabled scientists to sequence its genome for the first time, opening up the possibility of improved diagnosis and treatment for the unwelcome invader.
A histology slide of the tapeworm was taken by the hospital and samples were sent to researchers at the Wellcome Trust Sanger Institute. Scientists at the Institute were able to sequence its DNA and establish its identify as Spirometra erinaceieuropaei. The species is normally found in China, South Korea, Japan and Thailand.
“The clinical histology slide offered us a great opportunity to generate the first genome sequence of this elusive class of tapeworms,” said Dr. Hayley Bennett, lead author of the study. Only a tiny amount of DNA was available - just 40 billionths of a gram.
With so little to work with, the researchers concentrated on sequencing one particular gene, the so-called “barcode of life.” The team also generated sufficient DNA sequence data to produce a draft genome which offers great potential to target treatments in the future.
Dr. Effrossyni Gkrania-Klotsas, study author from the Department of Infectious Disease, Addenbrooke's NHS Trust said “Our work shows that, even with only tiny amounts of DNA from clinical samples, we can find out all we need to identify and characterize the parasite.” The findings will be added to a global database of worm genomes to help identify parasites more easily and determine the best course of treatment.
The Spirometra erinaceieuropaei genome is unexpectedly large. At 1.26 billion base pairs long, this is the largest reported genome for any flatworm, ten times longer than other tapeworm genomes and one-third the size of the human genome. The large size is partly due to a greater number of genes which the researchers believe may help the parasite to break up proteins and invade its host.
By comparing these results with those from other previously sequenced tapeworm species, our understanding of Spirometra erinaceieuropaei's biology is now much deeper. “For this uncharted group of tapeworms, this is the first genome to be sequenced and has allowed us to make some predictions about the likely activity of known drugs,” said Dr. Matt Berriman, senior author and member of Faculty of the Sanger Institute. “The genome sequence suggests that the parasite is naturally resistant to albendazole - an existing anti-tapeworm drug. However, many new drug targets that are being explored for other tapeworms are present in this parasite and could offer future clinical possibilities.”
The tapeworm had genes which were resistant to benzimidazole, but showed sensitivity to another tapeworm drug - praziquantel. The team also found a number of genes which are known to respond to some cancer drugs, opening up more possible treatments.
The research has been published in the open access journal Genome Biology to provide insights into potential drug targets within the genome for future treatments.