A woman complaining of forgetfulness and depression found a cause no one could expect when astonished doctors pulled out an 8cm roundworm nestled in her brain.

The live Ophidascaris robertsi roundworm was extracted – still ‘wriggling’ – from the brain of the anonymous 64-year-old New South Wales woman at Canberra hospital.

It marks the first case of the parasite, typically found in carpet pythons, being found in a human.

“To our knowledge, this is also the first case to involve the brain of any mammalian species, human or otherwise,” Sanjaya Senanayake, Australian National University and Canberra Hospital infectious diseases specialist, told Neuroscience News.

“Normally the larvae from the roundworm are found in small mammals and marsupials, which are eaten by the python, allowing the life cycle to complete itself in the snake.”

Road to diagnosis

The patient was first admitted to a local hospital in January 2021 following weeks of abdominal pain, diarrhoea, dry cough and night sweats.

She was treated for pneumonia, but did not recover fully, and was hospitalised weeks later, leading to further testing.

In 2022, the patient began experiencing forgetfulness and worsening depression, and underwent an open brain biopsy in June that year – leading to the discovery of the live roundworm.

Dr Senanayake told The Guardian it was a “once-in-a-career” finding, which had the hospital team scrambling for answers on what type of worm the specimen was.

“We just went for the textbooks, looking up all the different types of roundworm that could cause neurological invasion and disease,” he said.

“Canberra is a small place, so we sent the worm, which was still alive, straight to the laboratory of a CSIRO scientist who is very experienced with parasites.

The 8cm long parasite in all its glory. Photo: Emerging Infectious Diseases

“He just looked at it and said, ‘Oh my goodness, this is Ophidascaris robertsi’.”

The patient lived near a lake area inhabited by carpet pythons. While she had no direct contact with snakes, she often collected native vegetation, such as Warrigal greens, from around the lake to use in cooking.

Experts hypothesise she inadvertently consumed the roundworm’s eggs either directly from consuming the vegetation, or indirectly through contamination of her hands or kitchen equipment.

Following her surgery, the patient was also treated for larvae that may have migrated to her other organs. She is now recovering, and still being regularly monitored.

Risk of zoonotic infections

A study of the case found the first human parasitic infection of its kind to be reported emphasises the ongoing risk for diseases being transmitted from animals to humans.

“There have been about 30 new infections in the world in the last 30 years,” Dr Senanayake said.

Of the emerging infections globally, about 75 percent are zoonotic, meaning there has been transmission from the animal world to the human world. This includes coronaviruses.”

“This Ophidascaris infection does not transmit between people, so it won’t cause a pandemic like SARS, COVID-19 or Ebola.

“However, the snake and parasite are found in other parts of the world, so it is likely that other cases will be recognised in coming years in other countries.”