Brazil officials warn of rat lungworm in snails after death reported in Rio de Janeiro state

The Oswaldo Cruz Institute (IOC/Fiocruz) has issued a warning about the transmission of meningitis by snails.

They confirmed the presence of Angiostrongylus cantonensis, aka rat lungworm, which causes eosinophilic meningitis, in a snail collected in the city of Nova Iguaçu, in Baixada Fluminense, a region in the state of Rio de Janeiro, in southeastern Brazil.

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The concern arose after the death of a patient on April 22 in the municipality of Nova Iguaçu.

The worm that causes the disease was detected in an aquatic snail of the genus Pomacea, popularly known as lolô or aruá. Detection was performed through parasitological examination of the mollusks and genetic sequencing of the parasite. A total of 22 mollusks were analyzed. One mollusk of the species Pomacea maculata was infected. 

In total, 15 animals were collected, including rats, opossums and cavies. Analysis is ongoing to confirm the infection in the mammals. 

There has not been a case of rat lungworm transmitted by snails in the state of Rio since 2014.

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Meningitis transmitted by snails is called eosinophilic meningitis. The disease is caused by the worm Angiostrongylus cantonensis. In the life cycle of this worm, rodents (e.g. urban rats) act as hosts for the adult forms of the parasite, which reproduce in the animals' bodies and produce larvae (young forms of the worm). 

The larvae are eliminated in the feces of rats and ingested by snails. Inside the mollusks, they acquire the form capable of infecting vertebrate animals. Human infection occurs when people ingest an infected snail or the mucus released by it, which contains the worm larvae. 

Headache is the most common symptom of the disease. Neck stiffness and fever, which are common in other forms of meningitis, occur only in some cases of eosinophilic meningitis. Some patients also experience visual disturbances, nausea, vomiting, and persistent paresthesia (such as a tingling or numbness sensation). 

In most cases, the patient recovers spontaneously. However, medical monitoring is important because some individuals develop serious conditions that can lead to death. Treatment aims to reduce inflammation in the central nervous system and relieve pain, in addition to preventing complications. 

Officials remind the public not to eat raw or undercooked mollusks, including land snails, slugs and aquatic snails; and wash fruits and vegetables well, leaving them to soak for 30 minutes in a mixture of one liter of water and one tablespoon of bleach, rinsing them well in running water before consumption.