Diagnostic dilemma: Woman’s lung infection, organ damage and forgetfulness caused by a parasite never before seen in humans

Patient: 64-year-old female resident of New South Wales, Australia

Symptoms: The woman was admitted to the hospital after experiencing abdominal pain and diarrhea for three weeks. She also had a persistent dry cough and night sweats.

A CT scan of her lungs showed opaque areas of thickened tissue, likely caused by inflammation or infection, where the air spaces in the lungs fill with fluid, pus, or a buildup of white blood cells. The woman also had lesions, or areas of damaged tissue, in her liver and spleen.

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When doctors took fluid from the patient’s lungs, they found an abnormally high proportion of eosinophils, a type of white blood cell that fights infection. At that time, they diagnosed the woman with a rare lung disease called eosinophilic pneumonia and prescribed the steroid prednisolone daily, which alleviated some of her symptoms. They noted that the cause of the lung infection is unknown.

What happened next: Three weeks later, the woman came to the hospital complaining of a cough and fever, even though she was still taking prednisolone, and the organ lesions had not healed.

Further tests failed to determine the cause of her breathing difficulties. Tissue sample cultures showed no signs of bacterial or fungal infection. Blood tests revealed that her immune system did not produce antibodies against various parasitic flatworms, such as fluke worms (schistosoma) and liver fluke worms (fluke worms). Her stool samples also had no evidence of these parasites.

Doctors advised the patient to continue taking prednisolone and also prescribed ivermectin, a drug used to treat parasites, since the patient had told doctors he had traveled to a country where parasites are common.

However, her respiratory symptoms persisted and worsened when she tried to reduce her prednisolone dose. Her condition remained unchanged for several months.

Diagnosis: Approximately one year after the first hospital visit, the woman began to show signs of depression and became forgetful. Doctors ordered an MRI scan of her brain, which detected a lesion in her right frontal lobe. An incisional biopsy was then performed to expose and examine the injured area. That’s when they discovered “string-like structures” inside the lesions, which they identified as live parasites called helminths, according to her case report.

The insect was bright red, approximately 3 inches (80 millimeters) long, and 0.04 inches (1 millimeter) thick.

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Treatment: Doctors removed the worms from the woman’s frontal lobe and examined the surrounding tissue and found no parasites. They gave her two days of ivermectin, this time combined with four weeks of albendazole, a broad-spectrum drug used to treat helminth infections, to kill any remaining parasites in her organs.

Because albendazole is absorbed into the central nervous system more quickly than ivermectin, these drugs have previously been used together to treat nematode infections in humans and snakes. The patient also received 10 weeks of the corticosteroid dexamethasone to prevent further inflammation.

Six months after surgery and three months after the end of dexamethasone treatment, the patient’s lung and liver lesions had disappeared, her white blood cell count was normal, and her neuropsychiatric symptoms had improved.

What’s unique about this case: Doctors identified the worm as a third-stage larva of Ophidascaris robertzi, a parasitic nematode native to Australia. Although adults breed in the carpet python (Morelia spilota), the nematode can infect other animals during the larval stage of its life cycle.

Carpet pythons were often seen near the woman’s lakeside home, and although she had no recollection of direct contact with them, she often foraged wild vegetables for cooking. The case report authors suggested that she likely became infected after touching or eating plants contaminated with O. robertsi eggs. After the eggs hatched, the larvae migrated to her organs.

This longevity of larval infection was not uncommon, as laboratory rats can host O. robertsi larvae for more than four years, according to the report. However, no human infections with this parasite have ever been recorded, and larvae of the parasite have never been found in a host’s brain.

For more interesting medical cases, check out our Diagnostic Dilemma archives.