It was the start of a medical mystery that’s the subject of a New England Journal of Medicine case study this month. In an 11-page paper published February 12, doctors at Massachusetts General Hospital in Boston and the University of Washington detail how the woman sought help at three hospitals as her symptoms got worse before she was diagnosed with parasitic worms infesting her brain.
“It’s just so unusual,” said Robert Cowie, a research professor at the University of Hawaii and an expert in the parasitic worm that infected the woman.
After a week of these symptoms, the woman made a second emergency room visit as the burning feeling and her headache got more painful. Her exam was “reportedly normal,” save for an elevated immune-cell count seen in her blood test. She was discharged with advice to follow up with her primary care physician.
But the next morning, she awoke confused. She started packing for a vacation that was nonexistent and could not be dissuaded by a family member. When the confusion continued for several hours, her partner brought her to Massachusetts General.
Doctors there documented that she had returned from a three-week trip to Thailand, Japan and Hawaii 12 days earlier. They noted that she ate street food in Bangkok – although none of it was uncooked – along with raw sushi in Tokyo and salad and sushi throughout her 10 days in Hawaii. She also swam in the ocean several times there.
A spinal tap revealed she had extremely high levels of eosinophils, white blood cells that fight off parasites and other invaders.
Doctors concluded she’d been infected with the parasitic worm Angiostrongylus cantonensis, more commonly known as rat lungworm. Although rodents alone host the adult form of the parasite, their faeces pass its larvae to snails and slugs, which can transmit the worm to humans. The larvae that infect people never mature enough to reproduce, but can survive long enough to wreak havoc.
Cowie, a rat lungworm expert who was not involved in the woman’s care, said doctors “took forever” to figure out what was ailing the patient, based on the case study.
Cowie said it’s the most recent example supporting his years-long rant about how “blissfully ignorant” most doctors are about the rat lungworm disease, or eosinophilic meningitis. That ignorance could result in harm to patients who need to take anti-worm medication quickly to avoid potentially life-changing or deadly consequences.
Rat lungworms cause symptoms that range from nonexistent to headache, stiff neck, tingling or painful feelings in the skin, low-grade fever, nausea, and vomiting, according to the Centers for Disease Control and Prevention. When rat lungworm illness was on the rise in Hawaii in 2017, one woman described her experience as akin to the pain of giving birth every day – maybe even worse. “That was like eating ice cream compared to this,” she told KHON at the time. “It was like someone stuck an ice pick in my collarbone, in my chest and in the back of my neck.”
Occasionally, it can cause paralysis or death, as was the case in 2010 when a young Australian rugby player named Sam Ballard ate a slug on a dare from his friends. The parasite infested his brain, putting him into a coma for more than a year and leaving him paralysed. He died in 2018 at the age of 29.
People have got infected by eating raw or undercooked snails or slugs, a common practice in some cultures, the CDC reported. Some children got sick by swallowing them “on a dare” while others were infected by eating snails or slugs that had been accidentally chopped up in raw produce, salads or vegetable juices. Scientists have also found rat lungworm infections in other animals, such as freshwater shrimp, crabs and frogs.
Human outbreaks of rat lungworm have involved a few people to hundreds, the CDC reported. In total, more than 2800 cases have been reported in about 30 countries, although that figure dates back to research published in 2008. Cowie said he’s collaborating with a research partner in China who’s documented at least 7000 cases.
Researchers have recorded about 220 cases in the United States, the vast majority of those in Hawaii, where the disease was first documented in 1959. In the continental United States, there have been a handful of cases, almost entirely in southeastern states such as Florida, Alabama, Louisiana, and Texas.
Cowie said he thinks the disease might have spread well beyond what scientists have documented. He said he’s working on a grant proposal to figure out how much the parasite has spread in slugs and snails in the southeast because of climate change and other factors.
“It could be that the parasite is more widespread than we know,” he said, “simply because we haven’t looked enough”.
– Washington Post
