Patient’s tingling feet turns out to be a rat-borne brain parasite

A tingling sensation in your feet is usually the result of poor blood circulation. But every so often, it’s an indicator of a much more nightmarish scenario: parasites setting up shop in your brain after previously incubating in rodents, slugs, and snails. This was unfortunately the recent situation for a 30-year-old woman, whose bout of angiostrongyliasis (also known as rat lungworm disease) was recently highlighted in a recent New England Journal of Medicine case study.

What is rat lungworm disease?

Rat lungworm disease is caused by the body’s immunoresponse to the parasite Angiostrongylus cantonensis. A. cantonensis begins its life cycle after a rat eats an infected snail or slug. Once ingested, the parasite migrates to the rodent’s lungs and lays eggs. After becoming first-stage larvae, A. cantonensis is excreted in the rat’s feces that snails and slugs subsequently eat. The parasite larvae then matures inside the gastropods, allowing the cycle to repeat.

But sometimes other animals—and even plants—can get involved, laying the groundwork for human transmission. Species like land crabs and freshwater prawns also snack on the infected slugs and snails, which can increase the parasite’s spread. Meanwhile, larvae are sometimes deposited in gastropod slime as they move across fruits and vegetables. Humans can then become hosts after eating improperly washed leafy vegetables or undercooked crustaceans. Some combination of these reasons is likely how the patient contracted her bout of rat lungworm disease.

A travel nightmare

In this case study, the patient’s symptoms appeared relatively innocuous at first. A few days after returning from a three-week overseas trip that included stops in Japan, Thailand, and Hawaii, the woman began experiencing a mild burning sensation in her feet.The burning soon crept up her legs and was combined with acute fatigue. She originally attributed the issues to jet lag, but the pain eventually increased and she began to get severe headaches.

Results from her first emergency room visit only showed a slight increase in white blood cell count, indicating she was fighting off at least some type of infection. With no solution and conditions worsening, the woman visited a different hospital a few days later, this time also with a mild fever. Intravenous anti-inflammatory and anti-anxiety medications appeared to finally help her, after which doctors once again discharged her.

The woman began packing for another vacation after waking up the next day. However, there was a bit of a problem—she never actually booked a second trip. The patient’s roommate noticed the confusion and encouraged her to go back to bed while informing the woman’s partner of the concerning behavior. A few hours later, she found herself at the hospital yet again. 

Further blood tests and a CT scan didn’t show any evidence of parasites. Finally, a lumbar puncture to assess her cerebrospinal fluid revealed signs of a rare brain infection caused by parasites known as eosinophilic meningitis. After reviewing her recent travels and ongoing, worsening symptoms, doctors finally believed they could confidently identify the culprit: Angiostrongylus cantonensis.

A healthy outcome

Angiostrongyliasis can be serious if left untreated. In 2010, for example, a 19-year-old Australian man became ill after consuming a live slug on a drunken dare. The patient eventually entered into a nearly 14-month coma that left him paralyzed from the waist down until his death from related complications in 2018. 

In this recent case, the situation does appear to be much less dire. After six days in the hospital and a two-week drug regimen that included prednisone, albendazole, and other medications, the patient appears symptom-free and in much better health without the unwanted invaders in her body.

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