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World's First Case of Human Brain Infection by a Python Roundworm Identified

A carpet python's head.
Credit: David Clode/Unsplash
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Researchers from the Australian National University (ANU) and Canberra Hospital have reported the first-ever case of a human infected with a parasitic roundworm originating from a carpet python. The parasite was found, alive and writhing, in the brain of a 64-year-old Australian woman. The wriggly details have been published in the journal Emerging Infectious Diseases.

What is the Ophidascaris robertsi roundworm?

This roundworm, known scientifically as Ophidascaris robertsi, usually resides in the esophagus and stomach of carpet pythons. The worm's eggs are released with the snake's feces. Marsupials and small mammals are its usual intermediate hosts, which are then consumed by other pythons, completing the worm's life cycle. Like other roundworms, Ophidascaris is a hardy customer.

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Sanjaya Senanayake, a clinician and researcher at ANU and Canberra Hospital and co-author of the new study, said, “This is the first-ever human case of Ophidascaris to be described in the world.”  Remarkably, the roundworm found in the patient's brain was eight centimeters long. Senanayake’s team believes it may also be the first case of the parasite to be found in the brain of any mammalian species. The parasite’s eggs were found in other organs in the woman’s body, including her lungs and liver.

How did the infection occur?

The unfortunate woman, a resident of New South Wales, likely contracted the parasite when collecting a native grass known as Warrigal greens, which she used for cooking. The contamination probably happened through direct contact with the grass or from consuming it.

Symptoms and diagnosis

Her first symptoms began in January 2021 and were initially non-specific abdominal pain and diarrhea. Over time, they progressed to fever, cough and shortness of breath.

“In retrospect, these symptoms were likely due to migration of roundworm larvae from the bowel and into other organs, such as the liver and the lungs. Respiratory samples and a lung biopsy were performed; however, no parasites were identified in these specimens,” said Karina Kennedy, Canberra Hospital’s director of clinical microbiology and associate professor at the ANU Medical School.

By 2022, more alarming symptoms appeared, such as memory lapses and altered thought processing. This led to the woman getting an MRI scan, which revealed an unusual lesion in the right frontal lobe of her brain. During subsequent brain surgery, the parasite was identified.

A growing concern: Zoonotic diseases

Senanayake emphasized the increasing threat of zoonotic diseases – illnesses transmitted from animals to humans. “There have been about 30 new infections in the world in the last 30 years. 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,” he said.

While the Ophidascaris infection is not transmissible between humans, meaning there is no risk of a COVID-19-style pandemic arising from this case, the worm and its python host are not restricted to Australia. This means the likelihood of similar cases appearing in other countries in the future is high, Senanayake added.

Prevention and food safety

This rare case underscores the importance of food safety, especially when sourcing food from the wild or maintaining gardens. “People who garden or forage for food should wash their hands after gardening and touching foraged products. Any food used for salads or cooking should also be thoroughly washed, and kitchen surfaces and cutting boards, wiped down and cleaned after use,” Kennedy said.

The patient remains under close monitoring by infectious disease experts. “It is never easy or desirable to be the first patient in the world for anything. I can’t state enough our admiration for this woman who has shown patience and courage through this process,” summed up Senanayake.

Reference: Hossain ME, Kennedy KJ, Wilson HL, et al. Human neural larva migrans caused by Ophidascaris robertsi ascarid. Emerg. Infect. Dis.2023;29:9.doi:10.3201/eid2909.230351

This article is a rework of a press release issued by the Australian National University. Material has been edited for length and content.