A parasite that normally lives in the lungs of rats can infect the human brain if it accidentally gets into contaminated food — and now the worm has taken over new territory in the U.S., Live Science reports.
The parasite, called rat lungworm (Angiostrongylus cantonensis), primarily infects humans in Southeast Asia and is endemic to Hawaii and the Pacific Islands. Considered invasive in the continental United States, the worm probably first reached the southeastern part of the country in the 1980s via rats arriving in New Orleans, Louisiana, on commercial ships. Since then, sporadic cases of human infection have been reported in various states, including Texas, Tennessee and Alabama.
Now, in a study conducted between 2019 and 2022, researchers have found lungworm in brown rats (Rattus norvegicus) in Atlanta, Georgia.
“Because A. cantonensis lungworm was previously identified in rats in the neighboring states of Florida and Alabama, A. cantonensis populations were likely present in Georgia much earlier than 2019, when the first positive rat was identified in Atlanta.” , the researchers wrote in a report published in Emerging Infectious Diseases, a journal published by the Centers for Disease Control and Prevention (CDC). This “suggests that this zoonotic parasite was introduced and established in a new area of the southeastern United States.”
The team examined tissues from 33 brown rats found dead at Zoo Atlanta between 2019 and 2022. In seven of the rats, or about 21 percent, roundworms were found in the heart, pulmonary arteries and brain tissue. Genetic analysis confirmed that A. cantonensis was in four of these samples, and the genetic sequences completely matched those of lungworms previously collected in Louisiana.
The worms of the remaining rats could not be identified due to “insufficient sample quality and DNA degradation,” the researchers noted. For this reason, other worm species cannot be ruled out, but the rats had lesions suggestive of A. cantonensis infections.
How can rat lungworms get into humans?
The adult parasites live in the lungs of rats and only infect rats, but according to the CDC, rats can pass the parasite larvae in their feces. Snails can then become infected by eating the larvae, and by consuming raw or undercooked snails, humans can become infected in turn.
“People can also become infected accidentally by consuming raw produce (such as lettuce) that contains a small snail or part of it,” the CDC warns. Additional animals such as freshwater prawns, crabs and frogs can also be infected with the larvae, and it is possible that eating these animals raw or undercooked poses a risk to humans, but this is not well established.
Once in humans, the worm can cause a rare brain infection called eosinophilic meningitis, the symptoms of which can include headache, neck stiffness, tingling or painful skin sensations, low fever, nausea and vomiting.
“Most A. cantonensis infections resolve spontaneously over time without specific treatment because the parasite cannot survive long in the human body,” notes the CDC. “Not infrequently, however, serious complications can occur, leading to neurological dysfunction or death.”
The good news is that you can avoid this infection by being aware of where lungworms live and by not ingesting raw or undercooked snails, freshwater shrimp, land crabs, frogs or lizards, or potentially infected vegetables or juices, the CDC advises. Vegetables should be washed thoroughly if eaten raw.