For the first time, scientists have sequenced the genome of a rare tapeworm removed from the brain of a 50-year-old Chinese man in the UK. The tapeworm – Spirometra erinaceieuropaei – is one parasite responsible for a disease called sparganosis, and researchers say the new information they have gathered from the sequencing may lead to new treatments for the infection.
Since 1953, the S. erinaceieuropaei tapeworm has only been reported 300 times worldwide and, prior to this latest discovery, had never been seen in the UK. Because the tapeworm is rare, researchers have struggled to learn more about it and how it causes infection in humans.
It is believed, however, that humans can accidentally consume crustaceans infected with the tapeworm, or eat raw meat from reptiles and amphibians that are infected. It may also enter the human body through use of a Chinese medicine – raw frog poultice – that eases sore eyes.
When S. erinaceieuropaei – or another member of the Spirometra family – enters the body, it can cause an infection called sparganosis, which results in inflammation of body tissue. If the tapeworm moves to the brain – known as cerebral sparganosis – it can cause headaches, seizures and even memory loss.
The man detailed in this latest study was diagnosed with cerebral sparganosis after a tapeworm showed up on brain scans. The research team – including first author Dr. Hayley Bennett of the Wellcome Trust Sanger Institute in the UK – says they were surprised to discover such an infection in the UK, but that global travel makes it possible.
The tapeworm – around 1 cm in length – had traveled 5 cm from the right side of the man’s brain to the left. After having the tapeworm surgically removed, the researchers say the man is doing well.
But with this rare occurrence, the team saw an opportunity to learn more about the tapeworm that had infected this man.
The tapeworm was placed on a clinical histology slide and the researchers subjected it to genome sequencing.
To determine the exact species of the tapeworm, the team focused on a gene they refer to as the “barcode of life.” The sequencing of this gene confirmed it was the S. erinaceieuropaei tapeworm, which is one of the more benign classes of sparganosis-causing tapeworms.
What is more, the researchers were able to gather enough data from the small amount of DNA they had from the tapeworm – only 40 billionths of a gram – to create a “draft” genome. Although this is a genome whereby some segments of DNA are missing or in the wrong order, the team hopes it will help discover potential treatment targets for sparganosis.
Close analysis of the tapeworm’s genome revealed that it was 10 times larger than genomes of other tapeworms and a third of the size of the human genome.
The team also found that S. erinaceieuropaei is naturally resistant to an already existing tapeworm drug called albendazole, but that it holds some sensitivity to another tapeworm drug, called praziquantel.
Furthermore, the researchers identified a number of genes that are known to be targets for cancer drugs. The team says such drugs could be adapted to treat sparganosis.
Commenting on their findings, Dr. Bennett says:
“This emphasizes just how important a global database of worm genomes is to allow us to identify the parasite and determine the best course of treatment. Additionally, this information can be paired with our work in global travelers’ infection to give additional insights in what infections other patients can get in specific destinations.”
Last year, Medical News Today reported on another study by researchers from the Wellcome Trust Sanger Institute, in which they suggested that cancer drugs could be used to treat two diseases caused by tapeworms – echinococcosis and cysticercosis.