After two people in Guangzhou, China, were admitted to the hospital with headaches and other neurological symptoms, doctors pinpointed an infection with a unusual backstory: They had eaten raw centipedes, according to a report published Monday in the American Journal of Tropical Medicine and Hygiene.
The first patient, a 78-year-old woman, came to the hospital in November 2012 with a headache, sleepiness and cognitive impairment. Weeks later, her 46-year-old son also came to the hospital with a headache that had lasted for more than 20 days. Both patients had stiff necks, a sign of possible meningitis. Scans showed two suspicious spots in the woman's brain, and one nodule in the man's right lung.
Both patients had something in common: They had eaten raw centipedes from a vegetable market in Guangzhou.
Lab tests confirmed that they were infected with rat lungworm, otherwise known as Angiostrongylus cantonensis, which had caused a type of meningitis.
The parasite can fully mature in rats, not humans. "So when it gets in a human, it can get lost, and it will go to the brain, and it'll stay there," Heather Stockdale Walden, an assistant professor in the department of infectious diseases and pathology at the University of Florida, previously told CNN.
"When it gets to the brain, you can have eosinophilic meningitis," she said, referring to an inflammation of the thin membrane covering the spinal cord and brain.
Humans have become infected with the parasite by eating contaminated plants and animals -- including snails, slugs and even monitor lizards. But it was not known to be caused by eating centipedes, which have long been used in Chinese traditional medicine.
Still, it is rare to eat them raw, and "centipedes are not a normal diet," Dr. Lingli Lu, one of the report's authors and a neurologist at Zhujiang Hospital in Guangzhou, told CNN in an e-mail.
"The male patient believes eating raw centipedes are good for health," and so he ate some and gave some to his mother, Lu said.
To confirm that it could have been the centipedes, the researchers purchased 20 of them from the same market where the two patients had gotten theirs. They found rat lungworm larvae in seven of the specimens -- an average of 56 larvae per centipede.
"To our knowledge, this is the first report of A. cantonensis infection through the consumption of centipedes," they wrote.
"We do know that people can acquire the parasite by consuming raw or undercooked snails and slugs," Janice Okubo, a spokeswoman for the Hawaii State Department of Health, told CNN last year when the state saw a number of cases.
More than 140 species of mollusks, such as snails and slugs, have been found to be potential intermediate hosts in nature and in scientific experiments, according to the authors of the new report.
Other animals that feast on these snails and slugs, including some frogs and fish, may also become infected. But as the name of the parasite suggests, the rat is the definitive host.
The parasitic worm, after being ingested by rats, makes its way from the intestine to the bloodstream, and then to the brain. They molt and mature in the brain and migrate back down to the lung's arteries, where adult worms are found. An adult female may lay 15,000 eggs per day.
Rats cough up these worms and subsequently swallow them. This is how the parasites tend to end up back in rats' fecal matter, where they are then eaten by slugs or snails -- and so the cycle continues.
In humans, the parasite can't survive for long, so most infections eventually resolve on their own. But in rare cases, it can cause serious complications and even death, according to the US Centers for Disease Control and Prevention.
"Angiostrongylus cantonensis can present differently in adults and children. So usually, in adults, one of the main things that you hear complaint of is a headache," Walden said. She added that adults commonly report neck stiffness, nausea and vomiting.
"In children, it's more the nausea and vomiting, not so much the headache," she said. Children will also run fevers and feel abdominal pain more than adults.
The ingested parasite "can also move to the eye, and you can get ocular Angiostrongylus," Walden said. "If the parasite goes to the eye, sometimes you can surgically remove it."
People do not become contagious, so they cannot transmit the infection to someone else.
The patients in the new report recovered well after 15 days of treatment, which included an antiparasitic drug and a steroid, the authors wrote.
Doctors generally look for clues and base their diagnoses on possible exposure to the parasite, through food or water, while living in or visiting an endemic region. Over 2,800 cases have been reported in about 30 countries, most of them in parts of Asia and the Pacific Islands, with fewer cases appearing in the Caribbean and Africa.
The CDC recommends washing vegetables thoroughly and boiling any frogs or snails you might be eating for three to five minutes. According to the agency, you may also want to cover any beverages to thwart any snails or slugs on a mission.