Parasitic Brain-Invading Worm That Originates in Southeast Asian Rats Detected in US: CDC
A publication of the U.S. Centers for Disease Control and Prevention, has published a study covering the evocatively named “rat lungworm,” known in scientific circles as Angiostrongylus cantonensis. As usual with such studies, there was some good news and some bad news.
The good news: It’s not fatal — usually.
The bad news: It’s apparently made its way from Asia, where it was first discovered, and appears to be in the U.S. to stay.
According to the study, published in this month’s issue of “Emerging Infectious Diseases,” the parasite has previously been found in Hawaii, then in Texas, Louisiana, Alabama and Florida — all coastal states, leading to the hypothesis that it made its way to our golden shores via nautical trade routes. The current study was conducted in Georgia.
The study was relatively small, finding the worms in only seven of the 33 rats studied. However, as the study was conducted on “wild brown rats found dead during 2019–2022 on the grounds of a zoological facility located in Atlanta,” the extended time period would point to Angiostrongylus cantonensis being pretty well established in the area.
Rat lungworm is zoonotic, meaning that it can be passed from animals to humans.
Some of the details of how rat lungworm spreads remain unknown, according to the study’s authors, but they suggest that human activity may be increasing or speeding that spread.
“[A]nthropogenic disturbance and climate-induced change in local food webs might be amplifying A. cantonensis transmission,” they wrote.
“Clearly, A. cantonensis lungworm in urban rat populations, gastropod intermediate hosts, and other paratenic hosts in the populous greater Atlanta area pose a possible threat to the health of humans and domestic, free-ranging, and captive animals,” the authors warned.
Adult worms typically live in blood vessels near a rat’s lungs (hence the name), and lay eggs there, according to Ars Technica. Larvae then get coughed up from the lungs by the rat, which then — being a rat — eats them. Later, slugs and snails feeding on rat feces sometimes ingest the larvae, and are in turn eaten by rats, move to the mammal’s central nervous system and then brain, and later move to the lungs, where the cycle begins anew.
Humans eating undercooked snails or improperly washed salad can accidentally ingest the larvae, too, or might swallow them second-hand by eating undercooked frogs, shrimp, crabs or other animals that have feasted on infected snails or slugs.
In a human, rat lungworms do the same thing they typically do in their rodent hosts — move to the central nervous system and brain. Often, they cause no harm, or only mild, temporary symptoms.
However, sometimes things can be much, much worse.
More severe cases can “start with nonspecific symptoms like headache, light sensitivity, and insomnia and develop into neck stiffness and pain, tingling or burning of the skin, double vision, bowel or bladder difficulties, and seizures,” according to Ars Technica.
“In severe cases, it can cause nerve damage, paralysis, coma, and even death,” the outlet reported, under the not-at-all-alarming headline “Worm that jumps from rats to slugs to human brains has invaded Southeast US.”
According to the CDC, it can also cause eosinophilic meningitis or eye problems.
You can learn more from the CDC’s video on the subject:
There’s been some evidence of rat lungworms completing their life cycle in human lungs, but for the most part it’s thought that our immune systems are too powerful for the parasite to overcome.
Anti-parasitic drugs have proved ineffective in humans against the lungworms, Ars Technica wrote, and in fact have on occasion made symptoms worse.
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