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Good News Everyone: We Found a New Species of Roundworm That Can Infect Our Brains

In a report this week, doctors have documented the first case of a human brain infection caused by a roundworm normally found in Australian snakes.

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Here’s some extra material for your nightmares: In a case report out this week, a group of scientists say they’ve found a new species of roundworm that’s capable of infesting our brains—one that normally plagues snakes. The discovery was made when they extracted a living worm from an Australian woman’s head during surgery. Thankfully, the woman’s parasitic invasion appears to have been successfully treated.

The horrifying medical tale was detailed in a paper published Monday in the journal Emerging Infectious Diseases. According to the report, the 64-year-old woman was first hospitalized in early 2021 with symptoms of long-lasting abdominal pain and diarrhea, as well as dry cough and night sweats. Initial tests found signs of pneumonia (lung inflammation) and lesions along her liver and spleen, but they couldn’t identify a clear culprit for her illness, such as a bacterial infection or cancer.


She was diagnosed with pneumonia linked to the build-up of eosinophils, a type of white blood cell, and was eventually discharged and prescribed steroids. Though the treatment did seem to help a bit, the woman was hospitalized again within a month. Tests showed that her body was still producing more eosinophils than usual, which can be life-threatening if not managed properly, but again failed to find any cause as to why this was happening. She was diagnosed with hypereosinophilic syndrome and continued to take steroids.

The woman’s brain scan, along with the worm discovered inside her lesion.Image: Hossain et al/Emerging Infectious Diseases
The woman’s brain scan, along with the worm discovered inside her lesion.Image: Hossain et al/Emerging Infectious Diseases

The woman’s health improved for a time, and she was even starting to be weaned off her treatment. But by early 2022, she began to experience worsening depression and trouble remembering things. MRI scans then revealed a lesion in her brain. In June, her doctors decided to perform a biopsy (collecting a sample of tissue for examination) and that’s when they made the shocking find—quite literally pulling out a starkly red, living nematode from within the lesion that was about three-inches long.

While rare, there are several known species of worms that can cause brain infections in humans. But the creature’s distinct coloring made it clear to the scientists that this was no typical brainworm. Soon enough, they identified their specimen as a third-stage larva of Ophidascaris robertsi, a parasitic roundworm seen in carpet pythons, snakes found throughout Australia and neighboring regions. Genetic testing confirmed their suspicion, making this the first documented case of a human brain infection caused by this particular worm.

The woman reported no direct contact with carpet pythons, but she did live in a lake area known to have them. Her doctors also note that she would routinely collect vegetation around her home to use for cooking. They hypothesize that she either directly ate worm eggs from these vegetables or was exposed to them through her contaminated hands or the kitchenware used to prepare the food. Her initial progressing symptoms also suggest that the worms had spread to multiple organs, the authors say. Ironically enough, her later steroid treatment might have allowed the infestation to eventually reach her brain by suppressing her immune system.

These worm infestations often don’t cause visible symptoms, and they tend to clear up on their own without the need for treatment. The worms themselves can’t mature into full-grown adults and eventually die off. However severe infestations usually require antiparasitic medication to prevent living worms from causing more trouble.


In this case, the doctors found no further evidence of worms in the woman’s brain. But to root out any remaining invaders in her body, she was given deworming medication, along with a less intense course of steroids (worms dying can trigger an overzealous immune response). Six months after her surgery and three months after being tapered off steroids, her eosinophil levels had returned to normal. Unfortunately, the woman’s neuropsychiatric symptoms had improved but not completely recovered by that time.

Brain worms of any kind are not very common. But this incident does reflect what can happen when humans come into contact with wild animals and their parasites, the authors say. And it’s likely that there are other currently unknown species of roundworm out there that can call our brain home, they warn.


“In summary, this case emphasizes the ongoing risk for zoonotic diseases as humans and animals interact closely,” they wrote. “Although O. robertsi nematodes are endemic to Australia, other Ophidascaris species infect snakes elsewhere, indicating that additional human cases may emerge globally.”