A very rare parasite was discovered residing in the brain of a man from the United Kingdom by researchers at CUH Addenbrooke, the 1 cm long tapeworm lived there for at least four years.
The tapeworm, identified as Spirometra erinaceieuropaei, traveled 5cm from the right side of the brain to the left during that period.
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“The clinical histology slide offered us a great opportunity to generate the first genome sequence of this elusive class of tapeworms,” says Dr Hayley Bennett, first author of the study from the Wellcome Trust Sanger Institute. “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.
”To identify the exact species of worm, the researchers sequenced one particular gene, the so-called “barcode of life”. Fortunately for the patient, the gene’s DNA sequence revealed that the parasite was the more benign of the two sparganosis-causing worm species.
“We did not expect to see an infection of this kind in the UK, but global travel means that unfamiliar parasites do sometimes appear,”says Dr Effrossyni Gkrania-Klotsas, study author from the Department of Infectious Disease, CUH Addenbrooke’s.
“We can now diagnose sparganosis using MRI scans, but this does not give us the information we need to identify the exact tapeworm species and its vulnerabilities. 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.
“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. We are really lucky to be able to work closely with such an excellent facility as the Wellcome Trust Sanger Institute.”
S. erinaceieuropaei has been reported only 300 times worldwide since 1953 and has never been seen before in the UK.
Sparganosis is an infection with the larval stages of diphyllobothriid tapeworms, other than Diphyllobothrium latum, that belong to the genus Spirometra.
Most cases of sparganosis are reported from the Far East; however, cases are seen worldwide including rare reports out of the US.
The life cycle is very similar to D. latum. The adult Spirometra tapeworms live in the intestines of dogs and cats. When the pet defecates, tapeworm eggs are released into the environment. The eggs hatch in water where this stage of the parasite is ingested by copepods. The copepod is then ingested by a second intermediate host such as an amphibian or reptile where the plerocercoid larvae is developed.
When a dog or cat eats the frog or reptile, the life cycle is complete. Humans serve as an accidental host and the life cycle cannot be completed.
People typically are infected with sparganosis when they drink water contaminated with infected copepods, by eating raw or undercooked frog or snake or using the animals flesh as a poulice to an open wound.
The symptoms of sparganosis in humans depend on where the migrating larvae end up. The subcutaneous tissue is the most frequent location. Here painful nodules are the norm. If the larvae migrate to the brain, however, much more serious neurological symptoms will ensue.
Diagnosis of sparganosis is typically made by recovering the larvae from the lesion or nodule. There is currently no recommended treatment for sparganosis other than surgically removing the larval cestode.
Since sparganosis is so rare, prevention strategies in public health have not been of great importance.
The obvious preventive measures would be identifying and avoiding drinking contaminated water, not eating raw or undercooked frogs, etc and avoid poulticing inflamed lesions.
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