Cultural and Clinical Insights from an Outbreak of Eosinophilic Meningitis Caused by the Rat Lungworm (Angiostrongylus cantonensis) in South Brazil

ABSTRACT. Angiostrongylus cantonensis , or rat lungworm, is a neurotropic parasite that causes eosinophilic meningitis. Although classically transmitted through ingestion of contaminated produce or undercooked snails or slugs, ritual ingestion of slugs as part of spiritual ceremonies has not been well described as a transmission route. We report two cases of eosinophilic meningitis in previously healthy adult men in south Brazil who developed subacute neurological symptoms, including progressive lower limb weakness, hyperesthesia, and severe neuropathic pain. Cerebrospinal fluid (CSF) analysis revealed marked eosinophilia (27–35%) and elevated protein levels. One patient showed subtle leptomeningeal enhancement on magnetic resonance imaging (MRI). Both cases were serologically confirmed by ELISA and western blot for A. cantonensis in CSF. History-taking revealed a shared exposure event: the ingestion of raw slugs during a religious ritual. Both patients were treated with albendazole, ivermectin, and corticosteroids for 2 weeks, as well as gabapentin for neuropathic pain. Both patients demonstrated neurological recovery and were discharged with outpatient follow-up. Both patients had normal CSF parameters within 2 weeks. These cases highlight a culturally linked exposure route for A. cantonensis . Clinicians should consider eosinophilic meningitis in the differential diagnosis of subacute neurological syndromes in endemic areas, particularly when initial diagnoses (e.g., urinary tract infection, gout) do not explain the full clinical picture. Culturally sensitive history-taking and communication, especially when considering communities that are vulnerable to stigma and violence, is critical to help obtain relevant exposure history.