Case in Nova Iguaçu raises alert for vector-borne meningitis

In epidemiological research, the Oswaldo Cruz Institute (IOC/Fiocruz) confirmed the presence of the so-called worm Angiostrongylus cantonensiscausing eosinophilic meningitis, in snails collected in the city of Nova Iguaçu, Baixada Fluminense. Identification was made by the IOC/FIOCRUZ Malignant Science Laboratory, which serves as the National Reference Laboratory for Schistosomiasis – Malignant Science.

The reference service was activated by the Municipal Health Department of Nova Iguaçu after the confirmation of a death due to the disease in the city, on April 22. Specialists from the Municipal Environmental Health Surveillance Supervision Service (SUFAM/Nova Iguaçu) and the IOC/FIOCRUZ Conchatology Laboratory collected snails at different points in the Ipiranga neighborhood, of the Cabuçu Regional Government Unit (URG Cabuçu), where the patient was infected.

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The worm causing the disease was discovered in an aquatic snail of the genus Pomacea, known as lolô or aruá. Detection was made through parasitological examination of molluscs and genetic sequencing of the parasite. A total of 22 molluscs were analysed. Pomacea maculata slugs were infected.

After the mollusk infection was confirmed, another IOC/Fiocruz team joined the epidemiological investigation in the city. The Laboratory of Biology and Parasitology of Mammals in Wild Reservoirs, which serves as a national reference in the classification and diagnosis of wild leishmaniasis reservoirs, has been activated by the Supervisory Authority of Environmental Health Surveillance of Nova Iguaçu.

Specialists from the Reference Service initiated a field investigation in the Ipiranga neighborhood with the aim of identifying animals that serve as reservoirs of A. cantonensis in the area. This activity was based on collaboration with the Clinical Research Laboratory on Skin Diseases in Companions of the Evandro Chagas National Institute of Infectious Diseases (INI/Fiocruz) and support from Suvam/Nova Iguaçu.

In total, 15 animals, including mice, opossums and cave rats, were collected. Tests are underway to confirm infection in mammals.

Disease course

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

The larvae are shed in the feces of mice and ingested by snails. Inside molluscs, they acquire a form capable of infecting vertebrate animals. Human infection occurs when people ingest an infected snail or the mucus it secretes, which contains the worm's larvae.

Headache is the most common symptom of the disease. Stiff neck and fever, common in other forms of meningitis, occur only in some cases of eosinophilic meningitis. Some patients also experience visual disturbances, nausea, vomiting, and persistent paresthesias (such as, for example, a tingling sensation or numbness).

In most cases, the patient recovers spontaneously. However, medical monitoring is important because some individuals develop serious conditions that may lead to death. Treatment seeks to reduce inflammation in the central nervous system and relieve pain, as well as prevent complications.

Due to its large proliferation and wide distribution in the country, the giant African snail plays an important role in the spread of eosinophilic meningitis. To combat this vector, it is recommended to collect snails manually, as follows: collect the snails using gloves or plastic bags to protect your hands; put them in a pot of boiling water for five minutes. Break the shells and bury them or throw them in the trash (the shells should not be disposed of entirely because they can accumulate water, becoming a breeding ground for the Aedes aegypti mosquito).

Other important precautions include: Do not eat raw or undercooked shellfish, including land snails, slugs, and aquatic snails; Wash fruits and vegetables well, leave them soaked for 30 minutes in a mixture with a liter of water and a tablespoon of bleach, and rinse them well with running water before eating them.

*With information from the Fiocruz portal.

Edited by: Mariana Pitassi