Now, Canberra infectious diseases specialist Associate Professor Sanjaya Senanayake has published the world’s first report of human neural larva migrans caused by an Ophidascaris robertsi nematode.
“New infections are emerging all the time,” he says, “but you just don’t expect it to be your team that finds one.”
The patient, a 64-year-old woman who had travelled to South Africa, Asia and Europe decades earlier, presented to hospital in January 2021 after three weeks of abdominal pain and diarrhoea, followed by dry cough and night sweats. “She had eosinophilia with abdominal and respiratory symptoms when she first presented, so parasites were looked for,” Senanayake says.
Looked for, but not found. Stool samples, serological testing for Strongyloides, broncho-alveolar lavage, blood cultures and eventually lung biopsies were all negative for parasites (alongside other infections, autoimmune conditions and malignancy.) The patient was diagnosed with eosinophilic pneumonia of unclear aetiology.
Despite negative testing, the patient was even treated for Strongyloides as a prophylactic measure before trialing immunosuppression. This had mixed results, with CT-improvement of her lung and hepatic lesions, but in 2022 she developed memory loss and worsening depression.
Brain MRI showed an enhancing right frontal lobe lesion, and the neurosurgeon was surprised to extract an 8 cm motile worm during open brain biopsy.
Even then, the exact diagnosis was not immediately obvious, and in a story worthy of an episode of House, Senanayake recalls taking the worm to a parasitologist down the road at the CSIRO who was able to identify it quite quickly on physical inspection: a third stage larva of the Ophidascaris robertsi, found naturally in wild Canberran carpet pythons.
The patient lived close to a lake which both she and the local pythons frequent – she liked to pick Warrigal greens to use in her cooking. The working theory is that she must have ingested eggs during her culinary adventures.
While Senanayake describes this as “one of the most intriguing, interesting cases I’ve ever encountered,” he does spare a thought for the woman who suffered for over 12 months before a clear cause was found. “Behind this is a lovely patient who had to go through the protracted course of investigations and treatment. You don’t want to be an interesting patient!”
The patient was presumptively treated with ivermectin and albendazole, a decision based on what is known about other nematode infections in snakes and humans. Dexamethasone was added to decrease brain inflammation. Another year on, she is improving, although some symptoms unfortunately persist.
Senanayake laughed when I said GPs would likely be inundated this week with patients wondering if their depression was actually a worm on the brain. “Oh, us infectious diseases physicians too!” he said, “but people don’t really need to worry. It’s an infection in a person, but not infectious person to person.” However, he expects to see more cases over time, and notes that the Ophidascaris species is found in many snakes across the world.
“There are new infections appearing in the world all the time, not just the hundred-year pandemics,” Senanayake says. “About three quarters are like this, infections from the animal world that have managed to infect humans.”
“It’s a good reminder that as the human population is burgeoning and encroaching on animal habitats, we are going to see more of these types of infection,” he says.
He also sees this as evidence to support the One Health concept. “As we see more of these animal infections penetrate the human world, it is important that vets and human doctors work together, particularly in the realm of antibiotics and resistance,” he says.
Feature image courtesy of Canberra Health Services.
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