New cases of brain-invading worms found in Southeastern US
Rat lungworm has previously been found in Europe, Hawaii, and China. While it can be transmitted to humans, most get mild to no symptoms.
Rat lungworm is a parasitic worm that humans can become infected with by eating infected snails and slugs. Most people get mild to no symptoms, but the parasite can infect people’s brains and cause headaches, neck stiffness, vomiting, and neurological issues – meningitis is a severe symptom of the infection.
Now, a new study has identified the spread of this infection in rats in the Southeastern United States.
Why should we be concerned?
The adult form of rat lungworm, the scientific name for which is Angiostrongylus cantonensis, is only found in rodents. Infected rodents can pass larvae of the worm through their feces onto other animals like snails and slugs. These intermediate hosts can then affect the human population if they eat a raw or undercooked-infected intermediate host.
Although rat lungworm has a reputation for being a rare infection, it took Hawaii by surprise in 2017 when the state reported 18 confirmed and three probable human cases of the A. cantonensis infection, reported Ars Technica. As per the state’s health department, Hawaii had three reported cases in 2022 and two in 2023. A few isolated incidents have been reported scarcely in Europe as well.
“[W]ith a foothold in Europe it could spread farther across the continent, potentially to more temperate regions, as has already occurred in Australia and the United States,” warned Spanish researchers in February this year. “Furthermore, as the climate warms, even more northern parts of Europe may become accessible to A. cantonensis, as seen in China.”
Seven of 33 rats had rat lungworm
The study’s sample size was 33 wild brown rats, from whom the researchers collected tissue samples of their brain, heart, liver, kidney, lung, spleen, skeletal muscle, skin, gastrointestinal tract, adrenal gland, and gonads. These rats were found dead from 2019 to 2022 in a zoological facility in Atlanta, Georgia.
The study identified seven of 33 rats to have evidence of the A. cantonensis lungworm infection after examination of the heart, pulmonary artery, and brain tissues.
The study says that A. cantonensis infections in rats were present much earlier than in 2019 in Georgia when the first positive rat was identified, as the rat lungworm was previously identified in the neighboring states of Florida and Alabama.
According to the US Centers for Disease Control and Prevention (CDC), most cases of A. cantonensis-associated eosinophilic meningitis originated from Southeast Asia and the Pacific Islands. The parasite has also been reported in Africa, the Caribbean, Australia, Hawaii, and recently the southern United States.
Through this study, the researchers wanted to understand the patterns through which A. cantonensis lungworm has been expanding in North America. This, the researchers believe, is critical to mitigating the risk to humans and other animals for infection.
The researchers further warn: “Medical and veterinary professionals throughout the southern United States should consider A. cantonensis infection in differential diagnoses of aberrant central nervous system larva migrans, eosinophilic meningitis, and meningoencephalitis.”
The study was published in the journal Emerging Infectious Diseases.
Study abstract:
Rat lungworm (Angiostrongylus cantonensis), a zoonotic parasite invasive to the United States, causes eosinophilic meningoencephalitis. A. cantonensis harbors in rat reservoir hosts and is transmitted through gastropods and other paratenic hosts. We discuss the public health relevance of autochthonous A. cantonensis cases in brown rats (Rattus norvegicus) in Atlanta, Georgia, USA.
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