For a year, doctors treated a 64-year-old woman from Australia for an unexplained lung issue. They tried steroids, immunosuppressants, and monoclonal antibodies. While there were some temporary improvements, her condition never fully resolved. In mid-2022, when she began experiencing memory issues and depression, a brain scan was ordered. It revealed a single lesion in her right frontal lobe. During subsequent open surgery, they discovered a live, vibrant red worm.
On August 11, 2023, Canberra Health Services announced the first known human case of infection with Ophidascaris robertsi, a parasitic roundworm found in Australian carpet pythons. The 80mm larva extracted from the patient’s brain marked a pathogen that had never been documented in humans before.
This case, featured in the Emerging Infectious Diseases journal by the US Centers for Disease Control and Prevention, detailed an infection that spread through various organs before infiltrating the central nervous system. According to the CDC report on Ophidascaris robertsi, this represents the first case of the parasite affecting a human.
From Abdominal Pain to Brain Surgery
The woman, hailing from southeastern New South Wales, visited a local hospital in late January 2021, complaining of three weeks of abdominal pain and diarrhea, along with dry cough and night sweats. A blood test indicated a peripheral blood eosinophil count of 9.8 × 10⁹ cells per liter—roughly 20 times above the normal upper limit.
A CT scan revealed several pulmonary abnormalities with surrounding ground-glass changes, a sign of potential inflammation or infection. Lesions were also spotted on her liver and spleen. Bronchoalveolar lavage indicated that 30 percent of eosinophils were present, with no pathogens detected.
The diagnosis was eosinophilic pneumonia of unknown origin, leading to a prescription of prednisolone at 25mg daily. Although her condition improved slightly, she returned three weeks later with persistent fever and cough while still on treatment. Subsequent CT scans showed ongoing liver and spleen lesions alongside persisting pulmonary opacities. A lung biopsy confirmed eosinophilic pneumonia, with cultures for bacterial, fungal, and mycobacterial infections returning negative results. Serologic tests for Echinococcus, Fasciola, and Schistosoma were also negative, as were fecal exams for parasites.
Researchers observed a monoclonal T-cell receptor gene rearrangement, indicating a potential T-cell driven hypereosinophilic syndrome. Treatment escalated to prednisolone 50mg daily and mycophenolate 1g twice daily. Given the patient’s travel history to areas known for endemic parasites decades prior, doctors prescribed ivermectin at 200µg/kg orally over two days, with a repeat dose scheduled after two weeks.
CT imaging in mid-2021 showed some improvement in her pulmonary and hepatic lesions, but the splenic ones remained unchanged. In January 2022, mepolizumab was added at 300mg every four weeks because lowering the prednisolone dose below 20mg daily led to respiratory flare-ups.
Worm Discovered in Frontal Lobe Lesion
Over the following three months in 2022, the patient experienced escalating forgetfulness and depression despite ongoing immunosuppressive treatment. A brain MRI revealed a right frontal lobe lesion measuring 13 × 10mm.
In June 2022, an open biopsy was performed, where surgeons identified a string-like structure within the lesion and extracted a live, motile helminth that measured 80mm in length and 1mm in diameter. Histopathological examination of the tissue indicated a benign inflammatory cavity with marked eosinophilia.
The research team tentatively identified the helminth as a third-stage larva of Ophidascaris robertsi based on its unique red color, three active ascaridoid-like lips, presence of a cecum, and lack of a developed reproductive system.
Independent PCR-based sequencing from institutions in Sydney and Melbourne confirmed over 99.7 percent sequence match to Ophidascaris robertsi, corroborating the findings published in Emerging Infectious Diseases.
Python Parasite’s Unusual Life Cycle
The Ophidascaris robertsi nematode is endemic in Australia, primarily hosted by carpet pythons (Morelia spilota). Adult nematodes populate the pythons’ esophagus and stomach, laying eggs in the snake’s fecal matter. Small mammals then consume these eggs, with larvae migrating to various organs. The cycle is completed when pythons ingest these infected hosts. To date, no human infections with any Ophidascaris species have been recorded.
The woman lived near a lake area frequented by carpet pythons. While she had no direct contact with the snakes, she regularly gathered native vegetation like warrigal greens (Tetragonia tetragonioides) from around the lake for cooking. Investigators suspect she may have inadvertently consumed Ophidascaris robertsi eggs either from contaminated plants or through her hands and kitchen utensils.
The clinical and radiological progression of the patient’s symptoms suggested a dynamic process of larval migration across multiple organs, showing eosinophilia in both blood and tissues—consistent with visceral larva migrans syndrome. Interestingly, Ophidascaris larvae can survive for long durations within animal hosts; lab rats have retained third-stage larvae for over four years. In this case, the patient’s immunosuppressed state might have allowed the larvae to migrate into her central nervous system, an occurrence not previously documented for Ophidascaris species.
Treatment and Recovery
After the larva’s surgical removal, the patient was treated with ivermectin at 200µg/kg for two days, along with albendazole 400mg twice daily for four weeks, to tackle any potential larvae in other organs. A tapering course of dexamethasone started at 4mg twice a day over ten weeks, while all other immunosuppressive treatments were halted.
Six months post-surgery and three months after stopping dexamethasone, the patient’s eosinophil count was back to normal range. Her neuropsychiatric issues improved but were still present. CT scans indicated that the pulmonary and hepatic lesions had resolved.
Since this case, no additional human infections with Ophidascaris robertsi have been recorded.
